MAX5978ETJ+ - Maxim Integrated

_______________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

19-5328; Rev 0; 7/10

General Description

The MAX5978 hot-swap controller provides complete pro-

tection for systems with a supply voltage from 0 to 16V.

The device includes four programmable LED outputs.

The IC provides two programmable levels of overcur-

rent circuit-breaker protection: a fast-trip threshold for

a fast turn-off, and a lower slow-trip threshold for a

delayed turn-off. The maximum overcurrent circuit-

breaker threshold range is set with a trilevel logic input

(IRNG), or by programming through the I2C interface.

The IC is an advanced hot-swap controller that monitors

voltage and current with an internal 10-bit ADC, which is

continuously multiplexed to convert the output voltage

and current at 10ksps. Each 10-bit sample is stored in an

internal circular buffer so that 50 past samples of each

signal can be read back through the I2C interface at any

time or after a fault condition.

The device includes five user-programmable digital

comparators to implement overcurrent warning and two

levels of overvoltage/undervoltage detection. When mea-

sured values violate the programmable limits, an external

ALERT output is asserted. In addition to the ALERT sig-

nal, the IC can be programmed to deassert the power-

good signal and/or turn off the external MOSFET.

The IC features four I/Os that can be independently

configured as general-purpose input/outputs (GPIOs) or

as open-drain LED drivers with programmable blinking.

These four I/Os can be configured for any mix of LED

driver or GPIO function.

The device is available in a 32-pin thin QFN-EP pack-

age and operates over the -40NC to +85NC extended

temperature range.

Ordering Information

Features

S Hot-Swap Controller Operates from 0 to 16V

S 10-Bit ADC Monitors Load Voltage and Current

S Circular Buffers Store 5ms of Current and Voltage

Measurements

S Internal Charge Pump Generates n-Channel

MOSFET Gate Drive

S Internal 500mA Gate Pulldown Current for Fast

Shutdown

S VariableSpeed/Bilevel™ Circuit-Breaker

Protection

S Precision-Voltage Enable Input

S Alert Output Indicates Fault and Warning

Conditions

S Open-Drain Power-Good Output with

Programmable Polarity

S Open-Drain Fault Output

S Four Open-Drain General-Purpose Outputs Sink

25mA to Directly Drive LEDs

S Programmable LED Flashing Function

S Latched-Off Fault Management

S 400kHz I2C Interface

S Small, 5mm x 5mm, 32-Pin TQFN-EP Package

Applications

Blade Servers

DC Power Metering

Disk Drives/DASD/Storage Systems

Soft-Switch for ASICs, FPGAs, and

Microcontrollers

Network Switches/Routers

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

VariableSpeed/Bilevel is a trademark of Maxim Integrated

Products, Inc.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX5978ETJ+ -40NC to +85NC32 TQFN-EP*

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

IN, SENSE, MON, GATE to AGND ...................... -0.3V to +30V

LED_ to AGND .....................................................-0.3V to +16V

PG, ON, ALERT, FAULT, SDA, SCL to AGND .......-0.3V to +6V

REG, DREG, IRNG, MODE, PROT, A_ to AGND ...-0.3V to +4V

REG to DREG ......................................................-0.3V to +0.3V

HWEN, POL to AGND ............................-0.3V to (VREG + 0.3V)

GATE to MON ........................................................-0.3V to +6V

GND, DGND to AGND ........................................-0.3V to +0.3V

SDA, ALERT Current ...................................... -20mA to +50mA

LED_ Current ................................................ -20mA to +100mA

GATE, MON, GND Current .............................................750mA

All Other Pins Input/Output Current ..................................20mA

Continuous Power Dissipation (TA = +70NC)*

32-Pin TQFN (derate 34.5mW/NC above +70NC) ..... 2759mW*

Junction-to-Ambient Thermal Resistance (BJA) (Note 1) .....+29NC/W

Operating Temperature Range ........................ -40NC to +85NC

Junction Temperature .................................................. +150NC

Storage Temperature Range ......................... -65NC to +150NC

Lead Temperature (soldering, 10s) ...............................+300NC

Soldering Temperature (reflow) .....................................+260NC

ELECTRICAL CHARACTERISTICS

(VIN = 2.7V to 16V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VIN = 3.3V and TA = +25NC.) (Note 2)

ABSOLUTE MAXIMUM RATINGS

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.

*As per JEDEC51 Standard (Multilayer Board).

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Input Voltage Range VIN 2.7 16 V

Hot-Swap Voltage Range 0 16 V

Supply Current IIN 2.5 4 mA

Internal LDO Output Voltage REG IREG = 0 to 5mA, VIN = 2.7V to 16V 2.49 2.53 2.6 V

Undervoltage Lockout UVLO VIN rising 2.6 V

Undervoltage-Lockout

Hysteresis UVLOHYS 100 mV

CURRENT-MONITORING FUNCTION

MON, SENSE Input Voltage

Range 0 16 V

SENSE Input Current VSENSE, VMON = 16V 32 75 FA

MON Input Current VSENSE, VMON = 16V 180 280 FA

Current Measurement LSB

Voltage

25mV range 24.34

50mV range 48.39

100mV range 96.77

Current Measurement Error

(25mV Range)

VMON = 0V VSENSE - VMON = 5mV -6.57 +6.22

%FS

VSENSE - VMON = 20mV -6.71 +6.82

VMON =

2.5V to 16V

VSENSE - VMON = 5mV -9.71 +8.92

VSENSE - VMON = 20mV -10.24 +9.36

Current Measurement Error

(50mV Range)

VMON = 0V VSENSE - VMON = 10mV -4.24 +3.78

%FS

VSENSE - VMON = 40mV -4.53 +5.36

VMON =

2.5V to 16V

VSENSE - VMON = 10mV -4.50 +4.00

VSENSE - VMON = 40mV -4.20 +4.50

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 2.7V to 16V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VIN = 3.3V and TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Current Measurement Error

(100mV Range)

VMON = 0V VSENSE - VMON = 20mV -2.70 +2.43

%FS

VSENSE - VMON = 80mV -3.63 +4.56

VMON =

2.5V to 16V

VSENSE - VMON = 20mV -3.14 +3.19

VSENSE - VMON = 80mV -3.80 +3.93

Fast Current-Limit Threshold

Error (25mV Range)

VMON = 0V Circuit breaker, DAC = 102 -2.106 +0.888

Circuit breaker, DAC = 255 -2.986 +0.641

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -3.000 +1.000

Circuit breaker, DAC = 255 -3.500 +1.500

Fast Current-Limit Threshold

Error (50mV Range)

VMON = 0V Circuit breaker, DAC = 102 -3.1188 +0.926

Circuit breaker, DAC = 255 -4.873 +0.3421

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -3.2668 +0.9228

Circuit breaker, DAC = 255 -4.7 +1.0212

Fast Current-Limit Threshold

Error (100mV Range)

VMON = 0V Circuit breaker, DAC = 102 -4.7987 +1.1812

Circuit breaker, DAC = 255 -8.9236 +0.202

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -4.9991 +0.6374

Circuit breaker, DAC = 255 -8.262 +1

Slow Current-Limit Threshold

Error (25mV Range)

VMON = 0V Circuit breaker, DAC = 102 -1.7965 +1.5496

Circuit breaker, DAC = 255 -1.86 +1.5916

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -2.149 +1.9868

Circuit breaker, DAC = 255 -2.2285 +1.9982

Slow Current-Limit Threshold

Error (50mV Range)

VMON = 0V Circuit breaker, DAC = 102 -2.3992 +1.8723

Circuit breaker, DAC = 255 -2.5146 +2.1711

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -2.4716 +2.181

Circuit breaker, DAC = 255 -2.7421 +2.1152

Slow Current-Limit Threshold

Error (100mV Range)

VMON = 0V Circuit breaker, DAC = 102 -3.3412 +2.989

Circuit breaker, DAC = 255 -3.8762 +3.6789

VMON =

2.5V to 16V

Circuit breaker, DAC = 102 -3.2084 +2.7798

Circuit breaker, DAC = 255 -3.8424 +2.6483

Fast Circuit-Breaker

Response Time tFCB Overdrive = 10% of current-sense range 2 Fs

Slow Current-Limit Response

Time tSCB

Overdrive = 4% of current-sense range 2.4

msOverdrive = 8% of current-sense range 1.2

Overdrive = 16% of current-sense range 0.8

THREE-STATE INPUTS

A1, A0, IRNG, MODE, PROT

Low Current IIN_LOW Input voltage = 0.4V -40 FA

A1, A0, IRNG, MODE, PROT

High Current IIN_HIGH Input voltage = VREG - 0.2V 40 FA

A1, A0, IRNG, MODE, PROT

Open Current IFLOAT Maximum source/sink current for open

state -4 +4 FA

A1, A0, IRNG, MODE, PROT

Low Voltage Relative to AGND 0.4 V

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 2.7V to 16V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VIN = 3.3V and TA = +25NC.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

A1, A0, IRNG, MODE, PROT

High Voltage Relative to VREG -0.24 V

TWO-STATE INPUTS

HWEN, POL Input Logic Low

Voltage 0.4 V

HWEN, POL Input Logic High

Voltage VREG - 0.4 V

HWEN, POL Input Current -1 +1 FA

ON Input Voltage VON 0.582 0.592 0.602 V

ON Input Hysteresis VONHYS 4 %

ON Input Current -100 +100 nA

TIMING

MON-to-PG Delay Register configurable (see Tables 30a and

30b)

100

200

400

CHARGE PUMP (GATE)

Charge-Pump Output Voltage Relative to VMON, IGATE = 0V 4.5 5.3 5.5 V

Charge-Pump Output Source

Current 4 5 6 FA

GATE Discharge Current VGATE - VMON = 2V 500 mA

OUTPUT (FAULT, PG, ALERT)

Output-Voltage Low ISINK = 3.2mA 0.2 V

Output Leakage Current 1 FA

LED INPUT/OUTPUT

LED_ Input Threshold Low

Level VIL 0.4 V

LED_ Input Threshold High

Level VIH 1.4 V

LED_ Output Low VOH ILED_ = 25mA 0.7 V

LED_ Input Leakage Current

(Open Drain) IGPIO_IX VLED_ = 16V -1 +1 FA

LED_ Weak Pullup Current IPU_WEAK VLED_ = VIN - 0.65V 2 FA

ADC PERFORMANCE

Resolution 10 Bits

Maximum Integral

Nonlinearity INL 1 LSB

ADC Total Monitoring Cycle

Time 95 100 110 Fs

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

ELECTRICAL CHARACTERISTICS (continued)

(VIN = 2.7V to 16V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VIN = 3.3V and TA = +25NC.) (Note 2)

Note 2: All devices 100% production tested at TA = +25NC. Limits over the temperature range are guaranteed by design.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MON LSB Voltage

16V range 15.23 15.49 15.69

8V range 7.655 7.743 7.811

4V range 3.811 3.875 3.933

2V range 1.899 1.934 1.966

MON Code 000H to 001H

Transition Voltage

16V range 10 25 41

8V range 4.7 12 21

4V range 2 6 12

2V range 0.5 3 5.5

I2C INTERFACE

Serial-Clock Frequency fSCL 400 kHz

Bus Free Time Between

STOP and START Conditions tBUF 1.3 Fs

START Condition Setup Time tSU:STA 0.6 Fs

START Condition Hold Time tHD:STA 0.6 Fs

STOP Condition Setup Time tSU:STO 0.6 Fs

Clock High Period tHIGH 0.6 Fs

Clock Low Period tLOW 1.3 Fs

Data Setup Time tSU:DAT 100 ns

Data Hold Time tHD:DAT Transmit 100 ns

Receive 300 900

Output Fall Time tOF CBUS = 10pF to 400pF 250 ns

Pulse Width of Spike

Suppressed tSP 50 ns

SDA, SCL Input High Voltage VIH 1.8 V

SDA, SCL Input Low Voltage VIL 0.8 V

SDA, SCL Input Hysteresis VHYST 0.22 V

SDA, SCL Input Current -1 +1 FA

SDA, SCL Input Capacitance 15 pF

SDA Output Voltage VOL ISINK = 4mA 0.4 V

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Typical Operating Characteristics

(VIN = 3.3V, TA = +25NC, unless otherwise noted.)

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX5978 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

1412108642

2.35

2.40

HOT-SWAP CHANNEL ON

HOT-SWAP CHANNEL OFF

2.45

2.50

2.30

0 16

SUPPLY CURRENT vs. TEMPERATURE

MAX5978 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

2.0

-40 85

GATE-DRIVE VOLTAGE vs. VMON

MAX5978 toc03

VMON (V)

GATE-DRIVE VOLTAGE (V)

14122 4 6 8 10

4.85

4.90

4.95

5.00

5.05

5.10

5.15

VGATE REFERRED TO VMON

5.20

4.80

0 16

GATE-DRIVE VOLTAGE vs. VIN

MAX5978 toc04

VIN (V)

(VGATE - VMON) (V)

1412108642

4.90

4.95

5.00

5.05

VMON = 3.3V

VMON = 12V

5.10

4.85

0 16

GATE-DRIVE CURRENT

vs. (VGATE - VMON)

MAX5978 toc05

(VGATE - VMON) (V)

GATE-DRIVE CURRENT (µA)

4.54.03.0 3.51.0 1.5 2.0 2.50.5

0 5.0

GATE-DRIVE DISCHARGE CURRENT

vs. (VGATE - VMON)

MAX5978 toc06

(VGATE - VMON) (V)

GATE-DRIVE DISCHARGE CURRENT (A)

4.54.03.0 3.51.0 1.5 2.0 2.50.5

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5.0

SLOW-COMPARATOR TURN-OFF TIME

vs. VOLTAGE OVERDRIVE

MAX5978 toc07

(VSENSE - VMON) - VTH,ST (mV)

TURN-OFF TIME (ms)

4321

0.50

1.00

1.50

2.00

2.50

3.00

0 5

25mV SENSE RANGE,

DAC = 191, VTH,ST = 9.36mV

SLOW-COMPARATOR THRESHOLD

VOLTAGE ERROR vs. TEMPERATURE

MAX5978 toc08

TEMPERATURE (°C)

THRESHOLD VOLTAGE ERROR (%)

603510-15

-8

-6

-4

-2

-10

-40 85

50mV SENSE RANGE

100mV SENSE RANGE

25mV SENSE RANGE

ON THRESHOLD VOLTAGE

vs. TEMPERATURE

MAX5978 toc09

TEMPERATURE (°C)

ON THRESHOLD VOLTAGE (V)

603510-15

0.51

0.52

0.53

0.54

0.55

0.56

0.57

0.58

0.59

0.60

0.50

-40 85

RISING

FALLING

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Typical Operating Characteristics (continued)

(VIN = 3.3V, TA = +25NC, unless otherwise noted.)

STARTUP WAVEFORM

MAX5978 toc10

VMON

5V/div

VON

2V/div

VGATE

5V/div

VPG

5V/div

ILOAD

2A/div

10ms/div

TURN-OFF WAVEFORM

(SLOW-COMPARATOR FAULT)

MAX5978 toc11

VMON_

10V/div

ILOAD

2A/div

VGATE

10V/div

VFAULT

5V/div

400µs/div

TURN-OFF WAVEFORM (FAST-COMPARATOR

FAULT/SHORT-CIRCUIT RESPONSE)

MAX5978 toc12

VMON

10V/div

ILOAD

5A/div

VGATE

10V/div

VFAULT

5V/div

100µs/div

VOLTAGE BUFFER vs. TIME

MAX5978 toc13

TIME (ms)

VOLTAGE BUFFER (V)

2.01.5-2.0 -1.5 -1.0 0 0.5-0.5 1.0

16 CIRCULAR BUFFER CONTENT AT SLOW-TRIP

FAULT MON = 16V, CURRENT SENSE = 50mV

-2.5 2.5

SLOW-COMPARATOR FAULT EVENT

MAX5978 toc14

VMON

10V/div

ILOAD

2A/div

VGATE

10V/div

VFAULT

5V/div

400µs/div

VOLTAGE ADC ACCURACY

vs. MON VOLTAGE

MAX5978 toc15

VMON (V)

VOLTAGE ADC ACCURACY (%FS)

3.53.02.0 2.51.0 1.50.5

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0

0 4.0

MON_ VOLTAGE RANGE = 4V

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Typical Operating Characteristics (continued)

(VIN = 3.3V, TA = +25NC, unless otherwise noted.)

INPUT LEAKAGE CURRENT

vs. MON VOLTAGE

MAX5978 toc20

VMON (V)

INPUT-LEAKAGE CURRENT (µA)

14128 104 62

100

120

140

160

180

200

0 16

IMON

ISENSE

STARTUP INTO SHORT LOAD

MAX5978 toc19

VMON

1V/div

VON

5V/div

ILOAD

5A/div

VGATE

2V/div

VFAULT

5V/div

4ms/div

VOLTAGE BUFFER vs. TIME

MAX5978 toc18

TIME (ms)

VOLTAGE BUFFER (V)

2.01.50.5 1.0-1.5 -1.0 -0.5 0-2.0

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

-0.5

-2.5 2.5

VOLTAGE DATA AT SHORT CIRCUIT ON

POWER-UP DEFAULT SETTING VMON = 16V

CURRENT BUFFER vs. TIME

MAX5978 toc17

TIME (ms)

CURRENT BUFFER (A)

2.01.50.5 1.0-1.5 -1.0 -0.5 0-2.0

DEFAULT SETTING

-2.5 2.5

CURRENT ADC ACCURACY

vs. (VSENSE - VMON)

MAX5978 toc16

(VSENSE - VMON) (mV)

CURRENT ADC ACCURACY (%FS)

22.520.015.0 17.55.0 7.5 10.0 12.52.5

-4

-3

-2

-1

-5

0 25.0

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Pin Configuration

Pin Description

MAX5978

TQFN

TOP VIEW

REG

BIAS

IRNG

I.C.

ALERT

SCL

HWEN

SDA

FAULT

1 2

LED4

4 5 6 7

2324 22 20 19 18

LED3

GND

LED2

LED1

GND

GATE

AGND PG

31 10

I.C. MON

32 9

I.C. SENSE

I.C.

26 15 POL

I.C.

25 16 DREG

PROT ON

DGND

PIN NAME FUNCTION

1 IRNG Three-State Current-Sense Range Selection Input. Set the circuit-breaker threshold range by

connecting to DGND, DREG, or leave unconnected.

2 IN Power-Supply Input. Connect to a voltage from 2.7V to 16V. Bypass IN to AGND with a 1FF

ceramic capacitor.

3 AGND Analog Ground. Connect all GND and DGND to AGND externally using a star connection.

4 REG Internal Regulator Output. Bypass REG to ground with a 1FF ceramic capacitor. Connect only to

DREG and logic-input pullup resistors. Do not use to power external circuitry.

5 BIAS BIAS Input. Connect BIAS to REG.

6 A1 Three-State I2C Address Input 1

7 A0 Three-State I2C Address Input 0

8 PROT Protection Behavior Input. Three-state input sets one of three different response options for

undervoltage and overvoltage events.

9 SENSE Current-Sense Input. Connect SENSE to the source of an external MOSFET and to one end of

RSENSE.

10 MON Voltage-Monitoring Input

11 GATE Gate-Drive Output. Connect to the gate of an external n-channel MOSFET.

12 GND Gate-Discharge Current Ground Return. Connect all GND and DGND to AGND externally using

a star connection.

13 LED1 LED1 Driver

14 LED2 LED2 Driver

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Pin Description (continued)

PIN NAME FUNCTION

15 POL Polarity Select Input. Connect POL to DREG for an active-high power-good (PG) output, or con-

nect POL to GND for active-low PG output.

16 DREG Logic Power-Supply Input. Connect to REG externally through a 10I resistor and bypass to

DGND with a 1FF ceramic capacitor.

17 ON Precision Turn-On Input

18 FAULT Active-Low Open-Drain Fault Output. FAULT asserts low if an overcurrent event occurs.

19 SDA I2C Serial Data Input/Output

20 SCL I2C Serial Clock Input

21 ALERT Open-Drain Alert Output. ALERT goes low during a fault to notify the system of an impending

failure.

22 PG Open-Drain Power-Good Output

23, 26, 27,

31, 32 I.C. Internally Connected. Connect to ground.

24 HWEN

Hardware Enable Input. Connect to REG or DGND. State is read upon power-up as VIN crosses

the UVLO threshold and sets enable register bits with this value. After UVLO, this input becomes

inactive until power is cycled.

25 DGND Digital Ground. Connect all GND and DGND to AGND externally using a star connection.

28 LED4 LED Driver 4

29 LED3 LED Driver 3

30 GND Ground

— EP Exposed Pad. EP is internally grounded. Connect EP to the ground plane using a star connection.

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Typical Operating Circuit

IRNG

SENSE

GATE

MON

DGND

AGND

REG

A0 A1

SCL

SDA

POL

PROT

HWEN

GND

DREG

LED4

LED3

LED1

LED2

BIAS

µP

I/O

VSVIN = 2.7V TO 16V

INT

SDA

SCLK

I/O

SETTING

CONFIGURATION

SETTINGS

VCC

V+

RSENSE

R1ON

R2ON

RLED2 RLED1

RLED3 RLED4

10I

4.7kI

VCC

1µF

FAULT

ALERT

MAX5978

LOAD

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Functional Diagram

MAX5978

DREG

SCOMP

FCOMP

ATTENUATOR

CS AMP

MUX

OSCILLATOR

UVLO

LDO IREF

I2C

ALERT

SCL

SDA

BIAS

PROT

POL

IRNG

SENSE

MON

GATE

GND

REG

HWEN

LED_

FAULT

2MHz

5µA

FROM

CONFIGURATION

REGISTERS

DAC SELECT

REF

GATE

PULLDOWN

CHARGE

PUMP

VOLTAGE

SCALING

10-BIT ADC

(SAR)

CIRCULAR

BUFF

DGNDAGND

LOGIC

BLOCK

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Detailed Description

The MAX5978 includes a set of registers that are

accessed through the I2C interface. Some of the reg-

isters are read only and some of the registers are read

and write registers that can be updated to configure the

device for a specific operation. See Tables 1a and 1b for

the register maps.

Hot-Swap Channel On-Off Control

Depending on the configuration of the EN1 and EN2

bits, when VIN is above the VUVLO threshold and the ON

input reaches its internal threshold, the device turns on

the external n-channel MOSFET for the hot-swap chan-

nel, allowing power to flow to the load. The channel is

enabled depending on the output of a majority function.

EN1, EN2, and ON are the inputs to the majority function

and the channel is enabled when two or more of these

inputs are 1:

(Channel enabled) = (EN1 x EN2) + (EN1 x ON) +

(EN2 x ON)

Inputs ON and EN2 can be set externally; the initial state

of the EN2 bit in register chxen is set by the state of the

HWEN input when VIN rises above VUVLO. The ON input

connects to an internal precision analog comparators

with a 0.6V threshold. Whenever VON is above 0.6V, the

ON bit in register status1[0] is set to 1. Inputs EN1 and

EN2 can be set using the I2C interface; the EN1 bit has

a default value of 0. This makes it possible to enable or

disable the hot-swap channel with or without using the

I2C interface (see Tables 2, 3a, and 3b).

Table 1a. Register Address Map (Channel Specific)

NAME DESCRIPTION REGISTER

NUMBER

RESET

VALUE

READ/

WRITE

adc_cs_msb High 8 bits ([9:2]) of latest current-signal ADC result 0x00 0x00 R

adc_cs_lsb Low 2 bits ([1:0]) of latest current-signal ADC result 0x01 0x00 R

adc_mon_msb High 8 bits ([9:2]) of latest voltage-signal ADC result 0x02 0x00 R

adc_mon_lsb Low 2 bits ([1:0]) of latest voltage-signal ADC result 0x03 0x00 R

min_cs_msb High 8 bits ([9:2]) of current-signal minimum value 0x08 0xFF R

min_cs_lsb Low 2 bits ([1:0]) of current-signal minimum value 0x09 0x03 R

max_cs_msb High 8 bits ([9:2]) of current-signal maximum value 0x0A 0x00 R

max_cs_lsb Low 2 bits ([1:0]) of current-signal maximum value 0x0B 0x00 R

min_mon_msb High 8 bits ([9:2]) of voltage-signal minimum value 0x0C 0xFF R

min_mon_lsb Low 2 bits ([1:0]) of voltage-signal minimum value 0x0D 0x03 R

max_mon_msb High 8 bits ([9:2]) of voltage-signal maximum value 0x0E 0x00 R

max_mon_lsb Low 2 bits ([1:0]) of voltage-signal maximum value 0x0F 0x00 R

uv1th_msb High 8 bits ([9:2]) of undervoltage warning (UV1) threshold 0x1A 0x00 R/W

uv1th_lsb Low 2 bits ([1:0]) of undervoltage warning (UV1) threshold 0x1B 0x00 R/W

uv2th_msb High 8 bits ([9:2]) of undervoltage critical (UV2) threshold 0x1C 0x00 R/W

uv2th_lsb Low 2 bits ([1:0]) of undervoltage critical (UV2) threshold 0x1D 0x00 R/W

ov1thr_msb High 8 bits ([9:2]) of overvoltage warning (OV1) threshold 0x1E 0xFF R/W

ov1thr_lsb Low 2 bits ([1:0]) of overvoltage warning (OV1) threshold 0x1F 0x03 R/W

ov2thr_msb High 8 bits ([9:2]) of overvoltage critical (OV2) threshold 0x20 0xFF R/W

ov2thr_lsb Low 2 bits ([1:0]) of overvoltage critical (OV2) threshold 0x21 0x03 R/W

oithr_msb High 8 bits ([9:2]) of overcurrent warning threshold 0x22 0xFF R/W

oithr_lsb Low 2 bits ([1:0]) of overcurrent warning threshold 0x23 0x03 R/W

dac_fast Fast-comparator threshold DAC setting 0x2E 0xBF R/W

cbuf_ba_v Base address for block read of 50-sample voltage-signal data buffer 0x46 — R

cbuf_ba_i Base address for block read of 50-sample current-signal data buffer 0x47 — R

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Table 1b. Register Address Map (General)

Table 2. chxen Register Format

NAME DESCRIPTION ADDRESS

(HEX CODE)

RESET

VALUE

READ/

WRITE

mon_range MON input range setting 0x18 0x00 R/W

cbuf_chx_store Selective enabling of circular buffer 0x19 0x0F R/W

ifast2slow Current threshold fast-to-slow ratio setting 0x30 0x0F R/W

status0 Slow-trip and fast-trip comparators status register 0x31 0x00 R

status1 PROT, MODE, and ON inputs status register 0x32 — R

status2 Fast-trip threshold maximum range setting bits, from IRNG three-

state input 0x33 — R/W

status3 LATCH, POL, ALERT, and PG status register 0x34 — R

fault0 Status register for undervoltage detection (warning or critical) 0x35 0x00 R/C

fault1 Status register for overvoltage detection (warning or critical) 0x36 0x00 R/C

fault2 Status register for overcurrent detection (warning) 0x37 0x00 R/C

pgdly Delay setting between MON measurement and PG assertion 0x38 0x00 R/W

fokey Load register with 0xA5 to enable force-on function 0x39 0x00 R/W

foset Register that enables force-on function 0x3A 0x00 R/W

chxen Channel enable bits 0x3B — R/W

dgl_i OC deglitch enable bits 0x3C 0x00 R/W

dgl_uv UV deglitch enable bits 0x3D 0x00 R/W

dgl_ov OV deglitch enable bits 0x3E 0x00 R/W

cbufrd_hibyonly Circular buffers readout mode: 8 bit or 10 bit 0x3F 0x0F R/W

cbuf_dly_stop Circular buffer stop delay; number of samples recorded to the circu-

lar buffer after channel shutdown 0x40 0x19 R/W

peak_log_rst Reset control bits for peak-detection registers 0x41 0x00 R/W

peak_log_hold Hold control bits for peak-detection registers 0x42 0x00 R/W

LED_flash LED flash/GPIO enable register 0x43 0x0F R/W

LED_ph_pu LED phase/weak pullup enable register 0x44 0x00 R/W

LED_state LED pins voltage state register (LED pins set open) 0x45 — R

Description: Channel enable bits

Resister Title: chxen

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused EN2 EN1 —

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Figure 1 shows the detailed logic operation of the hot-

swap enable signals EN1, EN2, and ON, as well as the

effect of various fault conditions.

An input undervoltage threshold control for enabling

the hot-swap channel can be implemented by placing

a resistive divider between the drain of the hot-swap

MOSFET and ground, with the midpoint connected to

ON. The turn-on threshold voltage for the channel is then:

VEN = 0.6V x (R1 + R2)/R2

The maximum rating for the ON input is 6V; do not

exceed this value.

Startup

When all conditions for channel turn-on are met, the

external n-channel MOSFET switch is fully enhanced

with a typical gate-to-source voltage of 5V to ensure

a low drain-to-source resistance. The charge pump at

the GATE driver sources 5FA to control the output volt-

age turn-on voltage slew rate. An external capacitor

can be added from GATE to GND to further reduce the

voltage slew rate. Placing a 1kI resistor in series with

this capacitance prevents the added capacitance from

increasing the gate turn-off time. Total inrush current is

the load current summed with the product of the gate-

voltage slew rate dV/dt and the load capacitance.

To determine the output dV/dt during startup, divide

the GATE pullup current IG(UP) by the gate-to-ground

capacitance. The voltage at the source of the external

MOSFET follows the gate voltage, so the load dV/dt is

the same as the gate dV/dt. Inrush current is the product

of the dV/dt and the load capacitance. The time to start

up tSU is the hot-swap voltage VS divided by the output

dV/dt.

Be sure to choose an external MOSFET that can handle

the power dissipated during startup. The inrush cur-

rent is roughly constant during startup and the voltage

drop across the MOSFET (drain to source) decreases

linearly as the load capacitance charges. The resulting

power dissipation is, therefore, roughly equivalent to a

single pulse of magnitude (VS x inrush current)/2 and

Table 3a. Register Function

Table 3b. status1 Register Format

ADDRESS BIT RANGE DESCRIPTION

0x32

[1:0]

ON input state

1 = ON above 600mV channel enable threshold

0 = ON below 600mV channel enable threshold

Bit 0: ON input state

Bit 1: unused

[4] Unused

[7:6]

Voltage critical behavior (PROT input)

00 = Assert ALERT upon UV/OV critical (same as UV/OV warning behavior)

01 = Assert ALERT and deassert PG upon UV/OV critical

10 = Assert ALERT, deassert PG, and shut down channel upon UV/OV critical

11 = (Not possible)

Description: Fault-detection behavior (three-state PROT input) and ON input status register

Resister Title: status1

RESET

VALUE

R R R R R R R R

prot[1] prot[0] — Unused — — Unused ON —

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

duration tSU. Refer to the thermal resistance charts in

the MOSFET data sheet to determine the junction tem-

perature rise during startup, and ensure that this does

not exceed the maximum junction temperature for worst-

case ambient conditions.

Circuit-Breaker Protection

As the channel is turned on and during normal operation,

two analog comparators are used to detect an overcur-

rent condition by sensing the voltage across an external

resistor connected between SENSE and MON. If the volt-

age across the sense resistor is less than the slow-trip

and fast-trip circuit-breaker thresholds, the GATE output

remains high. If either of the thresholds is exceeded due

to an overcurrent condition, the gate of the MOSFET

is pulled down to MON by an internal 500mA current

source.

The higher of the two comparator thresholds, the fast

trip, is set by an internal 8-bit DAC (see Table 7),

within one of three configurable full-scale current-sense

ranges: 25mV, 50mV, or 100mV (see Tables 6a and 6b).

The 8-bit fast-trip threshold DAC can be programmed

from 40% to 100% of the selected full-scale current-

sense range. The slow-trip threshold follows the fast-trip

threshold as one of four programmable ratios, set by the

ifast2slow register (see Tables 4a and 4b).

The fast-trip threshold is always higher than the slow-trip

threshold, and the fast-trip comparator responds very

quickly to protect the system against sudden, severe

overcurrent events. The slower response of the slow-

trip comparator varies depending upon the amount of

overdrive beyond the slow-trip threshold. If the overdrive

is small and short lived, the comparator will not shut

down the affected channel. As the overcurrent event

increases in magnitude, the response time of the slow-

trip comparator decreases. This scheme provides good

noise rejection and spurious overcurrent transients near

the slow-trip threshold, while aggressively protecting the

system against larger overcurrent events that occur as a

result of a load fault.

Figure 1. Channel On-Off Control Logic Functional Schematic

FORCE-ON

BIT

200ms DELAY,

THEN PULSE

CHANNEL

ENABLED

EN1 BIT

EN2 BIT

ANALOG SLOW TRIP

ANALOG FAST TRIP

UV/OV CRITICAL

PROT

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Setting Circuit-Breaker Thresholds

To select and set the device slow-trip and fast-trip com-

parator thresholds, use the following procedure:

1) Select one of four ratios between the fast-trip thresh-

old and the slow-trip threshold: 200%, 175%, 150%,

or 125%. A system that experiences brief but large

transient load currents should use a higher ratio,

whereas a system that operates continuously at high-

er average load currents might benefit from a smaller

ratio to ensure adequate protection. The ratio is set by

writing to the ifast2slow register. (The default setting

on power-up is 200%.)

2) Determine the slow-trip threshold VTH,ST based on the

anticipated maximum continuous load current during

normal operation, and the value of the current-sense

resistor. The slow-trip threshold should include some

margin (possibly 20%) above the maximum load cur-

rent to prevent spurious circuit-breaker shutdown and

to accommodate passive component tolerances:

VTH,ST = RSENSE x ILOAD,MAX x 120%

3) Calculate the necessary fast-trip threshold VTH,FT

based on the ratio set in step 1:

VTH,FT = VTH,ST x (ifast2slow ratio)

4) Select one of the three maximum current-sense

ranges: 25mV, 50mV, or 100mV. The current-sense

range is initially set upon power-up by the state of the

IRNG input, but can be altered at any time by writ-

ing to the status2 register. For maximum accuracy

and best measurement resolution, select the lowest

current-sense range that is larger than the VTH,FT

value calculated in step 3.

5) Program the fast-trip and slow-trip thresholds by writ-

ing an 8-bit value to the dac_fast register. This 8-bit

value is determined from the desired VTH,ST value

that was calculated in step 2, the threshold ratio from

step 1, and the current-sense range from step 4:

DAC = VTH,ST x 255 x (ifast2slow ratio)/

(IRNG current-sense range)

The device provides a great deal of system flexibil-

ity because the current-sense range, DAC setting, and

threshold ratio can be changed “on the fly” for systems

that must protect a wide range of interchangeable

load devices, or for systems that control the allocation

of power to smart loads. Table 5 shows the specified

ranges for the fast-trip and slow-trip thresholds for all

combinations of current-sense range and threshold ratio.

When an overcurrent event causes the device to shut

down the power channel, the open-drain FAULT output

alerts the system. Figure 2 shows the operation and fault-

management flowchart.

Table 4a. ifast2slow Register Format

Table 4b. Setting Fast-Trip to Slow-Trip Threshold Ratio

Description: Current threshold fast-to-slow setting bits

Resister Title: ifast2slow

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused FS1 FS0 0x0F

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

FS1 FS0 FAST-TRIP TO SLOW-TRIP RATIO (%)

0 0 125

0 1 150

1 0 175

1 1 200

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Table 5. Specified Current-Sense and Circuit-Breaker Threshold Ranges

Table 6a. IRNG Input Status Register Format

Table 6b. Setting Current-Sense Range

Table 7. dac_ch_ Register Format

IRNG

INPUT

DAC OUTPUT RANGE

(DEFAULT = FULL

SCALE) (mV)

FAST-TRIP

THRESHOLD RANGE

(mV)

GAIN (2 BIT) (VFAST/

VSLOW)

ifast2slow

(DEFAULT = 11)

SLOW-TRIP

THRESHOLD RANGE

(mV)

Low 10 to 25 10 to 25

00 (125%) 8.00 to 20.00

01 (150%) 6.67 to 16.67

10 (175%) 5.71 to 14.29

11 (200%) 5.00 to 12.50

High 20 to 50 20 to 50

00 (125%) 16.00 to 40.00

01 (150%) 13.33 to 33.33

10 (175%) 11.48 to 28.57

11 (200%) 10.00 to 25.00

Unconnected 40 to 100 40 to 100

00 (125%) 32.00 to 80.00

01 (150%) 26.67 to 66.67

10 (175%) 22.86 to 57.14

11 (200%) 20.00 to 50.00

Description: Fast-trip threshold maximum range-setting bits, from IRNG three-state input

Resister Title: status2

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused IRNG1 IRNG0 —

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

IRNG PIN STATE IRNG1 IRNG0 MAXIMUM CURRENT-SENSE SIGNAL (mV)

Low 1 0 25

High 0 1 50

Open 0 0 100

Description: Fast-comparator threshold DAC setting

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

DAC[7] DAC[6] DAC[5] DAC[4] DAC[3] DAC[2] DAC[1] DAC[0] 0xBF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Figure 2. Operation and Fault-Management Flowchart for Hot-Swap Channel

ARE 2 OR MORE OF 3

ENABLE SET?

READ, PROT, A0,

A1, HWEN, IRNG

INPUTS, CLEAR FLAGS

VIN > 2.7V

NO NO

CHANNEL ENABLED

START CIRCULAR BUFFER

ENABLE GATE PULLUP

MON > UV1

AND UV2?

ASSERT PG AFTER ADJUSTABLE DELAY YES

YESYES

NORMAL OPERATION

CIRCUIT-BREAKER

TRIP?

CONTINUOUSLY SAMPLE VOLTAGE AND

CURRENT, UPDATE MIN-MAX VALUES,

HANDLE I2C COMMUNICATIONS,

STORE SAMPLES TO CIRCULAR BUFFERS...

ARE 2 OR MORE OF

3 ENABLE SET?

UV, OV, OR OC

WARNING OR

CRITICAL

SET FAULT, CLEAR PG, AND SHUT DOWN

THE CHANNEL

BUFFER

STOP-DELAY

EXPIRED

STOP CIRCULAR BUFFER

YES

CLEAR PG AND

SHUT DOWN THE

CHANNEL

READ IRNG INPUT,

CLEAR FLAGS, CLEAR ALERT,

CLEAR FAULT

CHANNEL

ENABLED

ARE 2 OR MORE OF

3 ENABLE SET?

ARE 2 OR MORE OF

3 ENABLE SET?

YES

PROT INPUT = GND

SET ALERT, PG

PER PROT INPUT

YES

YES YES

YES

NORMAL

OPERATION

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Digital Current Monitoring

The current-sense signal is sampled by the internal

10-bit, 10ksps ADC, and the most recent results are

stored in registers for retrieval through the I2C interface.

The current conversion values are 10 bits wide, with the

8 high-order bits written to one 8-bit register and the 2

low-order bits written to the next-higher 8-bit register

address (Tables 8 and 9). This allows use of just the

high-order byte in applications where 10-bit precision is

not required. This split 8-bit/2-bit storage scheme is used

throughout the device for ADC conversion results and

digital comparator thresholds.

Once the PG output is asserted, the current-sense sam-

ples are continuously compared to the programmable

overcurrent warning register value. If the measured cur-

rent value exceeds the warning level, the ALERT output

is asserted. The device response to this digital com-

parator is not altered by the setting of the PROT input

(Tables 10 and 11).

Table 8. ADC Current-Conversion Results Register Format (High-Order Bits)

Table 9. ADC Current-Conversion Results Register Format (Low-Order Bits)

Table 10. Overcurrent Warning Threshold Register Format (High-Order Bits)

Table 11. Overcurrent Warning Threshold Register Format (Low-Order Bits)

Description: Most recent current-conversion result, high-order bits [9:2]

RESET

VALUE

R R R R R R R R

inew_9 inew_8 inew_7 inew_6 inew_5 inew_4 inew_3 inew_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Most recent current-conversion result, low-order bits [0:1]

RESET

VALUE

R R R R R R R R

— — — — — — inew_1 inew_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overcurrent warning threshold high-order bits [9:2]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

oi_9 oi_8 oi_7 oi_6 oi_5 oi_4 oi_3 oi_2 0xFF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overcurrent warning threshold low-order bits [1:0]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

— — — — — — oi_1 oi_0 0x03

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Minimum and Maximum Value Detection

for Current-Measurement Values

Current-sense measurement values from the ADC are

continuously compared with the contents of minimum-

and maximum-value registers, and if the most recent

measurement exceeds the stored maximum, or is less

than the stored minimum, the corresponding register

is updated with the new value. These “peak-detection”

registers are read/write accessible through the I2C inter-

face (Tables 12–15). The minimum-value registers are

reset to 0xFF and the maximum-value registers are reset

to 0x00. These reset values are loaded upon startup of

the channel or at any time as commanded by register

peak_log_rst (Table 35).

Table 12. ADC Minimum Current-Conversion Register Format (High-Order Bits)

Table 13. ADC Minimum Current-Conversion Register Format (Low-Order Bits)

Table 14. ADC Maximum Current-Conversion Register Format (High-Order Bits)

Table 15. ADC Maximum Current-Conversion Register Format (Low-Order Bits)

Description: Minimum current-conversion result high-order bits [9:2]

RESET

VALUE

R R R R R R R R

imin_9 imin_8 imin_7 imin_6 imin_5 imin_4 imin_3 imin_2 0xFF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Minimum current-conversion result low-order bits [1:0]

RESET

VALUE

R R R R R R R R

— — — — — — imin_1 imin_0 0x03

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Maximum current-conversion result high-order bits [9:2]

RESET

VALUE

R R R R R R R R

imax_9 imax_8 imax_7 imax_6 imax_5 imax_4 imax_3 imax_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Maximum current-conversion result low-order bits [1:0]

RESET

VALUE

R R R R R R R R

— — — — — — imax_1 imax_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Digital Voltage Monitoring and Power-Good

Output

The voltage at the load (MON input) is sampled by the

internal ADC. The MON full-scale voltage can be set to

16V, 8V, 4V, or 2V by writing to register mon_range. The

default range is 16V (Tables 16 and 17).

The most recent voltage-conversion results can be read

from the adc_mon_msb and adc_mon_lsb registers (see

Tables 18 and 19).

Digital Undervoltage- and Overvoltage-

Detection Thresholds

The most recent voltage values are continuously com-

pared to four programmable limits, comprising two

undervoltage (UV) levels (see Tables 20 to 23) and two

overvoltage (OV) levels (see Tables 24 to 27).

If PG is asserted and the voltage is outside the warning

limits, the ALERT output is asserted low. Depending on

the status of the prot[] bits in register status1[7:6], the

Table 16. ADC Voltage Monitor Settings Register Format

Table 17. ADC Full-Scale Voltage Setting

Table 18. ADC Voltage-Conversion Result Register Format (High-Order Bits)

Table 19. ADC Voltage-Conversion Result Register Format (Low-Order Bits)

Description: ADC voltage monitor full-scale range settings (for MON input)

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

— — — — Unused Unused MON_rng1 MON_rng0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MON_rng1 MON_rng0 ADC FULL-SCALE VOLTAGE (V)

0 0 16

0 1 8

1 0 4

1 1 2

Description: Most recent voltage-conversion result, high-order bits [9:2]

RESET

VALUE

R R R R R R R R

vnew_9 vnew_8 vnew_7 vnew_6 vnew_5 vnew_4 vnew_3 vnew_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Most recent voltage-conversion result, low-order bits [1:0]

RESET

VALUE

R R R R R R R R

— — — — — — vnew_1 vnew_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

device can also deassert the PG output or turn off the

external MOSFET when the voltage is outside the critical

limits (see Figure 3). Table 28 shows the behavior for the

three possible states of the PROT input. Note that the

PROT input does not affect the device response to the

UV or OV warning digital comparators; it only determines

the system response to the critical digital comparators

(see Tables 3a, 3b, and 28).

In a typical application, the UV1 and OV1 thresholds

would be set closer to the nominal output voltage, and

the UV2 and OV2 thresholds would be set further from

nominal. This provides a “progressive” response to a

voltage excursion. However, the thresholds can be con-

figured in any arrangement or combination as desired to

suit a given application.

Figure 3. Graphical Representation of Typical UV and OV Thresholds Configuration

Table 20. Undervoltage Warning Threshold Register Format (High-Order Bits)

Table 21. Undervoltage Warning Threshold Register Format (Low-Order Bits)

OV2 CRITICAL THRESHOLD

UV2 CRITICAL THRESHOLD

UV1 WARNING THRESHOLD

OV1 WARNING THRESHOLD

NORMAL RANGE

VMON

Description: Undervoltage warning threshold high-order bits [9:2]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

uv1_9 uv1_8 uv1_7 uv1_6 uv1_5 uv1_4 uv1_3 uv1_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Undervoltage warning threshold low-order bits [1:0]

RESET

VALUE

R R R R R R R/W R/W

— — — — — — uv1_1 uv1_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Table 22. Undervoltage Critical Threshold Register Format (High-Order Bits)

Table 23. Undervoltage Critical Threshold Register Format (Low-Order Bits)

Table 24. Overvoltage Warning Threshold Register Format (High-Order Bits)

Table 25. Overvoltage Warning Threshold Register Format (Low-Order Bits)

Table 26. Overvoltage Critical Threshold Register Format (High-Order Bits)

Description: Undervoltage critical threshold high-order bits [9:2]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

uv2_9 uv2_8 uv2_7 uv2_6 uv2_5 uv2_4 uv2_3 uv2_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Undervoltage critical threshold low-order bits [1:0]

RESET

VALUE

R R R R R R R/W R/W

— — — — — — uv2_1 uv2_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overvoltage warning threshold high-order bits [9:2]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

ov1_9 ov1_8 ov1_7 ov1_6 ov1_5 ov1_4 ov1_3 ov1_2 0xFF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overvoltage warning threshold low-order bits [1:0]

RESET

VALUE

R R R R R R R/W R/W

— — — — — — ov1_1 ov1_0 0x03

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overvoltage critical threshold high-order bits [9:2]

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

ov2_9 ov2_8 ov2_7 ov2_6 ov2_5 ov2_4 ov2_3 ov2_2 0xFF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Power-Good Detection and PG Output

The PG output is asserted when the voltage at MON is

between the undervoltage and overvoltage critical limits.

The status of the power-good signal is maintained in

a power-good condition, regardless of the POL setting,

which only affects the PG output pin polarity. The open-

drain PG output can be configured for active-high or

active-low status indication by the state of the POL input

(see Table 29).

The POL input sets the value of status3[5], which is a

read-only bit; the state of the POL input can be changed

at any time during operation and the polarity of the PG

output changes accordingly.

The assertion of the PG output is delayed by a user-

selectable time delay of 50ms, 100ms, 200ms, or 400ms

(see Tables 30a and 30b).

Table 27. Overvoltage Critical Threshold Register Format (Low-Order Bits)

Table 28. PROT Input and prot[] Bits

Table 29. status3 Register Format

Table 30a. Power-Good Assertion Delay-Time Register Format

Table 30b. Power-Good Assertion Delay

Description: Overvoltage critical threshold low-order bits [1:0]

RESET

VALUE

R R R R R R/W R/W R/W

— — — — — — ov2_1 ov2_0 0x03

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

PROT INPUT

STATE prot[1] prot[0] UV/OV WARNING

ACTION UV/OV CRITICAL ACTION

Low 0 0 Assert ALERT Assert ALERT, clear PG, shut down channel

High 0 1 Assert ALERT Assert ALERT, clear PG

Unconnected 1 0 Assert ALERT Assert ALERT

Description: Power-good status register: POL, ALERT, and power-good bits

RESET

VALUE

R R R R/W R R R R

— — POL ALERT — — Unused pg[0] —

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Power-good assertion delay-time register

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused pgdly1 pgdly0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

pgdly1 pgdly0 PG ASSERTION DELAY (ms)

0 0 50

0 1 100

1 0 200

1 1 400

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Minimum and Maximum Value Detection

for Voltage-Measurement Values

All voltage-measurement values are compared with the

contents of minimum- and maximum-value registers,

and if the most recent measurement exceeds the stored

maximum or is less than the stored minimum, the corre-

sponding register is updated with the new value. These

peak-detection registers are read accessible through the

I2C interface (see Tables 31 to 34). The minimum-value

registers are reset to 0xFF, and the maximum-value reg-

isters are reset to 0x00. These reset values are loaded

upon startup or at any time as commanded by register

peak_log_rst (see Table 35).

Table 31. ADC Minimum Voltage Conversion Register Format (High-Order Bits)

Table 32. ADC Minimum Voltage-Conversion Register Format (Low-Order Bits)

Table 33. ADC Maximum Voltage-Conversion Register Format (High-Order Bits)

Table 34. ADC Maximum Voltage-Conversion Register Format (Low-Order Bits)

Description: Minimum voltage conversion result, high-order bits [9:2]

RESET

VALUE

R R R R R R R R

vmin_9 vmin_8 vmin_7 vmin_6 vmin_5 vmin_4 vmin_3 vmin_2 0xFF

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Minimum voltage-conversion result, low-order bits [1:0]

RESET

VALUE

R R R R R R R R

— — — — — — vmin_1 vmin_0 0x03

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Maximum voltage-conversion result, high-order bits [9:2]

RESET

VALUE

R R R R R R R R

vmax_9 vmax_8 vmax_7 vmax_6 vmax_5 vmax_4 vmax_3 vmax_2 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Maximum voltage-conversion result, low-order bits [1:0]

RESET

VALUE

R R R R R R R R

— — — — — — vmax_1 vmax_0 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Using the Voltage and Current Peak-

Detection Registers

The voltage and current minimum- and maximum-value

records in register locations 0x08 through 0x17 can be

reset by writing a 1 to the appropriate location in register

peak_log_rst (see Table 35). The minimum-value regis-

ters are reset to 0xFF, and the maximum-value registers

are reset to 0x000.

As long as a bit in peak_log_rst is 1, the corresponding

peak-detection registers are disabled and are “cleared”

to their power-up reset values. The voltage and current

minimum- and maximum-detection register contents can

be “held” by setting bits in register peak_log_hold (see

Table 36). Writing a 1 to a location in peak_log_hold

locks the register contents for the corresponding signal

and stops the min/max detection and logging; writing a

0 enables the detection and logging. Note that the peak-

detection registers cannot be cleared while they are held

by register peak_log_hold.

The combination of these two control registers allows the

user to monitor voltage and current peak-to-peak values

during a particular time period.

Table 35. Peak-Detection Reset-Control Register Format

Table 36. Peak-Detection Hold-Control Register Format

Description: Reset control bits for peak-detection registers

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused v_rst i_rst 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Hold control bits for peak-detection registers

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused Ch0_v_hld Ch0_i_hld 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Deglitching of Digital Comparators

The five digital comparators (undervoltage/overvoltage

warning and critical, overcurrent warning) all have a

user-selectable deglitching feature that requires two

consecutive positive compares before the device takes

action as determined by the particular compare and the

setting of the PROT input.

The deglitching functions are enabled or disabled by

registers dgl_i, dgl_uv, and dgl_ov (Tables 37, 38, and

39). Writing a 1 to the appropriate bit location in these

registers enables the deglitch function for the corre-

sponding digital comparator.

Circular Buffer

The device features two 10-bit “circular buffers” (in vola-

tile memory) that contain a history of the 50 most-recent

voltage and current digital-conversion results. These cir-

cular buffers can be read back through the I2C interface.

The recording of new data to the buffer for a given signal

is stopped under any of the following conditions:

• Thehot-swapchannelisshutdownbecauseofafault

condition.

• A read of the circular buffer base address is per-

formed through the I2C interface.

• Thehot-swapchannelisturnedoffbyacombination

of the EN1, EN2, or ON signals.

The buffers allow the user to recall the voltage and cur-

rent waveforms for analysis and troubleshooting. The

buffer contents are accessed through the I2C interface

at two fixed addresses in the device register address

space (see Table 40).

Each buffer can also be stopped under user control by

Table 37. OI Warning Comparators Deglitch Enable Register Format

Table 38. UV Warning and Critical Comparators Deglitch Enable Register Format

Table 39. OV Warning and Critical Comparators Deglitch Enable Register Format

Description: Deglitch enable register for overcurrent warning digital comparators

RESET

VALUE

R R R R R R R/W R/W

— — — — — — Unused dgl_i 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Deglitch enable register for undervoltage warning and critical digital comparators

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused dgl_uv2 dgl_uv1 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Deglitch enable register for overvoltage warning and critical digital comparators

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused dgl_ov2 dgl_ov1 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

The contents of a buffer can be retrieved as a block read

of either fifty 10-bit values (spanning 2 bytes each) or of

50 high-order bytes, depending on the per-signal bit set-

tings of register cbufrd_hibyonly (see Table 42).

If the circular buffer contents are retrieved as 10-bit

data, the first byte read-out is the high-order 8 bits of the

10-bit sample, and the second byte read-out contains

the 2 least-significant bits (LSBs) of the sample. This is

repeated for each of the 50 samples in the buffer. Thus,

2 bytes must be read for each 10-bit sample retrieved.

Conversely, if the buffer contents are retrieved as 8-bit

data, then each byte read-out contains the 8 MSBs of

each successive sample. It is important to remember

that in 10-bit mode, 100 bytes must be read to extract the

entire buffer contents, but in 8-bit mode, only 50 bytes

must be read.

The circular buffer system has a user-programmable

“stop delay” that specifies a certain number of sample

cycles to continue recording to the buffer after a shut-

down occurs. This delay value is stored in register

cbuf_dly_stop[5:0] (see Table 43).

The default (reset) value of the buffer stop delay is

25 samples, which means that an equal number of

samples are stored in the buffer preceding and follow-

ing the moment of the shutdown event. The buffer stop

delay is analogous to an oscilloscope trigger delay

because it allows the device to record what happened

both immediately before and after a shutdown. In other

words, when the contents of a circular buffer are read

out of the device, the shutdown event is by default

located in the middle of the recorded data. The balance

of data before and after an event can be altered by writ-

ing a different value (between 0 and 50) to the buffer

stop-delay register.

Latched-Off Fault Management

In the event of an overcurrent, undervoltage, or overvolt-

age condition that results in the shutdown of the hot-

swap channel, the device remains latched off.

To restart the latched-off channel, the user must either

cycle power to the IN input, or toggle the ON pin, EN1

bit, or the EN2 bit.

Table 40. Circular Buffer Read Addresses

Table 41. Circular Buffer Control Register Format

Table 42. Circular Buffer Resolution Register Format

ADDRESS NAME DESCRIPTION

0x46 cbuf_ba_v Base address for voltage buffer block read

0x47 cbuf_ba_i Base address for current buffer block read

Description: Circular buffer run-stop control register (per-buffer control: 1 = run, 0 = stop)

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused Ch0_i_run Ch0_v_run 0x0F

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Circular buffer read-out resolution: high-order byte only, or 8-2 split 10-bit data

(per-buffer control: 1 = high-order byte output, 0 = full-resolution 10-bit output)

RESET

VALUE

R R R R R/W R/W R/W R/W

— — — — Unused Unused i_res v_res 0x0F

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Force-On Function

When the force-on bit is set to 1 in register foset[0] (see

Table 44), the channel is enabled regardless of the ON

pin voltage or the EN1 and EN2 bits in register chxen. In

forced-on operation, all functions operate normally with

the notable exception that the channel does not shut

down due to any fault conditions that may arise.

There is a force-on key register fokey that must be set to

0xA5 in order for the force-on function to become active

(see Table 45). If this register contains any value other

than 0xA5, writing 1 to the force-on bits in register foset

has no effect. This provides protection against acciden-

tal force-on operation that might otherwise be caused by

an erroneous I2C write.

Fault Logging and Indications

The device provides detailed information about any fault

conditions that have occurred. The FAULT output spe-

cifically indicates a circuit-breaker shutdown event, while

the ALERT output is asserted whenever a problem has

occurred that requires attention or interaction.

Table 43. Circular Buffer Stop-Delay Register Format

Table 44. Force-On Control Register Format

Table 45. Force-On Key Register Format

Description: Circular buffer stop delay: any integer number between 0 and 50 samples that are to be recorded to a

buffer after a shutdown event, before the buffer stops storing new data

RESET

VALUE

R R R/W R/W R/W R/W R/W R/W

0 0 Stop_dly[5] Stop_dly[4] Stop_dly[3] Stop_dly[2] Stop_dly[1] Stop_dly[0] 0x19

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Force-on control register

RESET

VALUE

R R R R R R R/W R/W

0 0 0 0 0 0 Unused fo 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Force-on key register (must contain 0xA5 to unlock force-on feature)

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

fokey[7] fokey[6] fokey[5] fokey[4] fokey[3] fokey[2] fokey[1] fokey[0] 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Fault Dependency

If a fault event occurs (digital UV warning/critical, digital

OV warning/critical, or digital overcurrent warning), the

fault is logged by setting a corresponding bit in registers

fault0, fault1, or fault2 (see Tables 46, 47, and 48).

Likewise, circuit-breaker shutdown events are logged in

IFAULTS indicates the overcurrent status from slow com-

parator. IFAULTF indicates overcurrent status from fast

comparator. The status of FAULT reflects the OR opera-

tion of IFAULTS and IFAULTF.

These fault register bits latch upon a fault condition, and

must be reset manually by restarting as described in the

Latched-Off Fault Management section.

Table 46. Undervoltage Status Register Format

Table 47. Overvoltage Status Register Format

Table 48. Overcurrent Warning Status Register Format

Table 49. Circuit-Breaker Event Logging Register Format

Description: Undervoltage digital-compare status register (warning [0] and critical [4] undervoltage event-

detection status)

RESET

VALUE

R R R/C R/C R R R/C R/C

— — Unused uv1 — — Unused uv1 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overvoltage digital-compare status register (warning [0] and critical [4] overvoltage event-detection

status)

RESET

VALUE

R R R/C R/C R R R/C R/C

— — Unused ov2 — — Unused ov1 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Overcurrent digital-compare status register (overcurrent warning event-detection status)

RESET

VALUE

R R R R R R R/C R/C

— — — — — — Unused oi 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: Circuit-breaker slow- and fast-trip event logging

RESET

VALUE

R R R R R R R R

— — Unused IFAULTS — — Unused IFAULTF 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

FAULT Output

When an overcurrent event (fast trip or slow trip) causes

the device to shut down the hot-swap channel, an open-

drain FAULT output is asserted low. Note that the FAULT

output is not asserted for shutdowns caused by critical

undervoltage or overvoltage events.

The FAULT output is cleared when the channel is dis-

abled by pulling ON low or by clearing the bits in register

chxen.

ALERT Output

ALERT is an open-drain output that is asserted low any

time that a fault or other condition requiring attention has

occurred. The state of the ALERT output is also indicated

by status3[4].

The ALERT output is the logical NOR of registers 0x31,

0x35, 0x36, and 0x37, so when the ALERT output goes

low, the system microcontroller should query these reg-

isters through the I2C interface to determine the cause of

the ALERT assertion.

LED Set Registers

The device has four open-drain LED drivers/user-pro-

grammable GPIOs. When programmed as LED drivers,

each driver can sink up to 25mA of current. Table 50

shows the register that enables the drivers as either LED

drivers or GPIOs.

When any of the LED_ Set bit in the register is set to 1,

the corresponding open-drain LED driver is turned off.

The LED_Flash bits enable each corresponding LED

driver to flash on and off at 1Hz frequency regardless of

the condition of the corresponding LED_ Set bit.

Bits 7–4 in Table 51 set the LED flashing drivers to be

either in-phase or out-of-phase with the internal 1Hz

clock. Bits 3–0 enable the 4FA pullup current to the cor-

responding output.

Table 52 shows the LED state register. The LED state reg-

ister is a read-only register. When the LEDs are disabled,

the pins are configured as GPIOs. Applying an external

voltage below 0.4V sets the GPIOs low and, applying an

external voltage above 1.4V, sets the GPIOs high.

Table 50. LED_Flash/GPIO Enable Register

Table 51. LED Phase/Weak Pullup Enable Register

Description: LED_ flash/GPIO enable register

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

LED4

Flash

LED3

Flash

LED2

Flash LED1 Flash LED4 Set LED3 Set LED2 Set LED1 Set 0x0F

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

Description: LED phase/weak pullup enable

RESET

VALUE

R/W R/W R/W R/W R/W R/W R/W R/W

LED4

Phase

LED3

Phase

LED2

Phase

LED1

Phase

LED4 Weak

LED3 Weak

LED2 Weak

LED1 Weak

PU 0x00

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

I2C Serial Interface

The device features an I2C-compatible serial interface

consisting of a serial data line (SDA) and a serial clock

line (SCL). SDA and SCL allow bidirectional communica-

tion between the device and the master device at clock

rates from 100kHz to 400kHz. The I2C bus can have

several devices (e.g., more than one device, or other I2C

devices in addition to the device) attached simultane-

ously. The A0 and A1 inputs set one of nine possible I2C

addresses (see Table 53).

The 2-wire communication is fully compatible with exist-

ing 2-wire serial interface systems; Figure 4 shows

the interface timing diagram. The device is a transmit/

receive slave-only device, relying upon a master device

to generate a clock signal. The master device (typically

a microcontroller) initiates data transfer on the bus and

generates SCL to permit that transfer.

A master device communicates to the device by trans-

mitting the proper address followed by command and/

or data words. Each transmit sequence is framed by

a START (S) or Repeated START (SR) condition and a

STOP (P) condition. Each word transmitted over the bus

is 8 bits long and is always followed by an acknowledge

pulse.

SCL is a logic input, while SDA is a logic input/open-

drain output. SCL and SDA both require external pullup

resistors to generate the logic-high voltage. Use 4.7kI

for most applications.

Table 52. LED State Register

Figure 4. Serial-Interface Timing Details

STOP

CONDITION

REPEATED START

CONDITION

START

CONDITION

tHIGH

tLOW

tRtF

tSU:DAT tSU:STA tSU:STO

tHD:STA

tBUF

tHD:STA

tHD:DAT

SCL

SDA

START

CONDITION

Description: LED state register

RESET

VALUE

R R R R R R R R

— — — — LED4

Voltage

LED3

Voltage

LED2

Voltage

LED1

Voltage —

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 —

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Bit Transfer

Each clock pulse transfers 1 data bit. The data on SDA

must remain stable while SCL is high (see Figure 5); oth-

erwise, the device registers a START or STOP condition

(see Figure 6) from the master. SDA and SCL idle high

when the bus is not busy.

START and STOP Conditions

Both SCL and SDA idle high when the bus is not busy.

A master device signals the beginning of a transmission

with a START condition (see Figure 3) by transitioning

SDA from high to low while SCL is high. The master

device issues a STOP condition (see Figure 6) by transi-

tioning SDA from low to high while SCL is high. A STOP

condition frees the bus for another transmission. The bus

remains active if a Repeated START condition is gener-

ated, such as in the block read protocol (see Figure 7).

Early STOP Conditions

The device recognizes a STOP condition at any point

during transmission except if a STOP condition occurs in

the same high pulse as a START condition. This condi-

tion is not a legal I2C format. At least one clock pulse

must separate any START and STOP condition.

Repeated START Conditions

A Repeated START (SR) condition may indicate a change

of data direction on the bus. Such a change occurs when

a command word is required to initiate a read operation

(see Figure 4). SR may also be used when the bus mas-

ter is writing to several I2C devices and does not want to

relinquish control of the bus. The device serial interface

supports continuous write operations with or without an

SR condition separating them. Continuous read opera-

tions require SR conditions because of the change in

direction of data flow.

Table 53. Device Slave Address Settings

Figure 5. Bit Transfer Figure 6. START and STOP Conditions

DATA LINE STABLE,

DATA VALID

SDA

SCL

CHANGE OF

DATA ALLOWED

START

CONDITION

SDA

SCL

STOP

CONDITION

ADDRESS INPUT

STATE I2C ADDRESS BITS

A1 A0 ADDR 7 ADDR 6 ADDR 5 ADDR 4 ADDR 3 ADDR 2 ADDR 1 ADDR 0

Low Low 0 1 1 1 0 1 0 R/W

Low High 0 1 1 1 0 0 1 R/W

Low Open 0 1 1 1 0 0 0 R/W

High Low 0 1 1 0 1 1 0 R/W

High High 0 1 1 0 1 0 1 R/W

High Open 0 1 1 0 1 0 0 R/W

Open Low 0 1 1 0 0 1 0 R/W

Open High 0 1 1 0 0 0 1 R/W

Open Open 0 1 1 0 0 0 0 R/W

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Figure 7. SMBus/I2C Protocols

WRITE BYTE FORMAT

ADDRESS

7 BITS

SEND BYTE FORMAT

RECEIVE BYTE FORMAT

ACK

DATA

8 BITS

ACK P

DATA BYTE–PRESETS THE

INTERNAL ADDRESS POINTER.

DATA BYTE–READS DATA FROM

THE REGISTER COMMANDED BY

THE LAST READ BYTE OR WRITE

BYTE TRANSMISSION. ALSO

DEPENDENT ON A SEND BYTE.

WRITE WORD FORMAT

S ADDRESS WR ACK ACK ACK ACKCOMMAND DATA DATA P

7 BITS 8 BITS 8 BITS 8 BITS

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

COMMAND BYTE–

MSB OF THE

EEPROM

WRITTEN.

DATA BYTE–FIRST BYTE IS THE LSB OF

THE EEPROM ADDRESS. SECOND

BYTE IS THE ACTUAL DATA.

BLOCK WRITE FORMAT

S ADDRESS WR ACK COMMAND ACK BYTE

COUNT = N ACK DATA BYTE

1ACK DATA BYTE

... ACK DATA BYTE

NACK P

7 BITS 8 BITS 8 BITS 8 BITS 8 BITS

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

COMMAND BYTE–

PREPARES DEVICE

FOR BLOCK

OPERATION.

DATA BYTE–DATA GOES INTO THE REGISTER SET BY THE

COMMAND BYTE.

BLOCK READ FORMAT

S ADDRESS WR ACK COMMAND ACK SR ADDRESS WR ACK

8 BITS

BYTE

COUNT = 16 ACK DATA BYTE

1ACK DATA BYTE

... ACK DATA BYTE

NACK P

7 BITS 8 BITS 7 BITS 10h 8 BITS8 BITS 8 BITS

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

COMMAND BYTE–

PREPARES DEVICE

FOR BLOCK

OPERATION.

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

DATA BYTE–DATA GOES INTO THE REGISTER SET BY THE

COMMAND BYTE.

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

Sr = REPEATED START CONDITION

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

S ADDRESS WR ACK COMMAND ACK DATA ACK P

7 BITS 8 BITS 8 BITS

SLAVE ADDRESS–

EQUIVALENT TO CHIP-

SELECT LINE OF A

3-WIRE INTERFACE.

COMMAND BYTE–

SELECTS REGISTER

BEING WRITTEN.

DATA BYTE–DATA GOES INTO THE

BYTE IF THE COMMAND IS BELOW

50h. IF THE COMMAND IS 80h,

81h, or 82h, THE DATA BYTE

PRESETS THE LSB OF AN EEPROM

ADDRESS.

1 0

0 0

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Acknowledge

The acknowledge bit (ACK) is the 9th bit attached to any

8-bit data word. The receiving device always generates

an ACK. The device generates an ACK when receiving

an address or data by pulling SDA low during the 9th

clock period (see Figure 8). When transmitting data,

such as when the master device reads data back from

the device, the device waits for the master device to

generate an ACK. Monitoring ACK allows for detection

of unsuccessful data transfers. An unsuccessful data

transfer occurs if the receiving device is busy or if a sys-

tem fault has occurred. In the event of an unsuccessful

data transfer, the bus master should reattempt commu-

nication at a later time. The device generates a NACK

after the slave address during a software reboot or when

receiving an illegal memory address.

Send Byte

The send byte protocol allows the master device to send

1 byte of data to the slave device (see Figure 7). The

send byte presets a register pointer address for a sub-

sequent read or write. The slave sends a NACK instead

of an ACK if the master tries to send an address that is

not allowed. If the master sends a STOP condition, the

internal address pointer does not change. The send byte

procedure follows:

1) The master sends a START condition.

2) The master sends the 7-bit slave address and a write

bit (low).

3) The addressed slave asserts an ACK on SDA.

4) The master sends an 8-bit data byte.

5) The addressed slave asserts an ACK on SDA.

6) The master sends a STOP condition.

Write Byte

The write byte/word protocol allows the master device

to write a single byte in the register bank or to write to a

series of sequential register addresses. The write byte

procedure follows:

1) The master sends a START condition.

2) The master sends the 7-bit slave address and a write

bit (low).

3) The addressed slave asserts an ACK on SDA.

4) The master sends an 8-bit command code.

5) The addressed slave asserts an ACK on SDA.

6) The master sends an 8-bit data byte.

7) The addressed slave asserts an ACK on SDA.

8) The addressed slave increments its internal address

pointer.

9) The master sends a STOP condition or repeats steps

6, 7, and 8.

To write a single byte to the register bank, only the 8-bit

command code and a single 8-bit data byte are sent.

The data byte is written to the register bank if the com-

mand code is valid.

Figure 8. Acknowledge

SCL 1

28 9

SDA BY

TRANSMITTER

SDA BY

RECEIVER

START

CONDITION CLOCK PULSE FOR ACKNOWLEDGE

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

The slave generates a NACK at step 5 if the command

code is invalid. The command code must be in the 0x00

to 0x45 range. The internal address pointer returns

to 0x00 after incrementing from the highest register

address.

Receive Byte

The receive-byte protocol allows the master device to

read the register content of the device (see Figure 7).

The EEPROM or register address must be preset with a

send-byte protocol first. Once the read is complete, the

internal pointer increases by one. Repeating the receive

byte protocol reads the contents of the next address.

The receive-byte procedure follows:

1) The master sends a START condition.

2) The master sends the 7-bit slave address and a read

bit (high).

3) The addressed slave asserts an ACK on SDA.

4) The slave sends 8 data bits.

5) The slave increments its internal address pointer.

6) The master asserts an ACK on SDA and repeats

steps 4, 5 or asserts a NACK and generates a STOP

condition.

The internal address pointer returns to 0x00 after incre-

menting from the highest register address.

Address Pointers

Use the send-byte protocol to set the register address

pointers before read and write operations. For the con-

figuration registers, valid address pointers range from

0x00 to 0x45, and the circular buffer addresses are 0x46

to 0x49. Register addresses outside this range result in

a NACK being issued from the device.

Circular Buffer Read

The circular buffer read operation is similar to the

receive-byte operation. The read operation is triggered

after any one of the circular buffer base addresses is

loaded. During a circular buffer read, although all is

transparent from the external world, internally the autoin-

crement function in the I2C controller is disabled. Thus,

it is possible to read one of the circular buffer blocks

with a burst read without changing the virtual internal

address corresponding to the base address. Once the

master issues a NACK, the circular reading stops, and

the default functions of the I2C slave bus controller are

restored.

In 8-bit read mode, every I2C read operation shifts out

a single sample from the circular buffer. In 10-bit mode,

two subsequent I2C read operations shift out a single

10-bit sample from the circular buffer, with the high-order

byte read first, followed by a byte containing the right-

shifted 2 least-significant bits. Once the master issues a

NACK, the read circular buffer operation terminates and

normal I2C operation returns.

The data in the circular buffers is read back with the

next-to-oldest sample first, followed by progressively

more recent samples until the most recent sample is

retrieved, followed finally by the oldest sample (see

Table 54).

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land pat terns,

go to www.maxim-ic.com/packages. Note that a “+”, “#”, or

“-” in the package code indicates RoHS status only. Package

drawings may show a different suf fix character, but the drawing

pertains to the package regardless of RoHS status.

Table 54. Circular Buffer Readout Sequence

READ-OUT ORDER 1ST OUT 2ND OUT … 48TH OUT 49TH OUT 50TH OUT

Chronological Number 1 2 … 48 49 0

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

32 TQFN-EP T3255+4 21-0140 90-0012

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.

Maxim reserves the right to change the circuitry and specifications without notice at any time.

38 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

MAX5978

0 to 16V, Hot-Swap Controller with 10-Bit

Current, Voltage Monitor, and 4 LED Drivers

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 7/10 Initial release —

Mouser Electronics

Authorized Distributor

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