MAX1558ETB - Maxim Integrated Products, Inc.

General Description

The MAX1558/MAX1558H are dual, current-limited

switches with autoreset for USB applications. Autoreset

latches the switch off if it is shorted for more than 20ms,

saving system power. The shorted output is then tested

to determine when the short is removed to automatically

restart the channel. Each channel delivers up to 1.2A

and meets all IEC specifications for USB ports. Low

quiescent supply current (45µA) and standby current

(3µA) conserve battery power in portable applications.

The MAX1558/MAX1558H safety features ensure that the

USB port is protected. Built-in thermal-overload protection

limits power dissipation and junction temperature.

Accurate, programmable current-limiting circuitry pro-

tects the input supply against both overload and short-cir-

cuit conditions. 20ms fault blanking enables the circuit to

ignore transient faults, such as those caused when hot

swapping a capacitive load, preventing false alarms to

the host system. The MAX1558/MAX1558H also feature

reverse-current protection circuitry to block current flow

from the output to the input when the switches are off.

The MAX1558/MAX1558H are available in space-sav-

ing 3mm x 3mm, 10-pin TDFN packages. The MAX1558

is enabled with an active-low signal, and the

MAX1558H is enabled with an active-high signal.

Applications

USB Ports and Hubs

Notebook Computers and Desktops

PDAs and Palmtop Computers

Docking Stations

Features

♦55mΩSwitch Resistance

♦Tiny 10-Pin, 3mm x 3mm TDFN Package

♦14% Accurate Current Limit

♦Autorestart when Fault is Removed

♦Programmable Current Up to 1.2A

♦Thermal-Overload Protection

♦Built-In 20ms Fault Blanking

♦Compliant to All USB Specifications

♦2.7V to 5.5V Supply Range

♦Independent-Output Fault Indicators

♦Block Reverse Current when Disabled

♦15kV ESD Protection (with Capacitor)

♦UL Listing Pending

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3128; Rev 0; 6/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART TEMP RANGE PIN-

PACKAGE

TOP

MARK

MAX1558ETB -40°C to +85°C10 TDFN

(3mm x 3mm) AAR

MAX1558HETB -40°C to +85°C10 TDFN

(3mm x 3mm) AAS

MAX1558

INPUT

2.7V TO 5.5V

INA

INB

ISET

FLTA

FLTB

ONA

ONB

ONA

ONB

OUTA

OUTB

GND

USB

PORT A

USB

PORT B

Typical Operating Circuit

TDFN

3mm x 3mm

TOP VIEW

MAX1558

(MAX1558H)

ISET

INA

INB

ONA (ONA)

ONB (ONB)

OUTA

GND

OUTB

FLTA

FLTB

Pin Configuration

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩto GND, TA= 0°C to +85°C,

unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)

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_, ON_, OUT_, ISET, FLT_ to GND........................-0.3V to +6V

IN_ to OUT_ (when disabled) (Note 1) ........................-6V to +6V

IN_ to OUT_ (when enabled) (Note 2)............-1.6A to +1.6ARMS

FLT_ Sink Current................................................................20mA

Continuous Power Dissipation (TA= +70°C)

10-Pin TDFN 3mm x 3mm

(derate 24.4mW/°C above +70°C).............................1952mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+160°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage Range 2.75 5.50 V

VIN_ = 5V, TA = +25°C5575

VIN_ = 3.3V, TA = +25°C64Switch On-Resistance RON

VIN_ = 4.4V, TA = 0°C to +85°C 105

mΩ

Standby Supply Current Both switches disabled 3 6 µA

Quiescent Supply Current Both switches enabled 45 75 µA

VOUTA = VOUTB = 0V 0.03 10

OUT_ Off-Leakage Current Switches disabled VOUTA = VOUTB = 5V 0.03 µA

Reverse Leakage Current VIN_ = 0V, VOUTA = VOUTB = 5V, both

switches disabled 0.03 µA

Undervoltage-Lockout Threshold VUVLO Rising edge, 3% hysteresis 2.3 2.5 2.7 V

Continuous Load Current RISET = 26kΩ1.2 A

RISET = 26kΩ1.20 1.4 1.60

RISET = 39kΩ0.80 0.925 1.05Current-Limit Threshold VIN_ - VOUT_ =

0.5V

RISET = 60kΩ0.50 0.6 0.70

RISET = 26kΩ1.45 2.0 2.60

RISET = 39kΩ1.40Peak Short-Circuit Current Limit ISHORT VOUT_ = 0V

(IOUT_ pulsing) RISET = 60kΩ0.90

(

PEAK

)

RISET = 26kΩ0.55

RISET = 39kΩ0.37

RMS Short-Circuit Current Limit ISHORT VOUT_ = 0V

(IOUT_ pulsing) RISET = 60kΩ0.23

ARMS

Short-Circuit Continuous Current-

Limit Transition Threshold (Note 4) 1 V

Fault-Blanking Timeout Period From ILIMIT condition to 50% of V FLT_ 82040ms

Turn-On Delay tON

ROUT_ = 10Ω, COUT_ = 1µF, does not

include rise time (from ON asserted to

VOUT_ = 10% VIN_)

0.5 1.4 4.0 ms

Note 1: Reverse current (current from OUT_ to IN_) is blocked when disabled.

Note 2: Forward current (current from IN_ to OUT_) is internally limited. Reverse current, from OUT_ to IN_, is not limited when the

device is enabled and must be kept below 1.5ARMS to prevent permanent device damage. When the MAX1558/MAX1558H

are disabled, the switch turns off and reverse current is internally blocked.

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩto GND, TA= 0°C to +85°C,

unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Output Rise Time tRISE COUT_ = 1µF, ROUT_ = 10Ω, (from 10% to

90% of VOUT_)4ms

Turn-Off Delay from ON tOFF

ROUT_ = 10Ω, COUT_ = 1µF, does not

include rise time (from ON deasserted to

VOUT_ = 90% VIN_)

100 1000 µs

Output Fall Time tFALL COUT_ = 1µF, ROUT_ = 10Ω (from 90% to

10% of VOUT_)3ms

Thermal-Shutdown Threshold 10°C hysteresis +160 °C

VIN_ = 2.7V to 4.0V 1.6

ONA/ONB Logic Input High

Voltage VIH VIN_ = 4.0V to 5.5V 2.0 V

VIN_ = 2.7V to 4.0V 0.6

ONA/ONB Logic Input Low

Voltage VIL VIN_ = 4.0V to 5.5V 0.8 V

Logic Input Current VON_ = 0V or VIN_ -1 +1 µA

FLT_ Output Low Voltage ISINK = 1mA 0.4 V

FLT_ Output High Leakage

Current VIN_ = V FLT_ = 5.5V 1 µA

Autorestart Current In latched-off state, VOUT_ = 0V 10 25 50 mA

Autorestart Threshold In latched-off state, rising 0.4 0.5 0.6 V

Autorestart Delay In latched-off state, VOUT_ > 1V 8 20 40 ms

ELECTRICAL CHARACTERISTICS

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩto GND, TA= -40°C to +85°C,

unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage Range 2.7 5.5 V

VIN_ = 5V, TA = +25°C75

Switch On-Resistance RON VIN_ = 4.4V, TA = 0°C to +85°C 105 mΩ

Standby Supply Current Both switches disabled 6 µA

Quiescent Supply Current Both switches enabled 75 µA

OUT_ Off-Leakage Current Switches disabled, VOUTA = VOUTB = 0V 10 µA

Undervoltage-Lockout Threshold VUVLO Rising edge, 3% hysteresis 2.3 2.7 V

Continuous Load Current RISET = 26kΩ1.2 A

RISET = 26kΩ1.20 1.60

RISET = 39kΩ0.80 1.05

Current-Limit Threshold VIN_ - VOUT_ = 0.5V

RISET = 60kΩ0.50 0.70

Peak Short-Circuit Current Limit ISHORT VOUT_ = 0V

(IOUT_ pulsing) RISET = 26kΩ1.45 2.60 A

(

PEAK

)

Fault-Blanking Timeout Period From ILIMIT condition to 50% of V FLT_ 840ms

Typical Operating Characteristics

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩto GND. Typical values are at TA=

+25°C, unless otherwise noted.)

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩto GND, TA= -40°C to +85°C,

unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Turn-On Delay tON

ROUT_ = 10Ω, COUT_ = 1µF, does not

include rise time (from ON asserted to

VOUT_ = 10% VIN_)

0.5 4.0 ms

Turn-Off Delay from ON tOFF

ROUT_ = 10Ω, COUT_ = 1µF, does not

include rise time (from ON deasserted to

VOUT_ = 90% VIN_)

1000 µs

VIN_ = 2.7V to 4.0V 1.6

ONA/ONB Logic Input High

Voltage VIH VIN_ = 4.0V to 5.5V 2.0 V

VIN_ = 2.7V to 4.0V 0.6

ONA/ONB Logic Input Low

Voltage VIL VIN_ = 4.0V to 5.5V 0.8 V

Logic Input Current VON_ = 0V or VIN_ -1 +1 µA

FLT_ Output Low Voltage ISINK = 1mA 0.4 V

FLT_ Output High Leakage

Current VIN_ = V FLT_ = 5.5V 1 µA

Autorestart Current In latched-off state, VOUT_ = 0V 10 50 mA

Autorestart Threshold In latched-off state, rising 0.4 0.6 V

Autorestart Delay In latched-off state, VOUT_ > 1V 8 40 ms

Note 3: Specifications from 0°C to -40°C are guaranteed by design but not 100% tested.

Note 4: The output voltage at which the device transitions from short-circuit current limit to continuous current limit. See the Output-

Current Fault Protection section.

CURRENT-LIMIT PROGRAM vs. RISET

MAX1558/58H toc01

RISET (kΩ)

CURRENT LIMIT (A)

40 48 52 564428 3632

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

1.6

0.5

24 60

QUIESCENT SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1558/58H toc02

SUPPLY VOLTAGE (V)

QUIESCENT CURRENT (µA)

54321

QUIESCENT CURRENT vs. TEMPERATURE

MAX1558/58H toc03

TEMPERATURE (°C)

QUIESCENT CURRENT (µA)

603510-15

-40 85

VIN_ = 5.5V

VIN_ = 4.5V

VIN_ = 5V

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 5

SHUTDOWN CURRENT vs. TEMPERATURE

MAX1558/58H toc04

TEMPERATURE (°C)

SHUTDOWN CURRENT (µA)

6035-15 10

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

-40 85

ON_ = VIN_ (MAX1558)

ON_ = GND (MAX1558H)

SWITCH OFF-LEAKAGE CURRENT

vs. TEMPERATURE

MAX1558

58H toc05

TEMPERATURE (°C)

SWITCH OFF-LEAKAGE CURRENT (nA)

6035-15 10

0.01

0.1

100

1000

-40 85

ON_ = IN_ (MAX1558)

ON_ = GND

(MAX1558H)

OFF REVERSE-BLOCKING LEAKAGE

CURRENT vs. OUTPUT VOLTAGE

MAX1558/58H toc06

OUTPUT VOLTAGE (V)

OFF REVERSE-BLOCKING LEAKAGE CURRRENT (nA)

54321

0.1

100

NORMALIZED ON-RESISTANCE

vs. TEMPERATURE

MAX1558/58H toc07

TEMPERATURE (°C)

NORMALIZED RON (Ω)

603510-15

0.75

1.00

1.25

1.50

0.50

-40 85

CONTINUOUS CURRENT-LIMIT THRESHOLD

vs. TEMPERATURE

MAX1558/58H toc08

TEMPERATURE (°C)

CONTINUOUS CURRENT-LIMIT THRESHOLD (A)

603510-15

1.40

1.42

1.41

1.39

1.38

1.37

1.36

1.44

1.43

1.45

1.35

-40 85

TURN-ON TIME

vs. TEMPERATURE (tON + tRISE)

MAX1558/58H toc09

TEMPERATURE (°C)

TURN-ON TIME (ms)

603510-15

-40 85

VIN_ = 4.5V

VIN_ = 5.5V

VIN_ = 5V

TURN-OFF TIME

vs. TEMPERATURE (tOFF + tFALL)

MAX1558/58H toc10

TEMPERATURE (°C)

TURN-OFF TIME (ms)

603510-15

2.75

3.00

3.25

3.50

3.75

4.00

2.00

2.25

2.50

-40 85

VIN_ = 4.5V

VIN_ = 5.5V

VIN_ = 5V

MAX1558/58H toc11

TEMPERATURE (°C)

655035205-10-25

-40 80

VIN_ = 4.5V

VIN_ = 5.5V

VIN_ = 5V

FAULT-BLANKING TIME (ms)

FAULT-BLANKING TIME

vs. TEMPERATURE

MAX1558/58H toc12

TEMPERATURE (°C)

603510-15

150

175

200

225

250

275

100

125

-40 85

VIN_ = 4.5V

VIN_ = 5.5V

VIN_ = 5V

FAULT OUTPUT LOW VOLTAGE (mV)

FAULT OUTPUT LOW VOLTAGE

vs. TEMPERATURE

Typical Operating Characteristics (continued)

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩto GND. Typical values are at TA=

+25°C, unless otherwise noted.)

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

6 _______________________________________________________________________________________

MAX1558/58H toc13

TEMPERATURE (°C)

603510-15

-40 85

VIN_ = 4.5V

VIN_ = 5.5V

VIN_ = 5V

AUTORESET CURRENT (mA)

AUTORESET CURRENT

vs. TEMPERATURE

AUTORESET CURRENT

vs. INPUT VOLTAGE

MAX1558/58H toc14

VIN (V)

AUTORESET CURRENT (mA)

5.55.04.54.03.5

3.0 6.0

TA = +85°C

TA = -40°C

TA = +25°C

OVERLOAD RESPONSE INTO 2.5Ω

MAX1558/58H toc15

20ms/div

IOUT_

OUT_

VIN

FLT_

5V/div

1A/div

SHORT-CIRCUIT RESPONSE INTO 0Ω

MAX1558/58H toc16

20ms/div

IOUT_

VIN

VOUT

FLTA_

5V/div

5A/div

SHORT

APPLIED

SHORT

REMOVED

SWITCH ON

AUTORESTART

Typical Operating Characteristics (continued)

(VINA = VINB = 5V, VONA = VONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩto GND. Typical values are at TA=

+25°C, unless otherwise noted.)

SWITCH TURN-ON TIME

MAX1558/58H toc17

2.0ms/div

ON_

OUT_

2V/div

SWITCH TURN-OFF TIME

MAX1558/58H toc18

1.0ms/div

ON_

OUT_

2V/div

Detailed Description

The MAX1558/MAX1558H are dual current-limited

switches designed for USB applications. They have two

independent switches, each with its own enable control

input and autoreset function. Each switch has an error-

flag output to notify the USB controller when current-

limit, short-circuit, undervoltage-lockout, or thermal-

shutdown conditions occur (Figure 2). The MAX1558/

MAX1558H operate from a 2.7V to 5.5V supply. Each

output can supply up to 1.2A. Current limit for both

channels is set with one external resistor.

The MAX1558/MAX1558H have independent thermal

shutdown for each switch in the event of a prolonged

overload. An autoreset function monitors the output and

automatically turns the switch on when the overload is

removed. Separate current limiting and thermal-shut-

down circuits permit each switch to operate indepen-

dently, improving system robustness.

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 7

PIN NAME FUNCTION

1 INA Power Input for OUTA. Connect INA and INB together and bypass with a 0.1µF capacitor to ground.

Load conditions may require additional bulk capacitance to prevent the input from being pulled down.

2ONA

*(ONA)

Control Input for Switch A. Can be driven higher than IN_ without damage. A logic low turns switch A on

for the MAX1558. A logic high turns switch A on for the MAX1558H.

3 ISET Current-Limit Adjust for Both Channels. Connect a resistor between 26kΩ to 60kΩ from ISET to ground to

program the current limit. See Setting the Current Limit in the Applications Information section.

4ONB

*(ONB)

Control Input for Switch B. Can be driven higher than IN_ without damage. A logic low turns switch B on

for the MAX1558. A logic high turns switch B on for the MAX1558H.

5 INB Power Input for OUTB. Connect INB and INA together and bypass with a 0.1µF capacitor to ground.

Load conditions may require additional bulk capacitance to prevent the input from being pulled down.

6 OUTB Power Output for Switch B. Connect a 1µF capacitor from OUTB to ground. The load condition may

require additional bulk capacitance.

7FLTB Fault Indicator Output for Switch B. This open-drain output goes low when switch B is in thermal

shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition.

8 GND Ground

9FLTA Fault Indicator Output for Switch A. This open-drain output goes low when switch A is in thermal

shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition.

10 OUTA Power Output for Switch A. Connect a 1µF capacitor from OUTA to ground. The load condition may

require additional bulk capacitance.

— PAD Exposed Pad, Internally Connected to GND. Connect exposed pad to a large copper trace for maximum

power dissipation.

Pin Description

*( ) are for the MAX1558H only.

MAX1558

INPUT

2.7V TO 5.5V

INA

INB

ISET

FLTA

FLTB

ONA

ONB

ONA

ONB

OUTA

OUTB

GND

USB

PORT A

USB

PORT B

0.1µF

100kΩ

1µF*

*USB APPLICATIONS MAY REQUIRE ADDITIONAL

BULK CAPACITANCE

Figure 1. Typical Application Circuit

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

8 _______________________________________________________________________________________

MAX1558

CHARGE

PUMP

BIAS

UVLO

REF

OSC

25kHz

TIMER

20ms

THERMAL

SHUTDOWN

CHARGE

PUMP

ILIMB

ILIMA

30mA

INA

ONA

ONB

INB

ISET

ONA

ONB

FAULT

LOGIC

30mA

FLTB

INB

OUTB

GND

OUTA

FLTA

INA

0.6V

PROGRAM ILIMA

PROGRAM ILIMB

Figure 2. Functional Diagram

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 9

Undervoltage Lockout and

Input Voltage Requirements

The MAX1558/MAX1558H include a UVLO circuit to

prevent erroneous switch operation when the input volt-

age is low during startup and brownout conditions.

Operation is inhibited when VIN_ is less than 2.5V.

Output-Current Fault Protection

The current limit for both switch outputs is programmed

by a resistor between 26kΩand 60kΩconnected from

ISET to ground. See the Current-Limit Program Level vs.

RISET curve in the Typical Operating Characteristics and

Setting the Current Limit in the Applications Information

section. The MAX1558 reduces the gate drive to the

MOSFET switch when the programmed current-limit value

is reached. If the current-limit program value is reached,

the part reduces gate drive to regulate at the current limit.

If the current limit persists for 20ms (typ), the output turns

off and the fault flag is set until the fault is removed, as

detected by the autoreset circuit.

When the the output drops below 1V (typ), the current

limit is set 30% above the programmed level and

pulsed. This lowers the RMS current for a short-circuit

condition, which reduces system load current and

power dissipation. If a short circuit persists for 20ms,

the output turns off and the fault flag is set. The autore-

set circuit automatically restarts the part if the fault is

removed.

Fault Blanking

The MAX1558/MAX1558H switches can reach current

limit in normal operation when powering up or driving

heavy capacitive loads. To differentiate these conditions

from short circuits or sustained overloads, the

MAX1558/MAX1558H have independent fault-blanking

circuits in each switch. When a load transient causes

the device to enter the current limit, an internal counter

monitors the duration of the fault. For load faults exceed-

ing the 20ms fault-blanking time, the offending switch

turns off, the corresponding FLT_ signal asserts low,

and that channel enters autoreset mode (see the

Autoreset Mode section). Only current-limit and short-

circuit faults are blanked. Thermal-overload faults and

input-voltage drops below the UVLO threshold immedi-

ately cause the switch to turn off and FLT_ to assert low.

Fault blanking allows the MAX1558 to handle USB

loads that may not be fully compliant with USB specifi-

cations. USB loads with additional bypass capacitance

and/or large startup currents can be successfully pow-

ered even while protecting the upstream power source.

No fault is indicated if the switch is able to bring up the

load within the 20ms blanking period.

Autoreset Mode

If an output fault is detected for more than the 20ms

blanking time, the output latches off and the FLT_ out-

put goes low. The MAX1558/MAX1558H then source

30mA to the faulted output and monitor the output volt-

age to determine when the overload is removed. If the

voltage on the output rises above 0.5V for more than

20ms, the fault resets and the output turns on. The

MAX1558 can also be reset from fault manually by tog-

gling ON_ (ON_ for the MAX1558H) for that channel.

Reverse Current Blocking

The USB specification does not allow an output device

to source current back into the USB port. However, the

MAX1558/MAX1558H are designed to safely power

noncompliant devices. When disabled, each output is

switched to a high-impedance state, blocking reverse-

current flow from the output back to the input. However,

during normal operation with the device enabled, the

MAX1558/MAX1558H are bidirectional switches.

Thermal Shutdown

The MAX1558/MAX1558H feature independent thermal

shutdown for each switch channel, allowing one switch

to deliver power even if the other switch has a fault con-

dition. When the junction temperature exceeds +160°C,

the switch turns off and the FLT_ output goes low imme-

diately; fault blanking does not occur during thermal

limit. When the junction cools by 10°C, the switch turns

on again. If the fault-overload condition continues, the

switch cycles on and off, resulting in a pulsed output,

saving battery power.

Fault Indicators

The MAX1558/MAX1558H provide an open-drain fault

output (FLT_) for each switch. For most applications, con-

nect FLT_ to IN_ through a 100kΩpullup resistor. FLT_

goes low when any of the following conditions occur:

• The input voltage is below the UVLO threshold.

• The switch junction temperature exceeds the +160°C

thermal-shutdown temperature limit.

• The switch is in current-limit or short-circuit limit mode

after the 20ms fault-blanking period is exceeded.

• The switch is in autoreset mode.

After the fault condition is removed, the FLT_ output

deasserts after a 20ms delay. Ensure that the

MAX1558/MAX1558H have adequate input bypass

capacitance to prevent glitches from triggering FLT_ out-

puts. Glitches that cause the input supply to drop below

2.5V may cause the undervoltage lockout to trigger, turn-

ing the outputs off and asserting the FLT signals.

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

10 ______________________________________________________________________________________

Applications Information

Setting the Current Limit

A resistor from ISET to ground programs the current-

limit value for both outputs. Use a resistor between

26kΩand 86kΩto set the current limit according to

the formula:

ILIM(TYPICAL) = 36400 / RISET (Amps)

Do not use RISET values below 26kΩbecause the maxi-

mum current rating of the device may be exceeded.

RISET values larger than 60kΩare not recommended

and do not provide a lower limit current than 500mA.

If the output drops below 1V (typ), the MAX1558 shifts

to a short-circuit current-limit threshold that is 30%

above the programmed level given by the ILIM(TYPICAL)

formula. If the short-circuit threshold is exceeded, the

switch shuts off immediately (no 20ms delay) and

ramps the current back up in approximately 3ms. If the

short persists and the current ramps all the way up to

the short-circuit limit again, the switch again turns off. If

the short still persists, the output pulses this way for

20ms, at which time the switch turns off and autoreset

mode begins.

Input Capacitor

INA and INB provide the power for all control and

charge-pump circuitry and must be connected together

externally. Connect a capacitor from IN_ to ground to

limit the input-voltage drop during momentary output

short-circuit conditions. A 0.1µF ceramic capacitor is

required for local decoupling; higher capacitor values

further reduce the voltage drop at the input. When dri-

ving inductive loads, a larger capacitance prevents

voltage spikes from exceeding the MAX1558/

MAX1558Hs’ absolute maximum ratings.

Output Capacitor

Place a 1µF or greater capacitor at each output for

noise immunity. When starting up into very large capac-

itive loads, the switch may pulse the output current at

the short-circuit current-limit program level until the out-

put voltage rises above 1V. Then, the capacitor contin-

ues to charge at the full, continuous current-limit

program level. There is no limit to the output capacitor

size, but to prevent a startup fault assertion, the capaci-

tor must charge up within the fault-blanking delay peri-

od. Typically, starting up into a 500µF or smaller

capacitor does not trigger a fault output. In addition to

bulk capacitance, small-value (0.1µF or greater) ceram-

ic capacitors improve the output’s resilience to electro-

static discharge (ESD).

Driving Inductive Loads

A wide variety of devices (mice, keyboards, cameras,

and printers) can load the USB port. These devices com-

monly connect to the port with cables, which can add an

inductive component to the load. This inductance caus-

es the output voltage at the USB port to ring during a

load step. The MAX1558/MAX1558H are capable of dri-

ving inductive loads, but avoid exceeding the devices’

absolute maximum ratings. Usually the load inductance

is relatively small, and the MAX1558/MAX1558Hs’

input includes a substantial bulk capacitance from an

upstream regulator as well as local bypass capacitors,

limiting overshoot. If severe ringing occurs due to large

load inductance, clamp the MAX1558/MAX1558Hs’ out-

put below +6V and above -0.3V.

Turn-On and Turn-Off Behavior

In the absence of faults, the MAX1558/MAX1558Hs’

internal switches turn on and off slowly under the control

of the ON_ inputs. Transition times for both edges are

approximately 4ms. The slow charge-pump switch drive

minimizes load transients on the upstream power source.

Under thermal fault and UVLO, the power device turns

off rapidly (100ns) to protect the power device.

Layout and Thermal Dissipation

To optimize the switch response time to output short-

circuit conditions, keep all traces as short as possible

to reduce the effect of undesirable parasitic induc-

tance. Place input and output capacitors no more than

5mm from device leads. All IN_ and OUT_ pins must be

connected with short traces to the power bus. Wide

power-bus planes provide superior heat dissipation

through the switch IN_ and OUT_ pins. While the

switches are on, power dissipation is small and the

package temperature change is minimal. Calculate the

power dissipation for this condition as follows:

P = (IOUT_)2RON

For the maximum operating current (IOUT_ = 1.2A) and

the maximum on-resistance of the switch (125mΩ), the

power dissipation is:

P = (1.2A)2x 0.125Ω= 180mW per switch

The worst-case power dissipation occurs when the

switch is in current limit and the output is greater than

1V. The instantaneous power dissipated in each switch

is the voltage drop across the switch multiplied by the

current limit. The fault-blanking circuit turns the output

off if the fault persists for 20ms, while the autoreset cir-

cuit can turn it back on after 20ms in the off state. Thus,

the average worst-case power is approximately 50% of

the instantaneous value.

P = 0.5 x (ILIM) x (VIN_ - VOUT_)

For a 5V input and 1V output, the maximum possible

power dissipation per switch is:

P = 0.5 x (1.5A) x (5V - 1V) = 3W

Since the package power dissipation is limited to

1952mW, the MAX1558/MAX1558H die temperature

exceeds the thermal-shutdown threshold and the

switch turns off. After the die temperature cools by

10°C, the switch turns on again. If the fault-overload

condition continues, the switch cycles on and off with a

duty cycle and period that is a function of the ambient

temperature and PC board layout.

A short across the output for more than 20ms places

the part in autoreset mode. With VIN_ = 5V and an

autoreset test current of 30mA, the power dissipation

for a short-circuited output is given by:

P = (30mA) x 5V = 0.15W

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

______________________________________________________________________________________ 11

Chip Information

TRANSISTOR COUNT: 2932

PROCESS: BiCMOS

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

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.

12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to www.maxim-ic.com/packages.)

6, 8, &10L, DFN THIN.EPS

PIN 1

INDEX

AREA

DETAIL A

21-0137

PACKAGE OUTLINE, 6,8,10 & 14L,

TDFN, EXPOSED PAD, 3x3x0.80 mm

-DRAWING NOT TO SCALE-

COMMON DIMENSIONS

SYMBOL MIN. MAX.

A0.70 0.80

D2.90 3.10

E2.90 3.10

A1 0.00 0.05

L0.20 0.40

PKG. CODE ND2 E2 eJEDEC SPEC b[(N/2)-1] x e

PACKAGE VARIATIONS

0.25 MIN.k

A2 0.20 REF.

2.30±0.101.50±0.106T633-1 0.95 BSC MO229 / WEEA 1.90 REF0.40±0.05

1.95 REF0.30±0.05

0.65 BSC

2.30±0.108T833-1

2.00 REF0.25±0.050.50 BSC2.30±0.1010T1033-1

2.40 REF0.20±0.05- - - - 0.40 BSC1.70±0.10 2.30±0.1014T1433-1

1.50±0.10

MO229 / WEEC

MO229 / WEED-3

0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-2 14 2.30±0.101.70±0.10

T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF

T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

-DRAWING NOT TO SCALE-

21-0137

PACKAGE OUTLINE, 6,8,10 & 14L,

TDFN, EXPOSED PAD, 3x3x0.80 mm

DOWNBONDS

ALLOWED

YES