DS1780E/T&R - Maxim Integrated

1 of 28 032305

FEATURES

§ Direct-to-digital temperature sensor requires

no external components or user calibration

§ Two fan speed sensors

§ Monitors 6 power supply voltages

§ 8-bit DAC for fan speed control

§ Intrusion detect for security (detects when

chassis lid has been removed, even if power is

off)

§ Remote system reset

§ System interrupt availability on all monitored

functions (temperature, voltages, fan speed,

chassis intrusion)

§ 2-wire interface with 2-bit addressability

§ Integrated NAND TREE for board level

testability

§ Wide power supply range (2.8V £ VDD £

5.75V)

§ High integration in a small 24-pin 173-mil

TSSOP

§ Applications include monitoring of personal

computers or any microprocessor-based

system

PIN ASSIGNMENT

PIN DESCRIPTION

A0/NTOUT - Address Input / NAND

TREE Output

A1 - Address Input

SDA - 2-Wire Serial Data

Input/Output

SCL - 2-Wire Serial Clock

FANx - Tachometer Inputs

CHS - Chassis Intrusion Detector

Input

GNDD - Digital Ground

VDD - Power Supply Voltage (2.8V

to 5.75V)

INT - Hardware Interrupt output

VOUT/NTIN - DAC output / NAND TREE

Input

RST - Remote System Reset

GNDA - Analog Ground

+xxVIN - Positive Voltage Inputs

+2.5VS/+VCCP2 - Positive/negative Voltage

Input

VIDx - Processor Voltage Supply

Readout Inputs

See Table 11 on page 27 for Ordering Information

DS1780

CPU Peripheral Monito

www.dalsemi.com

DS1780E+

24-Pin TSSOP

(

173-mil

)

VID0

VID

VID2

VID3

VID4

+VCCP1

+2.5 VIN

+3.3 VIN

+5 VIN

+12 VIN

+2.5 VS/+VCCP2

GNDA

FAN1

CHS

GNDD

VDD

INT

VOUT

NTIN

RST

SCL

FAN2

A0/NTOUT

DS1780

2 of 28

DESCRIPTION

The DS1780 is a highly integrated system instrumentation monitor ideal for use in personal computers, or

any microprocessor-based system. It monitors ambient temperature, six power supply voltages, and the

speed of two fans. Fan speed can also be controlled with the use of an internal 8-bit DAC. All

measurements are internally converted to a digital format for easy processing by the CPU.

The DS1780 can be reset to its default power-up state via a remote reset function with internal debounce

and delay. It features an interrupt that can be programmed to become active should any of the functions

the DS1780 is monitoring fall out of spec.

For board-level testability, an internal NAND TREE function simplifies the system design. A chassis

intrusion input is featured to enhance system security.

Programming and data readout are accessed via a simple 2-wire interface with 2-bit addressability. The

DS1780 power supply range of 2.8V to 5.75V allows for monitoring of parameters for 3V or 5V systems.

The DS1780 is assembled in a compact 173-mil TSSOP package.

Detailed Pin Description Table 1

PIN SIGNAL DIRECTION DESCRIPTION

1 A0/NTOUT Digital I/O

The lowest order programmable bit of the 2-wire bus address. This pin

functions as an output when doing a NAND TREE test.

2 A1 Digital Input The highest order programmable bit of the 2-wire bus address.

3 SDA Digital I/O 2-wire bus bi-directional data. Open-drain output.

4 SCL Digital Input 2-wire bus synchronous clock.

5 FAN1 Digital Input 0 to VDD amplitude fan tachometer input.

6 FAN2 Digital Input 0 to VDD amplitude fan tachometer input.

7 CHS Digital I/O

An active high input from an external circuit, which latches a Chassis

Intrusion event. This line can go high without any clamping action regardless

of the powered state of the DS1780. The DS1780 provides an internal open

drain on this line, controlled by Bit 6 of Configuration Register, to provide a

minimum 20 ms reset of this signal.

8 GNDD GROUND Internally connected to all digital circuitry.

9 VDD POWER

+3.3V or +5V VDD power. Bypass with the parallel combination of 10 µF

(Electrolytic or Tantalum) and 0.1 µF (ceramic) bypass capacitors.

10 INT Digital Output Active-low Programmable interrupt output. The output is enabled when Bit 1

of the Configuration Register is set to 1. The default state is disabled.

11 VOUT/NTIN Digital Input/

Analog Output

An active-high input that enables NAND Tree board-level connectivity

testing. Refer to “NAND Tree Testing” Section. Used as DAC output when

NAND Tree is not selected.

12 RST Digital I/O

Master Reset, 5 mA open drain driver, active low output with at least a 20 ms

minimum pulse width. Available when enabled via Bit 4 in Configuration

13 GNDA GROUND

Internally connected to all analog circuitry. The ground reference for all

analog inputs.

14 +2.5VS/+VCCP2 Analog Input

Analog input for monitoring -12V or +VCCP2. DS1780 will measure voltages

on this pin from 0V to 3.6V. An external resistor ladder is required for

monitoring a -12V supply (see Figure 1).

15-19 +xxVIN Analog Inputs A/D inputs for 5 positive voltages.

20-24 VIDx Digital Inputs

Voltage supply readouts from the processor. These values are read in the VID

and VID4 Status Registers.

DS1780

3 of 28

OVERVIEW

A block diagram of the DS1780 is shown in Figure 1.

The DS1780 provides six analog inputs, an analog output, five digital inputs, two fan speed inputs, a

temperature sensor, and interrupt registers on a single chip, which communicates on a 2-wire serial bus.

The DS1780 performs power supply, temperature, and fan monitoring for personal computers.

The analog voltages are divided internally by the DS1780. The inputs are then converted to 8-bit digital

words. The analog inputs are intended to be connected to the several power supplies present in a typical

computer. Temperature can be converted to a 9-bit two’s-complement digital word with a 0.5°C LSb.

The analog output is approximately a 0-1.25V output from an 8-bit D/A converter, which is used to

control fan speeds.

Fan inputs measure the period of tachometer pulses from the fans, providing a higher count for lower fan

speeds. The fan inputs are digital inputs with an acceptable range of 0 to VDD volts and a transition level

of approximately 1.4 volts. Full-scale fan counts are 255 (8-bit counter) and this represents a stopped or

very slow fan. Nominal speeds, based on a count of 153, are programmable from 1100 to 8800 RPM on

FAN1 and FAN2. Signal conditioning circuitry is included to accommodate slow rise and fall times.

The DS1780 provides a number of internal registers, as detailed in Table 1. These include:

Configuration Register: Provides control and configuration, as well as initialization.

Interrupt ( INT ) Status Registers: Two registers to provide status of each interrupt limit or interrupt

event.

Interrupt ( INT ) Mask Registers: Allows masking of individual Interrupt sources, as well as separate

masking for the hardware interrupt output.

Temperature Configuration Register: The lower 2 bits of this register configure the type of

temperature interrupt mode to be used. Bit 7 reflects the lowest bit of the temperature reading.

VID Register, VID4 Register: Bits 0-3 of the VID register reflect the status of the VID0-VID3 pins, bit

0 of the VID4 register reflect the status of VID4 pin. These are simply input pins - not processed in any

way. In a multiprocessor system, these signals will be multiplexed externally from the various processor

sources, with the source being controlled by software.

Value RAM: The monitoring results and limits for temperature, voltages, and fan counts are all

contained in the Value RAM.

When the DS1780 is started, it cycles through each measurement in sequence, and it continuously loops

through the sequence approximately once every second. Each measured value is compared to values

stored in limit registers. When the measured value violates the programmed limit the DS1780 will set a

corresponding System Management Interrupt (SMI) in the Interrupt Status Registers. One hardware

interrupt line, INT , is available to generate an SMI. INT is fully programmable with masking of each

Interrupt source, and masking of the output. In addition, the configuration register has control bits to

enable or disable the hardware Interrupts.

DS1780

4 of 28

A CHS (Chassis Intrusion) digital input is provided. The Chassis Intrusion input is designed to accept an

active high signal from an external circuit that latches when the case is removed from the computer; this

pin is a dual purpose pin which will be driven low by the DS1780 to reset the external circuit.

DS1780 FUNCTIONAL BLOCK DIAGRAM Figure 1

Note: R1 and R2 on the -12V resistance ladder should be ratioed such that approximately +2.5V appears

at the input pin (i.e., R1=4kΩ, R2=23.2 kΩ). If a second processor voltage needs to be monitored (VCCP2),

leave R2 empty, and make R1 500Ω, with VCCP2 appearing here.

2-WIRE SERIAL DATA BUS

When using the 2-wire bus, a write will always consist of the DS1780 2-wire slave address, followed by

the Internal Address Register byte, then the data byte. The Internal Address Register addresses are listed

below in Table 2. There are two cases for a read:

1. If the Internal Address Register is known to be at the desired Address, simply read the DS1780 with

the 2-wire slave address, followed by the data byte read from the DS1780.

2. If the Internal Address Register value is unknown, write to the DS1780 with the 2-wire slave address,

followed by the Internal Address Register byte. Then restart the Serial Communication with a Read

consisting of the 2-wire slave address, followed by the data byte read from the DS1780.

The default power-on 2-wire slave address for the DS1780 is 01011(A1)(A0) binary, where A0-A1

reflects the state of the pins defined by the same names. The address can be changed by writing any

desired value to the 2-wire Serial Address Register (excluding the 2 LSBs). This communication protocol

is depicted in the 2-wire timing diagrams of Figures 2 and 8.

DS1780

5 of 28

INTERNAL ADDRESS REGISTER MAP Table 2

HEX ADDRESS POWER ON VALUE NOTES

Configuration Register 40h 0000 1000

Interrupt (INT) Status

Interrupt (INT) Mask

Chassis Intrusion Clear

Bit 7 of this register

clears Chassis Intrusion.

The other bits are

reserved.

VID Register 47h 0101 XXXX

The lower 4 bits reflect

the state of

VID0-VID3 pins.

Serial Address Register 48h 0010 11XY X Reflects state of A1

and Y Reflects A0 state

VID4 Register 49h 1000 000X Bit 0 = VID 4. The rest

are reserved.

Temperature

Configuration

4Bh 0000 0001

Test Register 15h 0000 0000 Do not alter the

contents of the register.

Analog output 19h 1111 1111 Full on

Value RAM 20h-3Dh

Company ID 3Eh 1101 1010 Read only

Stepping 3Fh 0000 0001 Read only

DS1780

6 of 28

2-WIRE SERIAL COMMUNICATION WITH THE DS1780 Figure 2

OPERATION - Power-on

Applying power to the DS1780 causes a reset of several of the registers. Power-on conditions of the

registers are shown in Table 2 above. Some registers have indeterminate power-on values, such as the

Limit and RAM registers of the Value RAM page, and these are not shown in the table. Upon power-up

the ADC is inactive. Writing Limits into the Value RAM should usually be the first action performed

after power up. The RST pin is bi-directional. It forces RESET at power-on, but can also be pulled low to

force RESET internally.

OPERATION - Resets

The DS1780 features four distinct resetting functions. Each one has a different effect on register contents

and the state of the RST output following the event. Each one is explained below:

Power-on Reset - On POR, all internal logic is reset, and registers are cleared to their default state (see

tables 10.x). Because Value RAM is typically the first area programmed upon power-up, it does not have

a defined state upon POR. Also, on POR, the RST output will be pulled to an active low state for 20 ms

(minimum).

A POR occurs every time VDD crosses the voltage level approximately equivalent to the sum of one n-

channel threshold (VTN) and one p-channel threshold (VTP), on a power-up or power-down condition.

DS1780 SRAM contents get “scrambled” when VDD falls below the greater of one n-channel VT or one p-

channel VT. Therefore, SRAM contents will always be in a defined state as supply voltage reaches the

minimum spec level of 2.8V, even in a power supply brownout condition.

DS1780

7 of 28

Software Reset - This condition is generated by writing a 1 to bit 4 of the configuration register. It has no

effect on DS1780 register contents. It will however pull the RST output to the active low state for a

duration of 20 ms (minimum). When the RST output goes active, this bit in the configuration register will

clear itself. A Software Reset is only possible if Bit 7 of the INT Mask Register 2 (0x44h) is set to “1”.

Device Initialization - This condition is generated by writing a 1 to bit 7 of the configuration register. It

will clear all registers in DS1780 memory to their default state except the Value RAM (0x20h - 0x3Dh)

and analog output (0x19h). These locations will remain unchanged from their state before the

initialization. This condition has no effect on the RST output. This bit is self-clearing.

Hardware Reset - This condition is generated by some external source pulling the RST pin below

VIN(0) (see DC Electrical Characteristics). The DS1780 will then force the RST signal to remain in the

active low state for >20 ms. It will clear all registers in DS1780 memory to their default state except the

Value RAM (0x20h - 0x3Dh) and analog output (0x19h). These locations will remain unchanged from

their state before the Hardware Reset.

OPERATION - Configuration Register

Control of the DS1780 is provided through the configuration register. The Configuration Register is used

to start and stop the DS1780, enable or disable interrupt output and modes, and provide the initialization

function described above.

Bit 0 of the Configuration Register controls the monitoring loop of the DS1780. Setting Bit 0 low stops

the monitoring loop and puts the DS1780 into a standby mode. 2-Wire Bus communication is still

possible with any register in the DS1780 during the standby mode, however. Additionally, the DS1780

will continue to monitor the RST and CHS inputs while in a standby mode. Setting Bit 0 high starts the

monitoring loop.

Bit 1 of the Configuration Register enables or disables the INT Interrupt output. Setting Bit 1 high

enables the INT output, setting bit 1 low disables the output.

Bit 3 of the Configuration Register is used to clear the INT interrupt output when set high. The DS1780

monitoring function will stop until bit 3 is set low. Interrupt Status register contents will not be affected.

Bit 4 of the Configuration Register is used to initiate a minimum 20 ms RESET signal on the RST output

if the pin is configured for the RESET mode (via bit 7 of the INT Mask Register 2 - 0x44h).

Bit 6 of the Configuration Register is used to reset the Chassis Intrusion (CHS) output pin when set high.

Bit 7 of the Configuration Register is used to start a Configuration Register Initialization when taken

high, as described in the “OPERATION - Resets” section.

OPERATION - Monitoring Loop

The DS1780 monitoring function is started by doing a write to the Configuration Register and setting the

INT_Clear (Bit 3) low, and Start (Bit 0) high. At this point the INT_Enable (Bit 1) should be set high to

enable interrupts (INT). The DS1780 then performs a “round robin” sampling of the inputs, sampling

each approximately once a second, in the order (corresponding to locations in the Value RAM) shown

below in Table 3. The results of the sampling and conversions can be found in the Value RAM (Table

10.13) and are available at any time.

DS1780

8 of 28

DS1780 MONITORING ORDER Table 3

TEMPERATURE READING

ANALOG +2.5 VS/VCCP2

ANALOG +12V

ANALOG +5V

ANALOG +3.3V

ANALOG +2.5V

ANALOG +VCCP1

FAN1

FAN2

If conversions are terminated by either of the methods described in the “OPERATION - Configuration

Monitoring will then terminate. When the monitoring again commences, monitoring always starts with

the temperature reading.

OPERATION - Temperature Data Format

The DS1780 internally converts measured temperature data to a two’s complement data format (in °C).

The host can read the last completed temperature conversion at any time by setting the Internal Address

below in Table 4. The MSb of the register represents the sign bit of the temperature reading. For

Fahrenheit usage, a lookup table or conversion routine must be used.

TEMPERATURE/DATA RELATIONSHIPS Table 4

S 26 2

5 2

4 2

3 2

2 2

1 2

MSb (unit = °C) LSb

TEMPERATURE DIGITAL OUTPUT

(BINARY) DIGITAL OUTPUT (HEX)

+125°C 0111 1101 7Dh

+25°C 0001 1001 19h

+1°C 0000 0001 01h

0°C 0000 0000 00h

-1°C 1111 1111 FFh

-25°C 1110 0111 E7h

-40°C 1101 1000 D8h

OPERATION - Voltage Data Format

The DS1780 contains inputs for directly monitoring the power supplies typically found in a PC (+12V, -

12V, +5V, +3.3V, +2.5V, +VCCP). These inputs are scaled internally to a reference source, and converted

via an 8-bit Delta-Sigma ADC (Analog-to-Digital Converter), thus allowing for a more accurate means of

measurement since the voltages are referenced to a known value.

Since these inputs can be greater than VDD, they are not diode protected to the power rails. In addition,

small external series resistors such as 510Ω should be put into the lines driving the DS1780 to prevent

damaging the traces or power supplies should an accidental short connect two power supplies together.

DS1780

9 of 28

The worse such accident would be connecting -12V to +12V; a total of 24V difference, with the series

resistors this would draw a maximum of approximately 24 ma.

The internal scaling factor depends upon the particular input. The +12VIN, +5VIN, +3.3VIN, and +2.5VIN

inputs are internally scaled such that the nominal value of the respective supply corresponds to 3/4 of full

range, or a decimal count of 192. The approximate resolution is thus equal to:

LSb (VNOM) @ 256

V 4/3 NOM

This is depicted below in Table 5.

VOLTAGE/DATA RELATIONSHIPS FOR POSITIVE ONLY VOLTAGE INPUTS

(+12VIN, +5VIN, +3.3VIN, and +2.5VIN) Table 5

INPUT PIN +12VIN +5VIN +3.3VIN +2.5VIN

LSb WEIGHTING

(mV)

62.5 26.0 17.2 13.0

ADC RESULT (BASE

10)

PIN VOLTAGE (V) PIN VOLTAGE (V) PIN VOLTAGE (V) PIN VOLTAGE (V)

0 0 0 0 0

1 0.063 0.026 0.017 0.013

2 0.125 0.052 0.034 0.026

3 0.188 0.078 0.052 0.039

4 0.25 0.104 0.069 0.052

•

190 11.875 4.948 3.266 2.474

191 11.938 4.974 3.283 2.487

192 12.0 5.0 3.3 2.5

193 12.063 5.026 3.317 2.513

•

252 15.75 6.563 4.331 3.281

253 15.813 6.589 4.348 3.294

254 15.875 6.615 4.366 3.307

255 15.938 6.641 4.383 3.32

The other two voltage inputs use a slightly different scaling technique, due to the nature of the PC voltage

they are monitoring. Because processor voltage (VCCP) can vary to 3.6V, the +VCCP1 and +2.5VS/+VCCP1

inputs are internally scaled such that the ADC result is 0h for a 0V input and the maximum value of FFh

is returned for a voltage of 3.60V. This corresponds to an LSb weighting of 14.1 mV.

The inputs can also be used to monitor a negative supply, such as -12V. However, a resistor ladder and

positive reference voltage (VREF) must be used (see Figure 1) such that input voltage to the DS1780

swings between OV and +3.6V. Assuming the DS1780 +VCCP1 and +2.5VS/+VCCP2 pins have infinite

input impedance and the VREF is a perfect supply, then the resolution and range of -12V input are:

LSb (R1, R2) @ 255

3.6 ú

é+

DS1780

10 of 28

VMIN (VREF, R1, R2) @ -

R VREF

VMAX (VREF, R1, R2) @ VREF-(VREF-3.6) ú

é+

If the +2.5VS/+VCCP2 is to be used to monitor a secondary processor core voltage (VCCP2), R2 should be

removed and R1=500Ω. Table 6 below shows the voltage/data relationship for these inputs in the ideal

case. In this example, VREF=+5.0V, R1=4.0 kΩ, and R2=23.2 kΩ.

Analog inputs will provide best accuracy when referred to the GNDA pin. A separate, low-impedance

ground plane for analog ground, which provides a ground point for the voltage dividers and analog

components will provide best performance but is not mandatory. Analog components such as voltage

dividers should be located physically as close as possible to the DS1780.

The power supply bypass, the parallel combination of 10 µF (electrolytic or tantalum) and 0.1 µF

(ceramic) bypass capacitors connected between pin 9 and ground, should also be located as close as

possible to the DS1780.

VOLTAGE/DATA RELATIONSHIPS FOR VCCP VOLTAGE INPUTS

(+VCCP1, +2.5VS/ +VCCP2) Table 6

INPUT PIN +VCCP1 +2.5VS/+VCCP2

LSb WEIGHTING (mV) 14.1 96.0

(Used to monitor VCCP) (Used to monitor -12V)

ADC RESULT (BASE 10) PIN VOLTAGE (V) SUPPLY VOLTAGE (V)

0 0 -29.0

1 0.014 -28.90

2 0.028 -28.81

3 0.042 -28.71

4 0.056 -28.62

•

136 1.920 -15.94

137 1.934 -15.85

138 1.948 -15.75

139 1.962 -15.66

•

252 3.558 -4.808

253 3.572 -4.712

254 3.586 -4.616

255 3.60 -4.52

OPERATION - FAN Speed Data Format

Inputs are provided for signals from fans equipped with tachometer outputs. These are logic-level inputs

with an approximate threshold of 1.4V. Signal conditioning in the DS1780 accommodates the slow rise

and fall times typical of fan tachometer outputs. The maximum input signal range is 0 to VDD. In the

event these inputs are supplied from fan outputs which exceed 0 to VDD, either resistive division or diode

clamping must be included to keep inputs within an acceptable range, as shown in Figure 3. R2 is

selected so that it does not develop excessive voltage due to input leakage. R1 is selected based on R2 to

provide a minimum input of 2V and a maximum of VDD. R1 should be as low as possible to provide the

DS1780

11 of 28

maximum possible input up to VDD for best noise immunity. Alternatively, use a shunt reference or Zener

diode to clamp the input level.

Tables 7 and 8 describe the format of the data stored in the FAN reading registers (Internal Address

Registers 28h and 29h).

FAN TACHOMETER INPUT OPTIONS Figure 3

VOLTAGE/DATA RELATIONSHIPS FOR FAN INPUTS (FAN1, FAN2) UNDER

DEFAULT (÷2) MODE Table 7

RPM Timer Per Revolution Counts for “Divide by 2” (default mode) in decimal Comments

4400 13.64 ms 153 Typical RPM

3080 19.48 ms 219 70% RPM

2640 22.73 ms 255 (maximum) 60% RPM

VOLTAGE/DATA RELATIONSHIPS FOR FAN INPUTS (FAN1, FAN 2) Table 8

MODE

SELECT

NOMINAL

RPM

TIME PER

REVOLUTION

COUNTS FOR THE

NOMINAL

SPEED IN DECIMAL

70% RPM

TIME PER

REVOLUTION FOR

70% RPM

Divide by 1 8800 6.82 ms 153 6160 9.74 ms

Divide by 2 4400 13.64 ms 153 3080 19.48 ms

Divide by 4 2200 27.27 ms 153 1540 38.96 ms

Divide by 8 1100 54.54 ms 153 770 77.92 ms

In general, the value stored in the FAN registers (in decimal) follows the equation:

Count (RPM, Divisor) @ Divisor RPM

10 x 1.35 6

If fans can be powered while the power to the DS1780 is off, the DS1780 inputs will provide diode

clamping. Limit input current to the Input Current at Any Pin specification shown in the ABSOLUTE

MAXIMUM RATINGS section. In most cases, open collector outputs with pullup resistors inherently

limit this current. If this maximum current could be exceeded, either a larger pullup resistor should be

used or resistors connected in series with the fan inputs.

The Fan Inputs gate an internal 22.5 kHz oscillator for one period of the Fan signal into an 8-bit counter

(maximum count = 255). The default divisor, located in the Fan Divisor/RST_Register, is set to 2

(choices are 1, 2, 4, and 8) providing a nominal count of 153 for a 4400 rpm fan with two pulses per

revolution. Typical practice is to consider 70% of normal RPM a fan failure, at which point the count will

be 219.

DS1780

12 of 28

OPERATION - Interrupts

An external interrupt can come from the following sources. While the label suggests a specific type or

source of interrupt, this label is not a restriction on the usage; it could come from any desired source.

1. Analog Voltage: An interrupt will be generated if a analog voltage high or low limit has been

exceeded; this is generally when a power supply is out of its normal operating range.

2. Temperature: An interrupt will be generated if a high or a low hot temperature limit has been

exceeded.

3. Fan speed: An interrupt will be generated if a fan count limit has been exceeded.

4. Chassis Intrusion: This is an active high interrupt from any type of device that detects and captures

chassis intrusion violations. This could be accomplished mechanically, optically, or electrically, and

circuitry external to the DS1780 is expected to latch the event.

All System Management Interrupts (SMIs) are indicated in the two Interrupt Status Registers. The INT

output has individual mask registers and individual masks for each Interrupt. As described in the

“OPERATION - Configuration Register” Section, this hardware Interrupt line can also be

enabled/disabled in the Configuration Register.

Reading an Interrupt Status Register will output the contents of the Register, and reset the Register. A

subsequent read done before the analog ‘round-robin’ monitoring loop is complete will indicate a cleared

Interrupt Status Register clears upon being read, and requires at least 1 second to be updated. When the

Interrupt Status Register clears, the hardwire interrupt line will also clear until the Registers are updated

by the monitoring loop.

The INT hardware Interrupt output is cleared with the INT_Clear bit, which is Bit 3 of the Configuration

DS1780 monitoring loop will stop. It will resume when the bit is low.

Analog Voltage Limits

The limits for the analog voltage comparison are programmed into the Value RAM at Internal Address

Registers 2Bh - 36h. A high and low limit is associated with each of the 6 analog voltage inputs of the

DS1780. Care must be taken to program the limit registers in the same format as the respective voltage

data register. Please see “OPERATION - Voltage Data Format” for details. For setting a voltage

interrupt, the DS1780 compares on a “greater than” basis for high limits and a “less than or equal to”

basis for low limits. The host can mask any or all of the voltage limits for interrupt contention.

Temperature Limits and Interrupt Modes

The host programs an 8-bit high temperature limit and hysteresis/low temperature limit into the DS1780

at Internal Address Registers 39h and 3 Ah in the same two’s complement format described in the

“OPERATION - Temperature Data Format” section. The temperature mode is programmed into the

Temperature Configuration Register (0x4Bh). A digital 8-bit comparator is also incorporated that

compares the temperature readings to the programmed limits.

There are three interrupt modes of operation. The INT output can be programmed for either of the three

interrupt modes of operation and the host can program the DS1780 to completely mask temperature

interrupts from controlling the INT output.

DS1780

13 of 28

1. One-time Interrupt mode: Exceeding hot temperature limit causes an SMI that will remain active

indefinitely until reset by reading Interrupt Status Register 1 or cleared by the INT_Clear bit in the

Configuration register. Once an SMI event has occurred by crossing the hot temperature limit, then

subsequently reset, an SMI will not occur again until the temperature goes below hot temperature

hysteresis (low) limit.

2. Default Interrupt mode: Exceeding hot temperature limit causes an System Management Interrupt

(SMI) that will remain active indefinitely until reset by reading Interrupt Status Register 1 or cleared

by the INT_Clear bit in the Configuration Register. Once an Interrupt event has occurred by crossing

the Hot Temperature limit, then reset, an Interrupt will occur again once the next temperature

conversion has completed. The interrupts will continue to occur in this manner until the temperature

goes below the hot temperature hysteresis value.

3. Comparator mode: Exceeding hot temperature limit causes the SMI output to go active. SMI will

remain active until the temperature goes below the hot temperature limit. Once the temperature goes

below the hot temperature limit, SMI will become inactive. As in the default and one-time interrupt

modes, the SMI can also be cleared by reading Interrupt Status Register 1 or by setting the INT_Clear

bit in the configuration register.

Figure 4 below illustrates the three temperature interrupt modes.

Fan Speed Limits

The host programs 8-bit fan speed low limits for FAN1 and FAN2 inputs into Internal Address Registers

3Bh and 3Ch, respectively. Care must be taken to program the limit with respect to the divisor chosen for

each of the tachometer inputs. Refer to the “OPERATION - FAN Speed Data Format” section for details.

An interrupt will occur if measured fan speed falls below the programmed limit. Due to the nature of the

algorithm implemented, a count of 255 (max) represents a slow (or stopped) fan; i.e., tachometer counts

are inversely proportional to fan speed. Thus, the fan limit register will contain the maximum number of

counts (or the minimum fan speed) before which an interrupt will occur.

Chassis Intrusion Detection

The CHS input is an active high interrupt from any type of device that detects and captures chassis

intrusion violations. This could be accomplished mechanically, optically, or electrically, and circuitry

external to the DS1780 is expected to latch the event.

The design of the DS1780 allows this input to go high even with no power applied to the DS1780, and no

clamping or other interference with the line will occur. This line can also be pulled low for at least 20 ms

by the DS1780 to reset a typical Chassis Intrusion circuit. Accomplish this reset by setting Bit 6 of

Configuration Register high. The bit in the Register is self-clearing.

A possible chassis intrusion detector/latch is shown below in Figure 5.

DS1780

14 of 28

TEMPERATURE INTERRUPT MODE ILLUSTRATION Figure 4

SAMPLE CHASSIS INTRUSION DETECTOR/LATCH Figure 5

DS1780

15 of 28

OPERATION - Analog Output

The DS1780 has a single analog output from a unsigned 8-bit D/A which produces 0-1.25 volts; this is

amplified and scaled with external circuitry such as a op-amp and transistor to provide fan speed control.

This register is set to 0xFF on power-up, which produces full fan speed. The analog output register (19h)

is unaffected by any reset other than power-on.

This voltage must be scaled and have an output current of at least 250 mA which is needed to drive the

fans; Figure 6 is a simple circuit that can be used, and Table 9 suggest R1 and R2 to select gain.

Although it is recommended to connect the DS1780 analog output to a high impedance node such as that

in Figure 6, the output driver can source 2.0 mA (max) at VOUT = 1.25V while maintaining the error spec

of 5% of FSR over temperature and supply voltage. Stability is guaranteed for a load capacitance up to

100 pF. More capacitance could cause severe overshoots and possible oscillation.

FAN AMPLIFIER CIRCUIT EXAMPLE Figure 6

AMPLIFIER DESIGN EXAMPLES Table 9

Input 1.22

Output 12

Gain 9.84

R1 R2

1,000 9,000

2,200 19,439

3,300 29,159

4,700 41,530

10,000 88,361

OPERATION - NAND TREE Test

A NAND tree is provided in the DS1780 for Automated Test Equipment (ATE) board level connectivity

testing. If the user applies (VDD - 0.5V) to the NTIN input, the device will be in the NAND tree test mode.

A0/NTOUT will become the NAND tree output pin. To perform a NAND tree test all pins included in the

NAND tree (see Figure 7 below) should be driven high.

Beginning with A1 and working around the chip, each pin can be toggled and a resulting toggle can be

observed on A0/NTOUT.

Allow for a typical propagation delay of 100 ns.

DS1780

16 of 28

Note: To properly implement the NAND TREE test on the PCB, no pins listed in the tree should be

connected directly to power or ground; if a pin is needed to configure as a permanent low such as an

address, it should be connected to ground through a low value resister such as 330 (to allow the ATE

(Automatic Test Equipment) to drive it high.

DS1780 NAND TREE TEST FLOW Figure 7

DS1780 REGISTERS AND RAM

INTERNAL ADDRESS REGISTER Table 10.0

BIT NAME R/W DESCRIPTION

<7:0> Address Pointer W Address of RAM and Registers. See the tables below for detail.

ADDRESS POINTER (POWER ON DEFAULT 00h) Table 10.1

REGISTERS AND RAM <A7:A0>

(HEX)

POWER ON VALUE OF REGISTERS:

<7:0> (BINARY)

Configuration Register 40h 0000 1000

Interrupt INT Status Register 1 41h 0000 0000

Interrupt INT Status Register 2 42h 0000 0000

INT Mask Register 1 43h 0000 0000

INT Mask Register 2 44h 0000 0000

Chassis Intrusion Clear Register 46h 0000 0000

VID Register 47h <7:4> = 0101, <3:0> = VID3 - VID0

Serial Address Register 48h 0010 1101

VID 4 Register 49h <7:1> = 1000 000, <0>=VID 4

Temperature Configuration Register 4Bh 0000 0001

Test Register 15h 0000 0000

Analog Output 19h 1111 1111

Value RAM 20h-3Dh

Company ID 3Eh 1101 1010

Stepping 3Fh 0000 0001

DS1780

17 of 28

CONFIGURATION REGISTER (ADDRESS 0X40; POWER-UP DEFAULT = 08h)

Table 10.2

BIT NAME R/W DESCRIPTION

0 START R/W

Logic 1 enables startup of measurement loop, logic 0 places the DS1780 in standby mode.

Caution: The INT output pin will not be cleared if the user writes a 0 to this location after an

interrupt has occurred (see “ INT Clear” bit). At startup, limit checking functions and

scanning begins. Note, all HIGH and LOW LIMITS should be set into the DS1780 prior to

turning on this bit. (Power-up default=0).

1 INT Enable R/W

Logic 1 enables the INT output. 1=Enabled 0=Disabled (Power-up Default = 0)

2 Reserved R/W Power-up Default = 0.

3 INT Clear R/W

During Interrupt Service Routine (ISR) this bit asserted logic 1 clears INT output without

affecting the contents of the Interrupt Status Registers. The device will stop monitoring. It

will resume upon clearing of this bit. (Power-up default=1.)

4 RESET R/W

Creates a RESET (Active Low) signal for 20 ms (min) on the RST output. (Power-up

default = 0) This bit is cleared once the RST pulse goes active.

5 Reserved R/W Power-up Default = 0.

6 CHS Reset R/W

Logic 1 resets the chassis intrusion pin. (Power-up default = 0) This bit is cleared after CHS

becomes cleared.

7 Initialization R/W

Logic 1 restores power-up default values to all DS1780 registers except for the analog

output and value RAM, which remain unchanged. This bit automatically clears itself since

the power on default is 0.

INTERRUPT INT STATUS REGISTER 1 (ADDRESS 0X41; POWER-UP

DEFAULT = 00h) Table 10.3

BIT NAME R/W DESCRIPTION

0 +2.5V_Error R A 1 indicates a High or Low limit has been exceeded.

1 VCCP1_Errror R A 1 indicates a High or Low limit has been exceeded.

2 +3.3V_Error R A 1 indicates a High or Low limit has been exceeded.

3 +5V_Error R A 1 indicates a High or Low limit has been exceeded.

4 Temp_Error R

A 1 indicates that a high or low temperature limit has been exceeded. The conditions that

will generate and clear this bit depend upon the temperature interrupt mode chosen. The

mode is set at bits 0 and 1 of the Temperature Configuration Register (0x48h).

5 Reserved R 0

6 FAN1_Error R A 1 indicates that a fan count limit has been exceeded.

7 FAN2_Error R A 1 indicates that a fan count limit has been exceeded.

DS1780

18 of 28

INTERRUPT INT STATUS REGISTER 2 (ADDRESS 0X42; POWER-UP

DEFAULT=00h) Table 10.4

BIT NAME R/W DESCRIPTION

0 +12V_Error R A 1 indicates a High or Low limit has been exceeded.

1 -12V/

VCCP2_Error R A 1 indicates a High or Low limit has been exceeded.

2 Reserved R 0

3 Reserved R 0

4 Chassis_Error R A 1 indicates Chassis Intrusion has gone high.

5 Reserved R 0

6 Reserved R 0

7 Reserved R 0

Note: Anytime the INT Status Registers are read out, the conditions (i.e., Registers) that are read are

automatically reset to power-up state (except CHS, which can only be cleared by CHS reset). In the case

of the VOLTAGE priority indication, if two or more voltages were out of LIMITS, then another

indication would automatically be generated if it were not handled during the ISR.

The errant voltage may be masked until the operator has time to clear the errant condition or set the limit

higher/lower.

INT MASK REGISTER 1 (ADDRESS 0X43; POWER-UP DEFAULT=00h)

Table 10.5

BIT NAME R/W DESCRIPTION

0 +2.5V R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

1 +VCCP1 R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

2 +3.3V R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

3 +5V R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

4 Temp R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

5 Reserved R/W Power on default = 0.

6 FAN1 R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

7 FAN2 R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

INT MASK REGISTER 2 (ADDRESS 0X44; POWER-UP DEFAULT=00h)

Table 10.6

BIT NAME R/W DESCRIPTION

0 +12V R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

1 -12V/VCCP2 R/W

A 1 disables the corresponding interrupt status bit for INT interrupt.

2 Reserved R/W Power-up Default = 0.

3 Reserved R/W Power-up Default = 0.

CHS_sec

(Chassis

Intrusion)

R/W A 1 disables the corresponding interrupt status bit for INT interrupt.

5 Reserved R/W Power-up Default = 0.

6 Reserved R/W Power-up Default = 0.

7 Reset Enable R/W A 1 enables the RESET in the configuration register.

DS1780

19 of 28

RESERVED REGISTER (ADDRESS 0X45; POWER-UP DEFAULT=00h)

Table 10.7

BIT NAME R/W DESCRIPTION

<7:0> RESERVED R/W Undefined (Power On = 00h).

CHASSIS INTRUSION CLEAR REGISTER (ADDRESS 0X46; POWER-UP

DEFAULT=00h) Table 10.8

BIT NAME R/W DESCRIPTION

0-6 RESERVED R/W Undefined (Power On = 00h).

7 Chassis Int

Clear R/W A 1 outputs a minimum 20 ms active low pulse on the Chassis Intrusion (CHS) pin. The

VID REGISTER (ADDRESS 0x47; POWER-UP DEFAULT = SEE “ADDRESS

POINTER” TABLE) Table 10.9

BIT NAME R/W DESCRIPTION

0-3 VID R

The VID[3:0] inputs from Pentium/PRO power supplies to indicate the operating voltage

(e.g., 1.5V to 2.9V).

4-5 FAN1 RPM

control R/W

FAN1 Speed Control.

<5:4> = 00 - divide by 1

<5:4> = 01 - divide by 2

<5:4> = 10 - divide by 4

<5:4> = 11 - divide by 8

6-7 FAN2 RPM

control R/W

FAN2 Speed Control.

<7:6> = 00 - divide by 1

<7:6> = 01 - divide by 2

<7:6> = 10 - divide by 4

<7:6> = 11 - divide by 8

SERIAL ADDRESS REGISTER (ADDRESS 0x48; POWER-UP DEFAULT =

SEE DESCRIPTION BELOW) Table 10.10

BIT NAME R/W DESCRIPTION

0-7 2-Wire Bus

Address R/W 2-Wire Bus Address (Power On = 001011(A1)(A0)).

VID4 REGISTER (ADDRESS 0x49; POWER-UP DEFAULT = SEE

DESCRIPTION BELOW Table 10.11

BIT NAME R/W DESCRIPTION

0 VID 4 R VID4 Input.

1-7 Reserved R/W Default Power On Values = 1000000.

DS1780

20 of 28

TEMPERATURE CONFIGURATION REGISTER (ADDRESS Ox4B; POWER-UP

DEFAULT = 01h) Table 10.12

BIT NAME R/W DESCRIPTION

Hot

Temperature

Interrupt

mode select

Bit 0

R/W

If Bits 0 and Bits 1 of this register are both 0 or both 1, this selects the default interrupt

mode which gives the user an interrupt if the temperature goes above the hot limit. The

interrupt will be cleared once the status register is read, but it will again be generated when

the next conversion has completed. It will continue to do so until the temperature goes

below the hysteresis limit.

A 0 on Bit 1 and a 1 on Bit 0 selects the one-time interrupt mode which gives the user an

indefinite interrupt when it goes above the hot limit. The interrupt will be cleared once the

status register is read. Another interrupt will not be generated until the temperature first goes

below the hysteresis limit. It will also be cleared if the status register is read. No more

interrupts will be generated until the temperature goes above the hot limit again. The

corresponding bit will be cleared in the status register every time it is read but may not set

again when the next conversion is done.

Hot

Temperature

Interrupt

mode select

Bit 1

R/W

A 1 on this bit (Bit 1) and a 0 on Bit 0 selects the comparator mode. This gives an SMI

when the temperature exceeds the hot limit. This SMI remains active until the status register

is read or the temperature goes below the hot limit (no hysteresis), when the SMI will

become inactive.

2-6 Reserved R/W Default = 00000.

7 Temp [0] R Ninth bit of the temperature (Value = 0.5°C).

TEST REGISTER (ADDRESS 0x15h; POWER-UP DEFAULT = 00h)

Table 10.13

ADDRESS <A7:0A>h R/W DESCRIPTION

15h Note 3 Power-up Default = 00h

ANALOG OUTPUT (ADDRESS 0x19h; POWER-UP DEFAULT = FFh)

Table 10.14

ADDRESS <A7:0A>h R/W DESCRIPTION

19h R/W

Power-up Default = FFh. No other reset affects this register. FFh

value set analog out to MAX value = 1.25V.

DS1780

21 of 28

VALUE RAM (ADDRESS 0x15h - 0x3Dh) Table 10.15

ADDRESS <A7:A0>h R/W DESCRIPTION

20h R +2.5V Input Reading.

21h R VCCP1 Input Reading.

22h R +3.3V Input Reading.

23h R +5V Input Reading.

24h R +12V Input Reading.

25h R +2.5V_Sense/VCCP2 Input Reading.

26h R Reserved.

27h R Temperature reading (Most significant 8-bits).

28h R

FAN1 reading: This location stores the number of counts of the

internal clock per revolution.

29h R

FAN2 reading: This location stores the number of counts of the

internal clock per revolution.

2Ah R/W Reserved.

2Bh R/W +2.5V High Limit (Note 1, 2).

2Ch R/W +2.5V Low Limit (Note 2).

2Dh R/W +VCCP1 High Limit (Note 1, 2).

2Eh R/W +V CCP1 Low Limit (Note 2).

2Fh R/W +3.3V High Limit (Note 1, 2).

30h R/W +3.3V Low Limit (Note 2).

31h R/W +5V High Limit (Note 1, 2).

32h R/W +5V Low Limit (Note 2).

33h R/W +12V High Limit (Note 1, 2).

34h R/W +12V Low Limit (Note 2).

35h R/W +2.5V_Sense/Vccp2 High Limit (Note 1, 2).

36h R/W +2.5V_Sense/Vccp2 Low Limit (Note 2).

37h Reserved.

38h Reserved.

39h R/W Hot Temperature (High) Limit (Note 1).

3Ah R/W Hot Temperature Hysteresis (Low) Limit.

3Bh R/W

FAN1 Fan Count Limit: It is the number of counts of the internal clock for the

Low Limit of the fan speed.

3Ch R/W

FAN2 Fan Count Limit: It is the number of counts of the internal clock for the

Low Limit of the fan speed.

3Dh

Reserved.

3Eh R

Company id number (Note 5).

3Fh R

Stepping id number (Note 6).

NOTES:

1. Setting all 1s to the high limits for voltages and fans (0111 1111 binary for temperature) means

interrupts will never be generated except the case when voltages go below the low limits.

2. For the high limits of the voltages, the device is doing a greater than comparison. For the low limits,

however, it is doing a less than or equal comparison.

3. This register should only be used by the manufacturer for testing of the ASIC. Reading or writing to

this register during normal use may lead to erroneous events.

DS1780

22 of 28

4. This register will latch an 8-bit value into an R-2R D/A to provide a range of 0-1.25 volts; accuracy

can be ±5% or more.

5. This location will contain the company identification number which will be used by software to

determine analog voltage curves; this register is read only.

6. This location will contain the stepping number of the part; this register is read only.

ABSOLUTE MAXIMUM RATINGS*

Voltage on VDD (GNDD-0.3V) to +6.5V

Voltage on any other pin (except Analog Inputs) (GNDD-0.3V) to (VDD + 0.3V)

Voltage at +12VIN pin (GNDD-0.3V) to 18V

Voltage at other Analog input pins (GNDD-0.3V) to 7.0V

Ground Difference (GNDD-GNDA) ±0.3V

Input Current at any Pin (Note 2) ±5 mA

Package Input Current (Note 2) ±20 mA

Operating Temperature -40°C to +125°C

Storage Temperature -65°C to +150°C

ESD Susceptibility (Human Body Model) 2kV

Soldering Temperature (Note 3) 215°C for 60 seconds (Vapor Phase)

220°C for 15 seconds (IR)

* This is a stress rating only and functional operation of the device at these or any other conditions above

those indicated in the operation sections of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods of time may affect reliability.

The Dallas Semiconductor DS1780 is built to the highest quality standards and manufactured for long

term reliability. All Dallas Semiconductor devices are made using the same quality materials and

manufacturing methods. However, the DS1780 is not exposed to environmental stresses, such as burn-in,

that some industrial applications require. For specific reliability information on this product, please

contact the factory in Dallas at (972) 371-4448.

RECOMMENDED DC OPERATING CONDITIONS

(-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Supply Voltage VDD 2.8 5.75 V

Ground Difference ∆GND IGNDD-

GNDAI 0.1 V

Digital

Input Voltage VIND -0.05 VDD+0.05 V

DS1780

23 of 28

DC ELECTRICAL CHARACTERISTICS

Power Supply (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Active ADC and

DAC, Interface

Inactive

0.7 1.0 mA

ADC, DAC and

Interface

Inactive

125 µA

Supply Current IDD

Inactive ADC

and Interface,

DAC Active

250 500 µA

4, 5

DC ELECTRICAL CHARACTERISTICS:

Temperature-to-Digital Converter (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

-40°C£TA

£125°C ±3

Thermometer Error TERR -25°C£TA

£100°C ±2

°C

Resolution 0.5 °C

DC ELECTRICAL CHARACTERISTICS:

Voltage-to-Digital Converter (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

ADC Resolution 8 bits

+2.5VIN Input 13.0

+3.3VIN Input 17.2

+5VIN Input 26.0

+12VIN Input 62.5

+VCCP1,2

Inputs 14.1

Voltage to Digital

Conversion

Resolution

(See Voltage A/D

Section)

+2.5VS Input 64.0

0°C£TA

£100°C ±1.5 % 6

Total Adjusted Error TUE -40°C£TA

£+125°C ±2

Differential

Nonlinearity DNL ±1 LSb

Power Supply

Sensitivity PSS ±1 %/V

Monitoring Cycle tC 0.5 1.0 s 7

Input Resistance RIN 500k 750k Ω

DS1780

24 of 28

DC ELECTRICAL CHARACTERISTICS:

Fan RPM-to-Digital Converter (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

0°C£TA

£100°C ±6

Accuracy

-40°C£TA

£+125°C ±12

Full scale count 255 decimal

Divisor=1; Fan

Count=153 8800

Divisor=2; Fan

Count=153 4400

Divisor=4; Fan

Count=153 2200

FAN1 & FAN2

Normal Input RPM

Divisor=8; Fan

Count=153 1100

RPM 8

Internal Oscillator

Frequency +25°C£TA

£+75°C 21.15 22.5 23.85 kHz

DC ELECTRICAL CHARACTERISTICS:

Analog Output VOUT (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

DAC Resolution 8 bits

Voltage Range 0 1.25 V

Error DACERR ±5

% of

FSR

Output Current IOUT 2.0 mA

Load Capacitance CLOAD 100 pF

DC ELECTRICAL CHARACTERISTICS:

Digital Outputs: A0NTOUT (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

IOUT=±5 mA at

VDD=4.25V

Logical “1”

Output Voltage VOUT(1) IOUT=±3 mA at

VDD=2.85V

2.4

IOUT=±5 mA at

VDD=5.75V

Logical “0”

Output Voltage VOUT(0) IOUT=±3 mA at

VDD=3.45V

0.4 V

DS1780

25 of 28

DC ELECTRICAL CHARACTERISTICS:

Open-drain Digital Outputs: RST , CHS, INT

(-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

IOUT=±5 mA at

VDD=5.75V

Logical 0

Output Voltage VOUT(0) IOUT=±3 mA at

VDD=3.45V

0.4

High Level

Output Current IOH V

OUT=VDD 0.1 100 µA

Active Pulse Width RST and CHS 20 45 ms

DC ELECTRICAL CHARACTERISTICS:

Open-drain 2-Wire Bus Output: SDA (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

IOUT=±5 mA at

VDD=5.75V

Logical 0

Output Voltage VOUT(0) IOUT=±3 mA at

VDD=3.45V

0.4

High Level

Output Current IOH V

OUT=VDD 0.1 100 µA

DC ELECTRICAL CHARACTERISTICS:

2-Wire Bus Digital Inputs: SDA, SCL (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Logical 1

Input Voltage VIN(1)

0.7VDD V

Logical 0

Input Voltage VIN(0) 0.3VDD V

DC ELECTRICAL CHARACTERISTICS:

Digital Inputs: A0/NTOUT, A1, CHS, VID0-4, FAN1, FAN2

(-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Logical 1

Input Voltage VIN(1) VDD=5.0V 2.4 V

Logical 0

Input Voltage VIN(0) VDD=5.0V 0.8 V

Logical 1

Input Voltage VIN(1) VDD=3.3V 2.0 V

Logical 0

Input Voltage VIN(0) VDD=3.3V 0.4 V

DS1780

26 of 28

DC ELECTRICAL CHARACTERISTICS:

All Digital Inputs (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

Logical 1

Input Current IIN(1) VIN=VDD -1

-0.005 µA

Logical 0

Input Current IIN(0) VIN=0V 0.005 1 µA

Input Capacitance CIN

20 pF

AC ELECTRICAL CHARACTERISTICS:

2-Wire Interface (-40°C to +125°C, 2.8V £ VDD £ 5.75V)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES

SCL Clock Period t1 2.5 µs

Data In Setup

Time to SCL High t2 100 ns

Data Out Stable

after SCL Low t3 0 ns

SDA Low Setup

Time to SCL Low

(START)

t4 100 ns

SDA High Hold

Time after SCL

High (STOP)

t5 100 ns

DS1780

27 of 28

2-WIRE BUS TIMING DIAGRAM Figure 8

NOTES:

1. All voltages are referenced to ground, unless otherwise specified.

When the input voltage (VIN) at any pin exceeds the power supplies (VIN< (GND or GNDA) or VIN

>VDD, except for analog voltage inputs), the current at that pin should be limited to 5 mA. The 20 mA

maximum package input current rating limits the number of pins that can safely exceed the power

supplies with an input current of 5 mA to four.

2. Solder according to IPC standards.

3. IDD specified with open-drain output pin open.

4. IDD specified with VCC at 5.0V and SDA, SCL = 5.0V.

5. TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC.

6. Monitoring Cycle Time includes temperature conversion, voltage conversions, and fan speed

readings.

7. The total fan count is based on 2 pulses per revolution of the fan tachometer output.

8. Limits (Min and Max specs) are defined for the full temperature range -40°C £ T

A £ +125°C and

voltage range 2.8V £ VDD £ 5.75V, unless otherwise stated as a condition. Typical values represent

parametric norms at TA = 25°C at 4.5V £ VDD £ 5.5V, unless otherwise stated as a condition.

ORDERING INFORMATION Table 11

ORDERING

NUMBER

PACKAGE

MARKING DESCRIPTION

DS1780E+ DS1780 (See Note) DS1780 in Lead-Free 24-pin TSSOP

DS1780E+T&R DS1780 (See Note) DS1780 in Lead-Free 24-pin TSSOP, 1000 Piece Tape-and-

Reel

DS1780E DS1780 DS1780 in 24-pin TSSOP

DS1780E/T&R DS1780 DS1780 in 24-pin TSSOP, 1000 Piece Tape-and-Reel

Note: A "+" symbol will also be marked on the package near the Pin 1 indicator

DS1780

28 of 28

DS1780 24 LD. TSSOP

DIM MIN MAX

A - 1.10

A1 0.05 -

A2 0.75 1.05

c 0.09 0.18

phi 0° 8°

L 0.50 0.70

e1 0.65 BSC

B 0.18 0.30

D 7.55 8.00

E 4.40 NOM

G 0.25 REF

H 6.25 6.55

OTES:

1. DIMENSION “D” INCLUDES MOLD

MISSMATCH, FLASH, AND PROTRUSIONS.