ADM1032ARMZ-1RL Datasheet ADM1032ARZ-001, ADM1032ARMZ-002, ADM1032ARMZ-REEL | P7-P9

ADM1032

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Functional Description

The ADM1032 is a local and remote temperature sensor

and overtemperature alarm. When the ADM1032 is

operating normally, the on-board A/D converter operates in

a free running mode. The analog input multiplexer

alternately selects either the on-chip temperature sensor to

measure its local temperature or the remote temperature

sensor. These signals are digitized by the ADC, and the

results are stored in the local and remote temperature value

registers.

The measurement results are compared with local and

remote, high, low, and THERM

temperature limits stored in

nine on-chip registers. Out-of-limit comparisons generate

flags that are stored in the status register, and one or more

out-of-limit results cause the ALERT

output to pull low.

Exceeding THERM

temperature limits causes the THERM

output to assert low.

The limit registers can be programmed, and the device

controlled and configured, via the serial SMBus. The

contents of any register can also be read back via the SMBus.

Control and configuration functions consist of:

• Switching the Device between Normal Operation and

Standby Mode

• Masking or Enabling the ALERT Output

• Selecting the Conversion Rate

Measurement Method

A simple method of measuring temperature is to exploit

the negative temperature coefficient of a diode, or the

base-emitter voltage of a transistor, operated at constant

current. Unfortunately, this technique requires calibration to

null out the effect of the absolute value of V

, which varies

from device to device.

The technique used in the ADM1032 is to measure the

change in V

when the device is operated at two different

currents.

This is given by:

(eq. 1)

(

)

where:

K is Boltzmann’s constant (1.38 × 10

–23

)

q is the charge on the electron (1.6 × 10

–19

Coulombs)

T is the absolute temperature in Kelvins

N is the ratio of the two currents

is the ideality factor of the thermal diode.

The ADM1032 is trimmed for an ideality factor of 1.008.

Figure 12 shows the input signal conditioning used to

measure the output of an external temperature sensor.

Figure 12 shows the external sensor as a substrate transistor,

provided for temperature monitoring on some

microprocessors, but it could equally well be a discrete

transistor. If a discrete transistor is used, the collector is not

grounded and should be linked to the base. To prevent

ground noise interfering with the measurement, the more

negative terminal of the sensor is not referenced to ground

but is biased above ground by an internal diode at the D−

input. If the sensor is operating in a noisy environment, C1

can optionally be added as a noise filter. Its value should be

no more than 1000 pF. See the Layout Considerations

section for more information on C1.

To measure DV

, the sensor is switched between the

operating currents of I and N × I. The resulting waveform is

passed through a 65 kHz low-pass filter to remove noise, and

then to a chopper-stabilized amplifier that performs the

functions of amplification and rectification of the waveform

to produce a dc voltage proportional to DV

. This voltage

is measured by the ADC to give a temperature output in twos

complement format. To further reduce the effects of noise,

digital filtering is performed by averaging the results of 16

measurement cycles.

Signal conditioning and measurement of the internal

temperature sensor is performed in a similar manner.

Figure 12. Input Signal Conditioning

LOW-PASS FILTER

= 65 kHz

REMOTE

SENSING

TRANSISTOR

BIAS

DIODE

D+

D−

BIAS

IN × I

OUT+

OUT−

To ADC

C1*

* CAPACITOR C1 IS OPTIONAL AND IT SHOULD ONLY BE USED IN VERY NOISY ENVIRONMENTS. C1 = 1000 pF Max.

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Temperature Data Format

One LSB of the ADC corresponds to 0.125°C, so the ADC

can measure from 0°C to 127.875°C. The temperature data

format is shown in Table 5 and Table 6.

The results of the local and remote temperature

measurements are stored in the local and remote temperature

value registers and are compared with limits programmed

into the local and remote high and low limit registers.

Table 5. TEMPERATURE DATA FORMAT

(LOCAL TEMPERATURE AND REMOTE

TEMPERATURE HIGH BYTE)

Temperature Digital Output

0°C 0 000 0000

1°C 0 000 0001

10°C 0 000 1010

25°C 0 001 1001

50°C 0 011 0010

75°C 0 100 1011

100°C 0 110 0100

125°C 0 111 1101

127°C 0 111 1111

Table 6. EXTENDED TEMPERATURE RESOLUTION

(REMOTE TEMPERATURE LOW BYTE)

Extended Resolution

Remote Temperature

Low Byte

0.000°C 0 000 0000

0.125°C 0 010 0000

0.250°C 0 100 0000

0.375°C 0 110 0000

0.500°C 1 000 0000

0.625°C 1 010 0000

0.750°C 1 100 0000

0.875°C 1 110 0000

ADM1032 Registers

The ADM1032 contains registers that are used to store the

results of remote and local temperature measurements and

high and low temperature limits and to configure and control

the device. A description of these registers follows, and

further details are given in Table 7 to Table 11.

Address Pointer Register

The address pointer register itself does not have, or

require, an address because it is the register the first data byte

of every write operation is written to automatically. This

data byte is an address pointer that sets up one of the other

registers for the second byte of the write operation or for a

subsequent read operation.

The power-on default value of the address pointer register

is 00h. Therefore, if a read operation is performed

immediately after power-on without first writing to the

address pointer, the value of the local temperature is returned

because its register address is 00h.

Value Registers

The ADM1032 has three registers to store the results of

local and remote temperature measurements. These

registers are written to by the ADC only and can be read over

the SMBus.

Offset Register

Series resistance on the D+ and D− lines in processor

packages and clock noise can introduce offset errors into the

remote temperature measurement. To achieve the specified

accuracy on this channel, these offsets must be removed.

The offset value is stored as an 11-bit, twos complement

value in Register 11h (high byte) and Register 12h (low

byte, left justified). The value of the offset is negative if the

MSB of Register 11h is 1 and positive if the MSB of

of the remote temperature.

The offset register powers up with a default value of 0°C

and has no effect if nothing is written to them.

Table 7. SAMPLE OFFSET REGISTER CODES

Offset Value 11h 12h

−4°C 1 111 1100 0 000 0000

−1°C 1 111 1111 0 000 0000

−0.125°C 1 111 1111 1 110 0000

0°C 0 000 0000 0 000 0000

+0.125°C 0 000 0000 0 010 0000

+1°C 0 000 0001 0 000 0000

+4°C 0 000 0100 0 000 0000

Status Register

Bit 7 of the status register indicates that the ADC is busy

converting when it is high. Bit 6 to Bit 3, Bit 1, and Bit 0 are

flags that indicate the results of the limit comparisons. Bit 2

is set when the remote sensor is open circuit.

If the local and/or remote temperature measurement is

above the corresponding high temperature limit, or below or

equal to the corresponding low temperature limit, one or

more of these flags is set. These five flags (Bit 6 to Bit 2) are

NOR’ed together, so that if any of them are high, the ALERT

interrupt latch is set and the ALERT output goes low.

Reading the status register clears the five flag bits, provided

that the error conditions that caused the flags to be set have

gone away. While a limit comparator is tripped due to a value

sensor is open circuit, the corresponding flag bit cannot be

reset. A flag bit can only be reset if the corresponding value

good.

The ALERT

interrupt latch is not reset by reading the

status register but is reset when the ALERT

output is

serviced by the master reading the device address, provided

the error condition has gone away and the status register flag

bits are reset.

When Flag 1 and Flag 0 are set, the THERM

output goes

low to indicate that the temperature measurements are

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outside the programmed limits. THERM output does not

need to be reset, unlike the ALERT

output. Once the

measurements are within the limits, the corresponding status

output goes high.

Table 8. STATUS REGISTER BIT ASSIGNMENTS

Bit Name Function

7 BUSY 1 When ADC Converting

6 LHIGH

(Note 1)

1 When Local High Temp Limit Tripped

5 LLOW

(Note 1)

1 When Local Low Temp Limit Tripped

4 RHIGH

(Note 1)

1 When Remote High Temp Limit

Tripped

3 RLOW

(Note 1)

1 When Remote Low Temp Limit

Tripped

2 OPEN

(Note 1)

1 When Remote Sensor Open-Circuit

1 RTHRM 1 When Remote THERM Limit Tripped

0 LTHRM1 1 When Local THERM Limit Tripped

1. These flags stay high until the status register is read, or they are

reset by POR.

Configuration Register

Two bits of the configuration register are used. If Bit 6 is

0, which is the power-on default, the device is in operating

mode with the ADC converting. If Bit 6 is set to 1, the device

is in standby mode and the ADC does not convert. The

SMBus does, however, remain active in standby mode so

values can be read from or written to the SMBus. The

ALERT

and THERM O/Ps are also active in standby mode.

Bit 7 of the configuration register is used to mask the alert

output. If Bit 7 is 0, which is the power-on default, the output

is enabled. If Bit 7 is set to 1, the output is disabled.

Table 9. CONFIGURATION REGISTER BIT

ASSIGNMENTS

Bit Name Function

Power-On

Default

7 MASK1 0 = ALERT Enabled

1 = ALERT

Masked

6 RUN/STOP 0 = Run

1 = Standby

5 to 0 Reserved 0

Conversion Rate Register

The lowest four bits of this register are used to program the

conversion rate by dividing the internal oscillator clock by

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, or 1024 to give

conversion times from 15.5 ms (Code 0Ah) to 16 seconds

(Code 00h). This register can be written to and read back

over the SMBus. The higher four bits of this register are

unused and must be set to 0. Use of slower conversion times

greatly reduces the device power consumption, as shown in

Table 10.

Table 10. CONVERSION RATE REGISTER CODES

Data Conversion/Sec Average Supply Current

mA Typ at V

= 5.5 V

00h 0.0625 0.17

01h 0.125 0.20

02h 0.25 0.21

03h 0.5 0.24

04h 1 0.29

05h 2 0.40

06h 4 0.61

07h 8 1.1

08h 16 1.9

09h 32 0.73

0Ah 64 1.23

0B to FFh Reserved

Limit Registers

The ADM1032 has nine limit registers to store local and

remote, high, low, and THERM

temperature limits. These

registers can be written to and read back over the SMBus.

The high limit registers perform a > comparison, while the

low limit registers perform a < or = to comparison. For

example, if the high limit register is programmed with 80°C,

measuring 81°C results in an alarm condition. If the low

limit register is programmed with 0°C, measuring 0°C or

lower results in an alarm condition. Exceeding either the

local or remote THERM

limit asserts THERM low. A

default hysteresis value of 10°C is provided, which applies

to both channels. This hysteresis can be reprogrammed to

any value after powerup (Reg 0x21h).

One-Shot Register

The one-shot register is used to initiate a single conversion

and comparison cycle when the ADM1032 is in standby

mode, after which the device returns to standby. This is not

a data register as such, and it is the write operation that

causes the one-shot conversion. The data written to this

address is irrelevant and is not stored. The conversion time

on a single shot is 96 ms when the conversion rate is 16

conversions per second or less. At 32 conversions per

second, the conversion time is 15.3 ms. This is because

averaging is disabled at the faster conversion rates (32 and

64 conversions per second).

Consecutive ALERT Register

This value written to this register determines how many

out-of limit measurements must occur before an ALERT

generated. The default value is that one out-of-limit

measurement generates an ALERT

. The maximum value

that can be chosen is four. The purpose of this register is to

allow the user to perform some filtering of the output. This

is particularly useful at the faster two conversion rates where

no averaging takes place.

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Board Mount Temperature Sensors 1C TDM USOIC8 100C THRMIC

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