ADT7476AARQZ データシートの表示（PDF） - ON Semiconductor

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ADT7476AARQZ

dBCOOL® Remote Thermal Controller and Voltage Monitor

ON Semiconductor 

ADT7476A

The ADT7476A has temperature offset registers (0x70

and 0x72) for the Remote 1 and Remote 2 temperature

channels. By doing a one-time calibration of the system, the

user can determine the offset caused by system board noise

and null it out using the offset registers. The offset registers

automatically add a twos complement 8-bit reading to every

temperature measurement.

Changing Bit 1 of Configuration Register 5 (0x7C)

changes the resolution and therefore, the range of the

temperature offset as either having a −63°C to +127°C range

with a resolution of 1°C or having a −63°C to +64°C range

with a resolution of 0.5°C. This temperature offset can be

used to compensate for linear temperature errors introduced

by noise.

Temperature Offset Registers

Register 0x70, Remote 1 Temperature Offset = 0x00 (0°C

default)

Register 0x71, Local Temperature Offset = 0x00 (0°C default)

Register 0x72, Remote 2 Temperature Offset = 0x00 (0°C

default)

ADT7463/ADT7476A Backwards Compatible Mode

By setting Bit 0 of Configuration Register 5 (0x7C), all

temperature measurements are stored in the zone

temperature reading registers (0x25, 0x26, and 0x27) in

twos complement in the −63°C to +127°C range. The

temperature limits must be reprogrammed in twos

complement.

If a twos complement temperature below −63°C is

entered, the temperature is clamped to −63°C. In this mode,

the diode fault condition remains −128°C = 1000 0000,

while in the extended temperature range (−63°C to +191°C),

the fault condition is represented by −64°C = 0000 0000.

Temperature Reading Registers

Register 0x25, Remote 1 Temperature

Register 0x26, Local Temperature

Register 0x27, Remote 2 Temperature

Register 0x77, Extended Resolution 2 = 0x00 default

[7:6] TDM2, Remote 2 temperature LSBs.

[5:4] LTMP, Local temperature LSBs.

[3:2] TDM1, Remote 1 temperature LSBs.

Temperature Limit Registers

Associated with each temperature measurement channel

are high and low limit registers. Exceeding the programmed

high or low limit causes the appropriate status bit to be set.

Exceeding either limit can also generate SMBALERT

interrupts (depending on the way the interrupt mask register

is programmed and assuming that SMBALERT is set as an

output on the appropriate pin).

Register 0x4E, Remote 1 Temperature Low Limit = 0x81 default

Register 0x4F, Remote 1 Temperature High Limit = 0x7F

default

Register 0x50, Local Temperature Low Limit = 0x81 default

Register 0x51, Local Temperature High Limit = 0x7F default

Register 0x52, Remote 2 Temperature Low Limit = 0x81 default

Register 0x53, Remote 2 Temperature High Limit = 0x7F

default

Reading Temperature from the ADT7476A

It is important to note that temperature can be read from

the ADT7476A as an 8-bit value (with 1°C resolution) or as

a 10-bit value (with 0.25°C resolution). If only 1°C

resolution is required, the temperature readings can be read

back at any time and in no particular order.

If the 10-bit measurement is required, this involves a

2-register read for each measurement. Extended Resolution

Register 2 (0x77) should be read first. This causes all

temperature reading registers to be frozen until all

temperature reading registers have been read from. This

prevents an MSB reading from being updated while its two

LSBs are being read and vice versa.

Additional ADC Functions for Temperature

Measurement

A number of other functions are available on the

ADT7476A to offer the system designer increased

flexibility.

Turn-Off Averaging

For each temperature measurement read from a value

register, 16 readings have actually been made internally, and

the results averaged, before being placed into the value

register. Sometimes it is necessary to take a very fast

measurement. Setting Bit 4 of Configuration Register 2

(0x73) turns averaging off. The default round robin cycle

time takes 146.5 ms.

Table 8. Conversion Time with Averaging Disabled

Channel

Voltage Channels

Remote Temperature 1

Remote Temperature 2

Local Temperature

Measurement Time (ms)

0.7

7

7

1.3

When Bit 7 of Configuration Register 6 (0x10) is set, the

default round robin cycle time increases to 240 ms.

Table 9. Conversion Time with Averaging Enabled

Channel

Voltage Channels

Remote Temperature

Local Temperature

Measurement Time (ms)

11

39

12

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