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ADT7476

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used to compensate for linear temperature errors introduced

by noise.

Temperature Offset Registers

°C default)

ADT7463/ADT7476 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

[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).

Reading Temperature from the ADT7476

It is important to note that temperature can be read from

the ADT7476 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

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

ADT7476 to offer the system designer increased flexibility.

Turn−Off Averaging

For each temperature measurement read from a value

the results averaged, before being placed into the value

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

Measurement Time (ms)

Voltage Channels

0.7

Remote Temperature 1

Remote Temperature 2

Local Temperature

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

Measurement Time (ms)

Voltage Channels

Remote Temperature

Local Temperature

Single−Channel ADC Conversions

Setting Bit 6 of Configuration Register 2 (0x73) places the

ADT7476 into single−channel ADC conversion mode. In

this mode, the ADT7476 can be made to read a single

temperature channel only. The appropriate ADC channel is

selected by writing to Bits [7:5] of the TACH1 minimum

high byte register (0x55).

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