ADT7461ARM-REEL データシートの表示（PDF） - ON Semiconductor

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ADT7461ARM-REEL

±1°C Temperature Monitor with Series Resistance Cancellation

ON Semiconductor 

ADT7461

When Pin 6 is configured as THERM2, only the high

temperature limits are relevant. If Flag 6 and/or Flag 4 are

set, the THERM2 output goes low to indicate the

temperature measurements are outside the programmed

limits. Flag 5 and Flag 3 have no effect on THERM2. The

behavior of THERM2 is otherwise the same as THERM.

Table 5. Status Register Bit Assignments

Bit

Name

Function

7

BUSY 1 when ADC is converting

(Note 1)

6

LHIGH 1 when local high temperature limit is

(Note 2) tripped

5

LLOW 1 when local low temperature limit is

(Note 2) tripped

4

RHIGH 1 when remote high temperature limit is

(Note 2) tripped

3

RLOW 1 when remote low temperature limit is

(Note 2) tripped

2

OPEN 1 when remote sensor is an open circuit

(Note 2)

1

RTHRM 1 when remote THERM limit is tripped

0

LTHRM 1 when local THERM limit is tripped

1. Polling of the BUSY bit is not recommended.

2. These flags stay high until the status register is read or they

are reset by POR.

Offset Register

Offset errors may be introduced into the remote

temperature measurement by clock noise or by the thermal

diode being located away from the hot spot. To achieve the

specified accuracy on this channel, these offsets must be

removed.

The offset value is stored as a 10-bit, twos complement

value in Registers 0x11 (high byte) and 0x12 (low byte, left

justified). Only the upper 2 bits of Register 0x12 are used.

The MSB of Register 0x11 is the sign bit. The minimum

offset that can be programmed is −128°C, and the maximum

is +127.75°C. The value in the offset register is added to the

measured value of the remote temperature.

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

and has no effect unless the user writes a different value to it.

Table 6. Sample Offset Register Codes

Offset Value

0x11

0x12

−128°C

−4°C

−1°C

−0.25°C

0°C

+0.25°C

+1°C

+4°C

+127.75°C

1000 0000

1111 1100

1111 1111

1111 1111

0000 0000

0000 0000

0000 0001

0000 0100

0111 1111

00 00 0000

00 00 0000

00 000000

10 00 0000

00 00 0000

01 00 0000

00 00 0000

00 00 0000

11 00 0000

One-Shot Register

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

comparison cycle when the ADT7461 is in standby mode,

after which the device returns to standby. Writing to the

one-shot register address (0x0F) causes the ADT7461 to

perform a conversion and comparison on both the internal

and the external temperature channels. This is not a data

register as such; the write operation to Address 0x0F causes

the one-shot conversion. The data written to this address is

irrelevant and is not stored.

Consecutive ALERT Register

The value written to this register determines how many

out-of-limit measurements must occur before an ALERT is

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

measurement generates an ALERT. The maximum value that

can be chosen is 4. The purpose of this register is to allow the

user to perform some filtering of the output. This is

particularly useful at the fastest three conversion rates, where

no averaging takes place. This register is at Address 0x22.

Table 7. Consecutive ALERT Register Codes

Register Value

Number of Out−of−Limit

Measurements Required

yxxx 000x

1

yxxx 001x

2

yxxx 011x

3

yxxx 111x

4

NOTE: x = don’t care bits, and y = SMBus timeout bit.

Default = 0. See SMBus section for more information.

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