ADM1027 datasheet(16/56 Pages) AD

16 / 56 page

REV. A

–16–

ADM1027

TEMPERATURE MEASUREMENT REGISTERS

Reg. 0x25 Remote 1 Temperature = 0x80 default

Reg. 0x26 Local Temperature = 0x80 default

Reg. 0x27 Remote 2 Temperature = 0x80 default

Reg. 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 MEASUREMENT 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.

Reg. 0x4E Remote 1 Temperature Low Limit = 0x81 default

Reg. 0x4F Remote 1 Temperature High Limit = 0x7F default

Reg. 0x50 Local Temperature Low Limit = 0x81 default

Reg. 0x51 Local Temperature High Limit = 0x7F default

Reg. 0x52 Remote 2 Temperature Low Limit = 0x81 default

Reg. 0x53 Remote 2 Temperature High Limit = 0x7F default

READING TEMPERATURE FROM THE ADM1027

It is important to note that temperature can be read from the

ADM1027 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. The extended resolution register

(Reg. 0x77) should be read first. This causes all temperature

reading registers to be frozen until all temperature reading regis-

ters 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

A number of other functions are available on the ADM1027 to

offer the systems 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. There may

be an instance where the user would like to take a very fast

measurement, e.g., of CPU temperature. Setting Bit 4 of Con-

figuration Register 2 (Reg. 0x73) turns averaging off. This takes

a reading every 13 ms. The measurement itself takes 4 ms.

Single-Channel ADC Conversions

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

ADM1027 into single-channel ADC conversion mode. In this

mode, the ADM1027 can be made to read a single temperature

channel only. If the internal ADM1027 clock is used, the selected

input will be read every 1.4 ms. The appropriate ADC channel

is selected by writing to Bits <7:5> of TACH1 minimum high

byte register (Reg. 0x55).

Bits <7:5> Reg 0x55

Channel Selected

101

Remote 1 Temp

110

Local Temp

111

Remote 2 Temp

Configuration Register 2 (Reg. 0x73)

<4> = 1

Averaging off

<6> = 1

Single-channel convert mode

TACH1 Minimum High Byte (Reg. 0x55)

<7:5>

Selects ADC channel for single-channel convert mode

OVERTEMPERATURE EVENTS

Overtemperature events on any of the temperature channels can

be detected and dealt with automatically. Registers 0x6A to

0x6C are the THERM limits. When a temperature exceeds its

THERM limit, all fans will run at 100% duty cycle. The fans

will stay running at 100% until the temperature drops below

THERM – 4

∞C.

FANS

THERM LIMIT

TEMP

100%

HYSTERESIS = 4 C

Figure 15. THERM Limit Operation

ADM1027 Datasheet(PDF) 16 Page - Analog Devices

ADM1027 Datasheet(HTML) 16 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

Datasheet Download

Link URL