adm1027 Analog Devices, Inc., adm1027 Datasheet - Page 16

• Manufacturer Part Number: adm1027
• Description: Dbcool? Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

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.
–16–
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
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.
THERM LIMIT
FANS
101
110
111
TEMP
Figure 15. THERM Limit Operation
100%
Channel Selected
Remote 1 Temp
Local Temp
Remote 2 Temp
HYSTERESIS = 4 C
REV. A