ADT7475ARQZ(2011) 查看數據表（PDF） - ON Semiconductor
零件编号
产品描述 (功能)
生产厂家
ADT7475ARQZ Datasheet PDF : 58 Pages
| |||
ADT7475
Nulling Out Temperature Errors
As CPUs run faster, it is more difficult to avoid high
frequency clocks when routing the D+/D– traces around a
system board. Even when recommended layout guidelines
are followed, some temperature errors can still be
attributable to noise coupled onto the D+/D– lines. Constant
high frequency noise usually attenuates, or increases,
temperature measurements by a linear, constant value.
The ADT7475 has two temperature offset registers, Register
0x70 and Register 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 range of –63°C to
+127°C, with a resolution of 1°C, or having a range of −63°C
to +64°C, 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/ADT7475 Backwards Compatible Mode
By setting Bit 0 of Configuration Register 5 (0x7C), all
temperature measurements are stored in the zone temperature
value registers (0x25, 0x26, and 0x27) in twos complement
in the range −128°C to +127°C. The temperature limits must
be reprogrammed in twos complement.
If a twos complement temperature below −128°C is
entered, the temperature is clamped to −128°C. In this mode,
the diode fault condition remains −128°C = 1000 0000, while
in the extended temperature range (−64°C to +191°C), the
fault condition is represented by −64°C = 0000 0000.
Temperature Measurement Registers
Register 0x25, Remote 1 Temperature
Register 0x26, Local Temperature
Register 0x27, Remote 2 Temperature
Register 0x77, Extended Resolution 2 = 0x00 default
Bits [7:6] TDM2, Remote 2 Temperature LSBs.
Bits [5:4] LTMP, Local Temperature LSBs.
Bits [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 (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 ADT7475
It is important to note that temperature can be read from
the ADT7475 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
two−register read for each measurement. The 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
ADT7475 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 5. 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.
http://onsemi.com
15
Share Link: 