ADT7483A(2012) Ver la hoja de datos (PDF) - ON Semiconductor
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ADT7483A Datasheet PDF : 20 Pages
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ADT7483A
Conversion Rate/Channel Selector Register
The conversion rate/channel selector register is at
Address 0x04 for reads, and Address 0x0A for writes. The
four LSBs of this register are used to program the conversion
times from 15.5 ms (Code 0x0A) to 16 seconds
(Code 0x00). To program the ADT7483A to perform
continuous measurements, set the conversion rate register to
0x0B. For example, a conversion rate of 8 conversions/
second means that beginning at 125 ms intervals, the device
performs a conversion on the local and the remote
temperature channels.
This register can be written to and read back over the
SMBus. The default value of this register is 0x07, giving a
rate of 8 conversions/second.
Bit 7 in this register can be used to disable averaging of the
temperature measurements. The ADT7483A can be
configured to take temperature measurements of either a
single temperature channel or all temperature channels.
Bit 5 and Bit 4 can be used to specify which temperature
channel or channels are measured.
Table 11. CONVERSION RATE/CHANNEL SELECTOR REGISTER
Bit
Mnemonic
Function
7
Averaging
Setting this bit to 1 disables averaging of the temperature measurements at the slower conversion
rates (averaging cannot take place at the three faster rates, so setting this bit has no effect). When
default = 0, averaging is enabled.
6
Reserved
Reserved for future use. Do not write to this bit.
<5:4>
Channel Selector
These bits are used to select the temperature measurement channels:
00 = Round Robin = Default = All Channels
01 = Local Temperature
10 = Remote 1 Temperature
11 = Remote 2 Temperature
<3:0>
Conversion Rates
These bits set how often the ADT7483A measures each temperature channel.
Conversions/second
Time
0000 = 0.0625
0001 = 0.125
0010 = 0.25
0011 = 0.5
0100 = 1
0101 = 2
0110 = 4
0111 = 8 = Default
1000 = 16
1001 = 32
1010 = Continuous Measurements
16 s
8s
4s
2s
1s
500 ms
250 ms
125 ms
62.5 ms
31.25 ms
Limit Registers
The ADT7483A has three limits for each temperature
channel: high, low, and THERM temperature limits for
local, Remote 1, and Remote 2 temperature measurements.
The remote temperature high and low limits span two
registers each to contain an upper and lower byte for each
limit. There is also a THERM hysteresis register. All limit
registers can be written to and read back over the SMBus.
See Table 16 for details of the limit registers’ addresses and
their power-on default values.
When Pin 13 is configured as an ALERT output, the high
limit registers perform a > comparison while the low limit
registers perform a comparison. For example, if the high
limit register is programmed with 80C, then measuring
81C will result in an out-of-limit condition, setting a flag in
the status register. If the low limit register is programmed
with 0C, measuring 0C or lower will result in an
out-of-limit condition.
Exceeding either the local or remote THERM limit asserts
THERM low. When Pin 13 is configured as THERM2,
exceeding either the local limit or remote high limit asserts
THERM2 low. A default hysteresis value of 10C is
provided that applies to both THERM channels. This
hysteresis value may be reprogrammed to any value after
power-up using Register Address 0x21.
It is important to remember that the data format for
temperature limits is the same as the temperature
measurement data format. Thus, if the temperature
measurement uses the default (binary), then the temperature
limits also use the binary scale. If the temperature
measurement scale is switched, however, the temperature
limits do not automatically switch. The user must reprogram
the limit registers to the desired value in the correct data
format. For example, if the remote low limit is set at 10C
and the default binary scale is being used, the limit register
value should be 0000 1010b. If the scale is switched to offset
binary, the value in the low temperature limit register should
be reprogrammed to be 0100 1010b.
Status Registers
The status registers are read-only registers, at
Address 0x02 (Status Register 1) and Address 0x23 (Status
Register 2). They contain status information for the
ADT7483A.
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