ADT7316ARQZ1 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
ADT7316ARQZ1
Analog Devices
ADT7316ARQZ1 Datasheet PDF : 44 Pages
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ADT7316/ADT7317/ADT7318
FUNCTIONAL DESCRIPTION—MEASUREMENT
TEMPERATURE SENSOR
The ADT7316/ADT7317/ADT7318 contain an ADC with spe-
cial input signal conditioning to enable operation with external
and on-chip diode temperature sensors. When the ADT7316/
ADT7317/ADT7318 are operating in single-channel mode, the
ADC continually processes the measurement taken on one
channel only. This channel is preselected by Bit C0 and Bit C1
in the Control Configuration 2 register (Address 0x19). When
in round robin mode, the analog input multiplexer sequentially
selects the VDD input channel, the on-chip temperature sensor
to measure its internal temperature, and the external tempera-
ture sensor. These signals are digitized by the ADC and the
results stored in the various value registers.
The measured results are compared with the internal and
external, THIGH and TLOW, limits. These temperature limits are
stored in on-chip registers. If the temperature limits are not
masked out, any out-of-limit comparisons generate flags that
are stored in the Interrupt Status 1 register (Address 0x00). One
or more out-of-limit results cause the INT/INT output to pull
either high or low depending on the output polarity setting.
Theoretically, the temperature measuring circuit can measure
temperatures from −128°C to +127°C with a resolution of 0.25°C.
Temperatures outside TA, however, are outside the guaranteed
operating temperature range of the device. Temperature meas-
urement from −128°C to +127°C is possible using an external
sensor.
Temperature measurement is initiated by three methods. The first
method is applicable when the part is in single-channel meas-
urement mode. The temperature is measured 16 times and
internally averaged to reduce noise. In single-channel mode,
the part continuously monitors the selected channel, that is, as
soon as one measurement is taken, then another one is started
on the same channel. The total time to measure a temperature
channel with the ADC operating at slow speed is typically
11.4 ms (712 μs × 16) for the internal temperature sensor, and
24.22 ms (1.51 ms × 16) for the external temperature sensor.
The new temperature value is stored in two 8-bit registers and
ready for reading by the I2C or SPI interface. The user can
disable the averaging by setting Bit 5 = 1 in the Control Con-
figuration 2 register (Address 0x19). The ADT7316/ADT7317/
ADT7318 default on power-up, with the averaging enabled.
The second temperature measurement method is applicable
when the part is in round robin measurement mode. The part
measures both the internal and external temperature sensors
as it cycles through all possible measurement channels. The
two temperature channels are measured each time the part
runs a round robin sequence. In round-robin mode, the part
continuously measures all channels.
The third temperature measurement method is initiated after
every read or write to the part when the part is in either single-
channel measurement mode or round robin measurement mode.
Once serial communication has started, any conversion in pro-
gress is stopped and the ADC reset. Conversion starts again
immediately after the serial communication has finished. The
temperature measurement proceeds normally as described earlier.
VDD MONITORING
The ADT7316/ADT7317/ADT7318 can monitor their own power
supplies. The parts measure the voltage on their VDD pin to a
resolution of 10 bits. The resulting value is stored in two 8-bit
registers: the 2 LSBs are stored in the Internal Temperature
Value/VDD Value register (Address 0x03) and the 8 MSBs are
stored in the VDD Value Register MSBs register (Address 0x06).
This allows the user to perform a 1-byte read if 10-bit resolution
is not important. The measured result is compared with VHIGH
and VLOW limits. If the VDD interrupt is not masked out, any out-
of-limit comparison generates a flag in the Interrupt Status 2
register (Address 0x10), and one or more out-of-limit results
cause the INT/INT output to pull either high or low depending
on the output polarity setting.
Measuring the voltage on the VDD pin is regarded as monitoring
a channel. Therefore, along with the internal and external tem-
perature sensors, the VDD voltage makes up the third and final
monitoring channel. The user can select the VDD channel for
single-channel measurement by setting Bit C4 = 1 and setting
Bit C0 to Bit C2 to all 0s in the Control Configuration 2 register
(Address 0x19).
When measuring the VDD value, the reference for the ADC
is sourced from the internal reference. Table 8 shows the data
format. As the maximum VDD voltage measurable is 7 V,
internal scaling is performed on the VDD voltage to match the
2.28 V internal reference value. An example of how the transfer
function works follows.
VDD = 5 V
ADC Reference = 2.28 V
1 LSB = ADC Reference/210 = 2.28/1024 = 2.226 mV
Scale Factor = Full-Scale VCC/ADC Reference = 7/2.28 = 3.07
Conversion Result = VDD/(Scale Factor × LSB Size)
= 5/(3.07 × 2.226 mV)
= 0x2DB
Rev. B | Page 23 of 44
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