ADT7317ARQZ-REEL71 查看數據表（PDF） - Analog Devices
零件编号
产品描述 (功能)
生产厂家
ADT7317ARQZ-REEL71
Analog Devices
ADT7317ARQZ-REEL71 Datasheet PDF : 44 Pages
| |||
ADT7316/ADT7317/ADT7318
VDD
I
OPTIONAL CAPACITOR, UP TO
3nF MAX. CAN BE ADDED TO
IMPROVE HIGH FREQUENCY
NOISE REJECTION IN NOISY
ENVIRONMENTS
REMOTE
SENSING
TRANSISTOR
(2N3906)
D+
C1
D–
LOW-PASS
FILTER
fC = 65kHz
N×I
BIAS
DIODE
IBIAS
VOUT+
TO ADC
VOUT–
Figure 41. Signal Conditioning for External Diode Temperature Sensors
The buffered/unbuffered option is controlled by the DAC
Configuration register (Address 0x1B; see the Registers
section). The LDAC Configuration register controls the
selection between internal and external voltage references.
The default setting is for external reference to be selected.
VREF-AB
2.25V INTERNAL
VREF
STRING
DAC A
STRING
DAC B
Figure 42. DAC Reference Buffer Circuit
OUTPUT AMPLIFIER
The output buffer amplifier is capable of generating output
voltages to within 1 mV of either rail. Its actual range depends
on the value of VREF, gain, and offset error.
If a gain of 1 is selected (Bit 0 to Bit 3 = 0, DAC Configuration
register, Address 0x1B), the output range is 0.001 V to VREF.
If a gain of 2 is selected (Bit 0 to Bit 3 = 1, DAC Configuration
register, Address 0x1B), the output range is 0.001 V to 2 VREF.
Because of clamping, however, the maximum output is limited
to VDD – 0.001 V.
The output amplifier is capable of driving a load of 4.7 kΩ to
VDD or 4.7 kΩ to GND in parallel with 200 pF to GND (see
Figure 6). The source and sink capabilities of the output
amplifier can be seen in Figure 20.
The slew rate is 0.7 V/μs with a half-scale settling time to
±0.5 LSB (at 8 bits) of 6 μs.
THERMAL VOLTAGE OUTPUT
proportional to output voltage. Each time a temperature
measurement is taken, the DAC output is updated. The out-
put resolution for the ADT7318 is 8 bits with the 1°C change
corresponding to the 1 LSB change. The output resolution for
the ADT7316 and ADT7317 is capable of 10 bits with a 0.25°C
change corresponding to the 1 LSB change.
The default output resolution for the ADT7316 and ADT7317
is 8 bits. To increase this to 10 bits, set C1 = 1 of the Control
Configuration 3 register (Address 0x1A). The default output
range is 0 V to VREF-AB, and this can be increased to 0 V to
2 VREF-AB. The user can select the internal VREF (VREF = 2.28 V)
by setting D4 = 1 in the LDAC Configuration register (Address
0x1C). Increasing the output voltage span to 2 VREF can be done
by setting D0 = 1 for DAC A (internal temperature sensor), and
D1 = 1 for DAC B (external temperature sensor) in the DAC
Configuration register (Address 0x1B).
The output voltage is capable of tracking a maximum tem-
perature range of −128°C to +127°C, but the default setting is
−40°C to +127°C. If the output voltage range is 0 V to VREF-AB
(VREF-AB = 2.25 V), then this corresponds to 0 V representing
−40°C, and 1.48 V representing +127°C. This gives an upper
dead band between 1.48 V and VREF-AB.
The internal and external analog temperature offset registers
can be used to vary this upper dead band, and consequently,
the temperature that 0 V corresponds to. Table 6 and Table 7
give examples of how this is done using a DAC output voltage
span of VREF and 2 VREF, respectively. Write in the temperature
value, in twos complement format, at which 0 V is to start. For
example, if using the DAC A output with 0 V to start at −40°C,
program 0xD8 into the internal analog temperature offset regis-
ter (Address 0x21). This is an 8-bit register, and thus, only has a
temperature offset resolution of 1°C for all device models. Use
the following formulas to determine the value to program into
the offset registers.
The ADT7316/ADT7317/ADT7318 are capable of outputting
voltages that are proportional to temperature. The DAC A
output can be configured to represent the temperature of the
internal sensor while DAC B output can be configured to
represent the external temperature sensor. Bit C5 and Bit C6
of the Control Configuration 3 register select the temperature
Rev. B | Page 21 of 44
Share Link: 