AD7367-5ARUZ AD [Analog Devices], AD7367-5ARUZ Datasheet - Page 31

• Manufacturer Part Number: AD7367-5ARUZ
• Description: 1 MSPS, 8-Channel, Software-Selectable, True Bipolar Input, 12-Bit Plus Sign ADC
• Manufacturer: AD [Analog Devices]

REFERENCE
The AD7329 can operate with either the internal 2.5 V on-chip
reference or an externally applied reference. The internal
reference is selected by setting the Ref bit in the control register
to 1. On power-up, the Ref bit is 0, which selects the external
reference for the AD7329 conversion. Suitable reference sources
for the AD7329 include AD780, AD1582, ADR431, REF193,
and ADR391.
The internal reference circuitry consists of a 2.5 V band gap
reference and a reference buffer. When operating the AD7329
in internal reference mode, the 2.5 V internal reference is
available at the REF
to AGND using a 680 nF capacitor. It is recommended that the
internal reference be buffered before applying it elsewhere in
the system. The internal reference is capable of sourcing up to
90 μA.
On power-up, if the internal reference operation is required for
the ADC conversion, a write to the control register is necessary
to set the Ref bit to 1. During the control register write, the
conversion result from the first initial conversion is invalid. The
reference buffer requires 500 μs to power up and charge the
680 nF decoupling capacitor during the power-up time.
The AD7329 is specified for a 2.5 V to 3 V reference range.
When a 3 V reference is selected, the ranges are ±12 V, ±6 V,
±3 V, and 0 V to +12 V. For these ranges, the V
must be equal to or greater than the maximum analog input
range selected.
V
The AD7329 has a V
the serial interface operates. V
interface to both 3 V and 5 V processors. For example, if the
AD7329 is operated with a V
powered from a 3 V supply. This allows the AD7329 to accept
large bipolar input signals with low voltage digital processing.
DRIVE
IN
DRIVE
/REF
feature to control the voltage at which
OUT
CC
pin, which should be decoupled
DRIVE
of 5 V, the V
allows the ADC to easily
DRIVE
DD
pin can be
and V
SS
supply
Rev. 0 | Page 31 of 40
TEMPERATURE INDICATOR
The AD7329 has an on-chip temperature indicator. The
temperature indicator can be used to provide local temperature
measurements on the AD7329. To access the temperature
indicator, the ADC should be configured in pseudo differential
mode, Mode 1 = Mode 0 = 1, which sets Channel Bits ADD2,
ADD1, and ADD0 to 1. V
small dc voltage within the specified pseudo input range for the
selected analog input range. When a conversion is initiated in
this configuration, the output code represents the temperature
(see Figure 50). When using the temperature indicator on the
AD7329, the part should be operated at low throughput rates, such
as approximately 30 kSPS for the ±2.5 V range. The throughput
rate is reduced for the temperature indicator mode because the
AD7329 requires more acquisition time for this mode.
5450
5400
5350
5300
5250
5200
5150
5100
5050
Figure 50. Temperature vs. ADC Output Code for ±2.5 V Range
4420
4410
4400
4390
4380
4370
4360
4350
4340
Figure 51. Temperature vs. ADC Output Code for ±10 V Range
–40
–40
–20
–20
0
0
IN
TEMPERATURE (°C)
TEMPERATURE (°C)
±10V RANGE, INT REF
7 must be tied to AGND or to a
20
20
40
V
V
±2.5V RANGE
INTERNAL REFERENCE
30kSPS
CC
DD
40
= V
= 12V, V
V
V
50kSPS
CC
DD
60
DRIVE
/V
= V
SS
DRIVE
SS
60
= ±12V
= 5V
80
= –12V
AD7329
= 5V
100
80