AD7938-6 Datasheet, PDF (1/32 Pages) Analog Devices – 8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer

FEATURES
Fast throughput rate: 625 kSPS
Specified for VDD of 2.7 V to 5.25 V
Low power
3.6 mW max at 625 kSPS with 3 V supplies
7.5 mW max at 625 kSPS with 5 V supplies
8 analog input channels with a sequencer
Software configurable analog inputs
8-channel single-ended inputs
4-channel fully differential inputs
4-channel pseudo-differential inputs
7-channel pseudo-differential inputs
Accurate on-chip 2.5 V reference
±0.2% max @ 25°C, 25 ppm/°C max
70 dB SINAD at 50 kHz input frequency
No pipeline delays
High speed parallel interface—word/byte modes
Full shutdown mode: 2 µA max
32-lead LFCSP and TQFP package
GENERAL DESCRIPTION
The AD7938-6 is a 12-bit high speed, low power, successive
approximation (SAR) ADC. The part operates from a single
2.7 V to 5.25 V power supply and features throughput rates up
to 625 kSPS. The part contains a low noise, wide bandwidth,
differential track-and-hold amplifier that can handle input
frequencies up to 50 MHz.
The AD7938-6 features eight analog input channels with a
channel sequencer that allows a preprogrammed selection of
channels to be converted sequentially. The part can operate
with either single-ended, fully differential, or pseudo-
differential analog inputs.
The conversion process and data acquisition are controlled
using standard control inputs that allow easy interfacing with
microprocessors and DSPs. The input signal is sampled on the
falling edge of CONVST and the conversion is also initiated at
this point.
The AD7938-6 has an accurate on-chip 2.5 V reference that
can be used as the reference source for the analog-to-digital
conversion. Alternatively, this pin can be overdriven to provide
an external reference.
Rev. 0
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8-Channel, 625 kSPS, 12-Bit
Parallel ADCs with a Sequencer
AD7938-6
V_REFIN/
V_REFOUT
V_IN0
V_IN7
FUNCTIONAL BLOCK DIAGRAM
V_DD
AGND
AD7938-6
2.5V
VREF
I/P
MUX
T/H
12-BIT
SAR ADC
AND
CONTROL
CLKIN
CONVST
BUSY
SEQUENCER
PARALLEL INTERFACE/CONTROL REGISTER
V_DRIVE
DB0 DB11
CS RD WR W/B
Figure 1.
DGND
The AD7938-6 uses advanced design techniques to achieve very
low power dissipation at high throughput rates. The part also
features flexible power management options. An on-chip
control register allows the user to set up different operating
conditions, including analog input range and configuration,
output coding, power management, and channel sequencing.
PRODUCT HIGHLIGHTS
1. High throughput with low power consumption.
2. Eight analog inputs with a channel sequencer.
3. Accurate on-chip 2.5 V reference.
4. Software configurable analog inputs. Single-ended, pseudo-
differential, or fully differential analog inputs that are
software selectable.
5. Single-supply operation with VDRIVE function. The VDRIVE
function allows the parallel interface to connect directly to
3 V, or 5 V processor systems independent of VDD.
6. No pipeline delay.
7. Accurate control of the sampling instant via a CONVST
input and once off conversion control.
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