8-Channel, 625 kSPS, 12-Bit
Parallel ADCs with a Sequencer
AD7938-6
Data Sheet
FEATURES
FUNCTIONAL BLOCK DIAGRAM
VDD
AGND
AD7938-6
VREFIN/
VREFOUT
2.5V
VREF
VIN0
I/P
MUX
CLKIN
12-BIT
SAR ADC
AND
CONTROL
T/H
CONVST
BUSY
VIN7
SEQUENCER
VDRIVE
PARALLEL INTERFACE/CONTROL REGISTER
DB0 DB11
CS RD WR W/B
04751-001
Throughput rate: 625 kSPS
Specified for VDD of 2.7 V to 5.25 V
Power consumption
3.6 mW maximum at 625 kSPS with 3 V supplies
7.5 mW maximum 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% maximum @ 25°C, 25 ppm/°C maximum
69 dB SINAD at 50 kHz input frequency
No pipeline delays
High speed parallel interface with word/byte modes
Full shutdown mode: 2 µA maximum
32-lead LFCSP and TQFP packages
DGND
Figure 1.
GENERAL DESCRIPTION
The AD7938-6 is a 12-bit, high speed, low power, successive
approximation (SAR) analog-to-digital converter (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 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.
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.
2.
3.
4.
5.
6.
7.
High throughput with low power consumption.
Eight analog inputs with a channel sequencer.
Accurate on-chip 2.5 V reference.
Single-ended, pseudo differential, or fully differential
analog inputs that are software selectable.
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.
No pipeline delay.
Accurate control of the sampling instant via a CONVST
input and once-off conversion control.
Table 1.
Similar Device
AD7938/AD7939
AD7933/AD7934
AD7934-6
No. of Bits
12/10
10/12
12
No. of Channels
8
4
4
Speed
1.5 MSPS
1.5 MSPS
625 kSPS
The AD7938-6 uses advanced design techniques to achieve very
low power dissipation at high throughput rates. The part also
Rev. D
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