AD7938 Ver la hoja de datos (PDF) - Analog Devices
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AD7938 Datasheet PDF : 32 Pages
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8-Channel, 1.5 MSPS, 12-Bit and 10-Bit
Parallel ADCs with a Sequencer
AD7938/AD7939
FEATURES
Fast throughput rate: 1.5 MSPS
Specified for VDD of 2.7 V to 5.25 V
Low power
6 mW max at 1.5 MSPS with 3 V supplies
13.5 mW max at 1.5 MSPS 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/AD7939 are 12-bit and 10-bit, high speed, low
power, successive approximation (SAR) ADCs. The parts
operate from a single 2.7 V to 5.25 V power supply and feature
throughput rates up to 1.5 MSPS. The parts contain a low noise,
wide bandwidth, differential track-and-hold amplifier that can
handle input frequencies up to 50 MHz.
The AD7938/AD7939 feature eight analog input channels with
a channel sequencer that allow a preprogrammed selection of
channels to be converted sequentially. These parts 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/AD7939 have 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
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
VREFIN/
VREFOUT
VIN0
VIN7
FUNCTIONAL BLOCK DIAGRAM
VDD
AGND
AD7938/AD7939
2.5V
VREF
I/P
MUX
T/H
12-/10-BIT
SAR ADC
AND
CONTROL
CLKIN
CONVST
BUSY
SEQUENCER
PARALLEL INTERFACE/CONTROL REGISTER
VDRIVE
DB0 DB11
CS RD WR W/B
Figure 1.
DGND
These parts use advanced design techniques to achieve very
low power dissipation at high throughput rates. They also
feature 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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
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