4-Channel, Simultaneous
Sampling, High Speed, 12-Bit ADC
AD7864
FEATURES
High Speed (1.65 s) 12-Bit ADC
4 Simultaneously Sampled Inputs
4 Track/Hold Amplifiers
0.35 s Track/Hold Acquisition Time
1.65 s Conversion Time per Channel
HW/SW Select of Channel Sequence for Conversion
Single-Supply Operation
Selection of Input Ranges:
؎10 V, ؎5 V for AD7864-1
؎2.5 V for AD7864-3
0 V to 2.5 V, 0 V to 5 V for AD7864-2
High Speed Parallel Interface that Allows
Interfacing to 3 V Processors
Low Power, 90 mW Typ
Power Saving Mode, 20 W Typ
Overvoltage Protection on Analog Inputs
APPLICATIONS
AC Motor Control
Uninterrupted Power Supplies
Data Acquisition Systems
Communications
GENERAL DESCRIPTION
The AD7864 is a high speed, low power, 4-channel simultaneous sampling 12-bit A/D converter that operates from a single
5 V supply. The part contains a 1.65 ms successive approximation ADC, four track/hold amplifiers, a 2.5 V reference, an
on-chip clock oscillator, signal conditioning circuitry, and a high
speed parallel interface. The input signals on four channels
are sampled simultaneously, thus preserving the relative phase
information of the signals on the four analog inputs. The part
accepts analog input ranges of ± 10 V, ± 5 V (AD7864-1), 0 V to
+2.5 V, 0 V to +5 V (AD7864-2), and ± 2.5 V (AD7864-3).
The part allows any subset of the four channels to be converted
in order to maximize the throughput rate on the selected sequence.
The channels to be converted can be selected via hardware
(channel select input pins) or software (programming the channel
select register).
A single conversion start signal (CONVST) simultaneously
places all the track/holds into hold and initiates a conversion
sequence for the selected channels. The EOC signal indicates the
end of each individual conversion in the selected conversion
sequence. The BUSY signal indicates the end of the conversion sequence.
REV. B
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. 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.
FUNCTIONAL BLOCK DIAGRAM
AVDD
STBY
VREF
TRACK/HOLD
؋4
VIN1A
VIN1B
VIN2A
VIN2B
6k⍀
SIGNAL
SCALING
VDRIVE
DVDD
VREF GND
2.5V
REFERENCE
DGND
SIGNAL
SCALING
AGND
AD7864
RD
MUX
VIN3A
VIN3B
SIGNAL
SCALING
VIN4A
VIN4B
SIGNAL
SCALING
OUTPUT
DATA
REGISTERS
SOFTWARE
LATCH
FRSTDATA
BUSY
EOC
12-BIT
ADC
CONVERSION
CONTROL LOGIC
CONVST SL1 SL2 SL3 SL4 H/S
SEL
DB0 TO DB3
DB11
DB0
CS
WR
INT/EXT CLOCK
SELECT
INT
CLOCK
CLKIN INT/EXT AGND AGND
CLK
Data is read from the part by means of a 12-bit parallel data
bus using the standard CS and RD signals. Maximum throughput for a single channel is 500 kSPS. For all four channels, the
maximum throughput is 130 kSPS for the read during conversion sequence operation. The throughput rate for the read after
conversion sequence operation depends on the read cycle time
of the processor. See the Timing and Control section.
The AD7864 is available in a small (0.3 sq. inch area) 44-lead
MQFP.
PRODUCT HIGHLIGHTS
1. The AD7864 features four track/hold amplifiers and a fast
(1.65 ms) ADC allowing simultaneous sampling and then
conversion of any subset of the four channels.
2. The AD7864 operates from a single 5 V supply and consumes
only 90 mW typ, making it ideal for low power and portable
applications. Also see the Standby Mode Operation section.
3. The part offers a high speed parallel interface for easy connection to microprocessors, microcontrollers, and digital
signal processors.
4. The part is offered in three versions with different analog
input ranges. The AD7864-1 offers the standard industrial
input ranges of ± 10 V and ± 5 V; the AD7864-3 offers the
common signal processing input range of ± 2.5 V; the
AD7864-2 can be used in unipolar 0 V to 2.5 V, 0 V to 5 V
applications.
5. The part features very tight aperture delay matching between
the four input sample-and-hold amplifiers.
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.