a
FEATURES
Fast (2.4 s) 14-Bit ADC
Four Simultaneously Sampled Inputs
Four Track/Hold Amplifiers
0.35 s Track/Hold Acquisition Time
2.4 s Conversion Time per Channel
HW/SW Select of Channel Sequence for Conversion
Single Supply Operation
Selection of Input Ranges: ؎10 V, ؎5 V and ؎2.5 V,
0 V to 5 V and 0 V to 2.5 V
High Speed Parallel Interface Which Also Allows
Interfacing to 3 V Processors
Low Power, 115 mW Typ
Power Saving Mode, 15 W Typ
Overvoltage Protection on Analog Inputs
Four-Channel, Simultaneous
Sampling, Fast, 14-Bit ADC
AD7865
FUNCTIONAL BLOCK DIAGRAM
VREF
AVDD
STBY
VIN1A
VIN1B
VIN2A
VIN2B
VIN3A
VIN3B
VIN4A
VIN4B
VREFAGND
6k⍀
VDRIVE
+2.5V
REFERENCE
TRACK/HOLD
؋4
DGND
AD7865
SIGNAL
SCALING
SIGNAL
SCALING
DVDD
AGND
RD
MUX
SIGNAL
SCALING
14-BIT
ADC
OUTPUT
LATCH
CHANNEL
SELECT
REGISTER
SIGNAL
SCALING
DB13
DB0
DB0–DB3
CS
WR
FRSTDATA
APPLICATIONS
AC Motor Control
Uninterruptible Power Supplies
Industrial Power Meters/Monitors
Data Acquisition Systems
Communications
GENERAL DESCRIPTION
The AD7865 is a fast, low power, four-channel simultaneous
sampling 14-bit A/D converter that operates from a single 5 V
supply. The part contains a 2.4 µs successive approximation
ADC, four track/hold amplifiers, 2.5 V reference, 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, ± 2.5 V, 0 V to 2.5 V and 0 V to 5 V.
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 either via hardware (channel select input pins) or via software (programming
the channel select register).
A single conversion start signal (CONVST) simultaneously places
all the track/holds into hold and initiates 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.
Data is read from the part via a 14-bit parallel data bus using the
standard CS and RD signals. Maximum throughput for a single
channel is 350 kSPS. For all four channels the maximum throughput is 100 kSPS.
BUSY
EOC
CONVERSION
CONTROL LOGIC
CONVST
INT/EXT
CLOCK
SELECT
INT
CLOCK
SL3 SL4 H/S CLK IN INT/EXT AGND AGND
SEL /SL1 CLK/SL2
The AD7865 is available in a small (0.3 sq. inch area) 44-lead
PQFP.
PRODUCT HIGHLIGHTS
1. The AD7865 features four Track/Hold amplifiers and a fast
(2.4 µs) ADC allowing simultaneous sampling and then conversion of any subset of the four channels.
2. The AD7865 operates from a single 5 V supply and consumes only 115 mW typ, making it ideal for low power and
portable applications.
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 AD7865-1 offers the standard industrial
ranges of ± 10 V and ± 5 V; the AD7865-2 offers a unipolar
range of 0 V to 2.5 V or 0 V to 5 V and the AD7865-3 offers
the common signal processing input range of ± 2.5 V.
5. The part features very tight aperture delay matching between
the four input sample and hold amplifiers.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
