FUNCTIONAL BLOCK DIAGRAM
2.5V
REFERENCE
CALIBRATION MEMORY
AND
CONTROLLER
PARALLEL INTERFACE/CONTROL REGISTER
I/P
MUX
CHARGE
REDISTRIBUTION
DAC
SAR + ADC
CONTROL
T/H
BUF
AIN1
AIN8
REF
IN
/
REF
OUT
C
REF1
C
REF2
CAL
DV
DD
DGND
CLKIN
CONVST
BUSY
SLEEP
AV
DD
AGND
DB15 – DB0
RD
CS
WR
W/B
AD7859/AD7859L
COMP
REV. A
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.
a
3 V to 5 V Single Supply, 200 kSPS
8-Channel, 12-Bit Sampling ADCs
AD7859/AD7859L
FEATURES
Specified for V
DD
of 3 V to 5.5 V
AD7859–200 kSPS; AD7859L–100 kSPS
System and Self-Calibration
Low Power
Normal Operation
AD7859: 15 mW (V
DD
= 3 V)
AD7859L: 5.5 mW (V
DD
= 3 V)
Using Automatic Power-Down After Conversion (25 mW)
AD7859: 1.3 mW (V
DD
= 3 V 10 kSPS)
AD7859L: 650 mW (V
DD
= 3 V 10 kSPS)
Flexible Parallel Interface:
16-Bit Parallel/8-Bit Parallel
44-Pin PQFP and PLCC Packages
APPLICATIONS
Battery-Powered Systems (Personal Digital Assistants,
Medical Instruments, Mobile Communications)
Pen Computers
Instrumentation and Control Systems
High Speed Modems
© Analog Devices, Inc., 1996
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
GENERAL DESCRIPTION
The AD7859/AD7859L are high speed, low power, 8-channel,
12-bit ADCs which operate from a single 3 V or 5 V power
supply, the AD7859 being optimized for speed and the
AD7859L for low power. The ADC contains self-calibration
and system calibration options to ensure accurate operation over
time and temperature and have a number of power-down
options for low power applications.
The AD7859 is capable of 200 kHz throughput rate while the
AD7859L is capable of 100 kHz throughput rate. The input
track-and-hold acquires a signal in 500 ns and features a pseudo-
differential sampling scheme. The AD7859 and AD7859L input
voltage range is 0 to V
REF
(unipolar) and –V
REF
/2 to +V
REF
/2
about V
REF
/2 (bipolar) with both straight binary and 2s comple-
ment output coding respectively. Input signal range is to the
supply and the part is capable of converting full-power signals to
100 kHz.
CMOS construction ensures low power dissipation of typically
5.4 mW for normal operation and 3.6 µW in power-down mode.
The part is available in 44-pin, plastic quad flatpack package
(PQFP) and plastic lead chip carrier (PLCC).
See page 28 for data sheet index.
PRODUCT HIGHLIGHTS
1. Operation with either 3 V or 5 V power supplies.
2. Flexible power management options including automatic
power-down after conversion.
3. By using the power management options a superior power
performance at slower throughput rates can be achieved.
AD7859: 1 mW typ @ 10 kSPS
AD7859L: 1 mW typ @ 20 kSPS
4. Operates with reference voltages from 1.2 V to the supply.
5. Analog input ranges from 0 V to V
DD
.
6. Self and system calibration.
7. Versatile parallel I/O port.
8. Lower power version AD7859L.
