REV. D
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
LC2MOS High Speed
4- & 8-Channel 8-Bit ADCs
AD7824/AD7828
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
FUNCTIONAL BLOCK DIAGRAM
RDY
CS
RD
INT
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
THREE
STATE
DRIVERS
4-BIT
FLASH
ADC
(4LSB)
VREF (+)
16
TIMING AND CONTROL
CIRCUITRY
ADDRESS
LATCH
DECODE
AIN 1
AIN 4
AIN 8
MUX*
*AD7824 – 4-CHANNEL MUX
**AD7828 – 8-CHANNEL MUX
A2 – AD7828 ONLY
A0 A1 A2**
VREF (+)
VREF (–)
4-BIT
FLASH
ADC
(4MSB)
4-BIT
DAC
FEATURES
4- or 8-Analog Input Channels
Built-In Track/Hold Function
10 kHz Signal Handling on Each Channel
Fast Microprocessor Interface
Single 5 V Supply
Low Power: 50 mW
Fast Conversion Rate, 2.5
s/Channel
Tight Error Specification: 1/2 LSB
GENERAL DESCRIPTION
The AD7824 and AD7828 are high-speed, multichannel, 8-bit
ADCs with a choice of 4 (AD7824) or 8 (AD7828) multiplexed
analog inputs. A half-flash conversion technique gives a fast
conversion rate of 2.5
s per channel and the parts have a built-
in track/hold function capable of digitizing full-scale signals of
10 kHz (157 mV/
s slew rate) on all channels. The AD7824 and
AD7828 operate from a single 5 V supply and have an analog
input range of 0 V to 5 V, using an external 5 V reference.
Microprocessor interfacing of the parts is simple, using standard
Chip Select (
CS) and Read (RD) signals to initiate the conver-
sion and read the data from the three-state data outputs. The
half-flash conversion technique means that there is no need to
generate a clock signal for the ADC. The AD7824 and AD7828
can be interfaced easily to most popular microprocessors.
The AD7824 and AD7828 are fabricated in an advanced, all
ion-implanted, linear-compatible CMOS process (LC
2MOS)
and have low power dissipation of 40 mW (typ). The AD7824
is available in a 0.3" wide, 24-lead “skinny” DIP, while the
AD7828 is available in a 0.6" wide, 28-lead DIP and in 28-
terminal surface mount packages.
PRODUCT HIGHLIGHTS
1. 4- or 8-channel input multiplexer gives cost-effective space-
saving multichannel ADC system.
2. Fast conversion rate of 2.5
s/channel features a per channel
sampling frequency of 100 kHz for the AD7824 or 50 kHz
for the AD7828.
3. Built-in track-hold function allows handling of 4- or 8-
channels up to 10 kHz bandwidth (157 mV/
s slew rate).
4. Tight total unadjusted error spec and channel-to-channel
matching eliminate the need for user trims.
5. Single 5 V supply simplifies system power requirements.
6. Fast, easy-to-use digital interface allows connection to most
popular microprocessors with minimal external components.
No clock signal is required for the ADC.