a
FEATURES
4 or 8 Analog Input Channels
Built-In Track-and-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
LC2MOS High Speed
4- and 8-Channel 8-Bit ADCs
AD7824/AD7828
FUNCTIONAL BLOCK DIAGRAM
VREF (+)
AIN1
AIN4
DB7
DB6
DB5
DB4
4-BIT
FLASH
ADC
(4MSB)
VREF (–)
VREF (+)
16
AIN8
THREESTATE
DRIVERS
4-BIT
DAC
MUX*
DB3
DB2
DB1
DB0
4-BIT
FLASH
ADC
(4LSB)
ADDRESS
LATCH
DECODE
TIMING AND CONTROL
CIRCUITRY
A0 A1 A2**
RDY
CS
INT
RD
*AD7824 – 4-CHANNEL MUX
**AD7828 – 8-CHANNEL MUX
A2 – AD7828 ONLY
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The AD7824 and AD7828 are high speed, multichannel, 8-bit
ADCs with a choice of four (AD7824) or eight (AD7828) multiplexed analog inputs. A half-flash conversion technique gives a fast
conversion rate of 2.5 µs per channel, and the parts have a built-in
track-and-hold function capable of digitizing full-scale signals of
10 kHz (157 mV/µs 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.
1. 4- or 8-channel input multiplexer gives cost effective,
space-saving multichannel ADC system.
Microprocessor interfacing of the parts is simple, using standard
Chip Select (CS) and Read (RD) signals to initiate the conversion
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.
2. Fast conversion rate of 2.5 µs/channel features a per-channel
sampling frequency of 100 kHz for the AD7824 or 50 kHz
for the AD7828.
3. Built-in track-and-hold function allows handling of four or
eight channels up to 10 kHz bandwidth (157 mV/µs 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.
The AD7824 and AD7828 are fabricated in an advanced, all
ion-implanted, linear compatible CMOS process (LC2MOS) 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 surfacemount packages.
REV. F
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