3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC
AD7829-1
Rev. 0
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FEATURES
8-bit half-flash ADC with 420 ns conversion time
Eight single-ended analog input channels
Available with input offset adjust
On-chip track-and-hold
SNR performance given for input frequencies
up to10 MHz
On-chip reference (2.5 V)
Automatic power-down at the end of conversion
Wide operating supply range
3 V ± 10% and 5 V ± 10%
Input ranges
0 V to 2 V p-p, V
DD
= 3 V ± 10%
0 V to 2.5 V p-p, V
DD
= 5 V ± 10%
Flexible parallel interface with
EOC
pulse to allow
stand-alone operation
APPLICATIONS
Data acquisition systems, DSP front ends
Disk drives
Mobile communication systems, subsampling
applications
GENERAL DESCRIPTION
The AD7829-1 is a high speed 8-channel, microprocessor-
compatible, 8-bit analog-to-digital converter with a maximum
throughput of 2 MSPS. The AD7829-1 contains an on-chip
reference of 2.5 V (2% tolerance); a track-and-hold amplifier;
a 420 ns, 8-bit half-flash ADC; and a high speed parallel
interface. The converter can operate from a single 3 V ± 10%
and 5 V ± 10% supply.
The AD7829-1 combines the convert start and power-down
functions at one pin, that is, the
CONVST
pin. This allows a
unique automatic power-down at the end of a conversion to be
implemented. The logic level on the
CONVST
pin is sampled
after the end of a conversion when an
EOC
(end of conversion)
signal goes high, and if it is logic low at that point, the ADC is
powered down. The parallel interface is designed to allow easy
interfacing to microprocessors and DSPs. Using only address
decoding logic, the parts are easily mapped into the microprocessor
address space.
The
EOC
pulse allows the ADCs to be used in a stand-alone
manner (see the Parallel Interface section).
FUNCTIONAL BLOCK DIAGRAM
CONVST
PARALLEL
PORT
V
REF IN/OUT
EOC
RD
CS
AGND
V
MID
A0 A1 A2
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
COMP
2.5V
REF
DD
CONTROL
LOGIC
DGND
INPUT
MUX
T/H
BUF
DB0
DB7
8-BIT
HALF
FLASH
ADC
06179-001
Figure 1.
The AD7829-1 is available in a 28-lead, wide body, small outline
IC (SOIC_W) and a 28-lead thin shrink small outline package
(TSSOP).
PRODUCT HIGHLIGHTS
1. Fast Conversion Time. The AD7829-1 has a conversion
time of 420 ns. Faster conversion times maximize the DSP
processing time in a real-time system.
2. Analog Input Span Adjustment. The V
MID
pin allows the
user to offset the input span. This feature can reduce the
requirements of single-supply op amps and take into
account any system offsets.
3. FPBW (Full Power Bandwidth) of Track-and-Hold. The
track-and-hold amplifier has excellent high frequency
performance. The AD7829-1 is capable of converting full-
scale input signals up to a frequency of 10 MHz, making
the parts ideally suited to subsampling applications.
4. Channel Selection. Channel selection is made without the
necessity of writing to the part.
