AD7829-1 Datasheet, PDF (1/20 Pages) Analog Devices – 3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC

3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC
AD7829-1
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, VDD = 3 V ± 10%
0 V to 2.5 V p-p, VDD = 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 EOC A0 A1 A2
V_DD
CONTROL
LOGIC
COMP
2.5V
REF
V_IN1
V_IN2
V_IN3
V_IN4
V_IN5
V_IN6
V_IN7
V_IN8
INPUT
MUX
T/H
8-BIT
HALF
FLASH
ADC
BUF
PARALLEL
PORT
V_{MID AGND DGND}
Figure 1.
CS RD
V_{REF IN/OUT}
DB7
DB0
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 VMID 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.
Rev. 0
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