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AD7655
*
Low Cost 4-Channel 1 MSPS 16-Bit ADC
FUNCTIONAL BLOCK DIAGRAM
CLOCK AND
CONTROL LOGIC
A/B
16
D[15:0]
BUSY
CS
SER/PAR
OGND
OVDD
DGNDDVDD
SERIAL
PORT
PARALLEL
INTERFACE
BYTESWAP
RD
AVDD AGND REFxREFGND
PD
RESET
CNVST
INAN
SWITCHED
CAP DAC
AD7655
INA1
TRACK/HOLD
H115472
IMPULSE
MUX
MUX
EOC
MUX
INA2
A0
INB1
INBN
INB2
PulSAR Selection
Type/kSPS 100–250 500–570 800–1000
Pseudo AD7651 AD7650/AD7652 AD7653
Differential AD7660/AD7661 AD7664/AD7666 AD7667
True Bipolar AD7663 AD7665 AD7671
True Differential AD7675 AD7676 AD7677
18-Bit AD7678 AD7679 AD7674
Multichannel/ AD7654
Simultaneous AD7655
PRODUCT HIGHLIGHTS
1. Multichannel ADC
The AD7655 features 4-channel inputs with two sample-
and-hold circuits that allow simultaneous sampling.
2. Fast Throughput
The AD7655 is a very high speed (1 MSPS in normal mode
and 888 kSPS in impulse mode), charge redistribution, 16-bit
SAR ADC that avoids pipeline delay.
3. Single-Supply Operation
The AD7655 operates from a single 5 V supply and dissipates
only 120 mW typical, even lower when a reduced throughput
is used with the reduced power mode (Impulse) and a power-
down mode.
4. Serial or Parallel Interface
Versatile parallel or 2-wire serial interface arrangement
compatible with both 3 V or 5 V logic.
*Patent pending
FEATURES
4-Channel, 16-Bit Resolution ADC
2 Track-and-Hold Amplifiers Throughput:
1 MSPS (Normal Mode)
888 kSPS (Impulse Mode)
Analog Input Voltage Range: 0 V to 5 V
No Pipeline Delay
Parallel and Serial 5 V/3 V Interface
SPI
®
/QSPI™/MICROWIRE™/DSP Compatible
Single 5 V Supply Operation
Power Dissipation
120 mW Typical,
2.6 mW @ 10 kSPS
Package: 48-Lead Quad Flat Pack (LQFP) or
48-Lead Frame Chip Scale Pack (LFCSP)
Pin-to-Pin Compatible with the AD7654
Low Cost
APPLICATIONS
4-Channel Data Acquisition
GENERAL DESCRIPTION
The AD7655 is a low cost, 4-channel, 16-bit, charge redistribution
SAR, analog-to-digital converter that operates from a single 5 V
power supply. It contains two low noise, wide bandwidth track-and-
hold amplifiers that allow simultaneous sampling, a high speed
1MSPS 16-bit sampling ADC, an internal conversion clock,
error correction circuits, and both serial and parallel system
interface ports. Each track-and-hold has a multiplexer in front
to provide a 4-channel input ADC.
The AD7655 features a very high sampling rate mode (Normal)
and, for low power applications, a reduced power mode (Impulse)
where the power is scaled with the throughput. It is available
in 48-lead LQFP or 48-lead LFCSP packages with operation
specified from –40∞C to +85∞C.