AD7908 Datasheet, PDF (1/24 Pages) Analog Devices – 8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP

8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs
with Sequencer in 20-Lead TSSOP
AD7908/AD7918/AD7928
FEATURES
Fast Throughput Rate: 1 MSPS
Specified for AV_DD of 2.7 V to 5.25 V
Low Power:
6.0 mW Max at 1 MSPS with 3 V Supply
13.5 mW Max at 1 MSPS with 5 V Supply
8 (Single-Ended) Inputs with Sequencer
Wide Input Bandwidth:
AD7928, 70 dB Min SINAD at 50 kHz Input Frequency
Flexible Power/Serial Clock Speed Management
No Pipeline Delays
High Speed Serial Interface SPI^®/QSPI™/
MICROWIRE™/DSP Compatible
Shutdown Mode: 0.5 ␮A Max
20-Lead TSSOP Package
GENERAL DESCRIPTION
The AD7908/AD7918/AD7928 are, respectively, 8-bit, 10-bit,
and 12-bit, high speed, low power, 8-channel, successive
approximation ADCs. The parts operate from a single 2.7 V
to 5.25 V power supply and feature throughput rates up to
1 MSPS. The parts contain a low noise, wide bandwidth track-
and-hold amplifier that can handle input frequencies in excess
of 8 MHz.
The conversion process and data acquisition are controlled using
CS and the serial clock signal, allowing the device to easily inter-
face with microprocessors or DSPs. The input signal is sampled
on the falling edge of CS and conversion is also initiated at this
point. There are no pipeline delays associated with the part.
The AD7908/AD7918/AD7928 use advanced design techniques to
achieve very low power dissipation at maximum throughput rates.
At maximum throughput rates, the AD7908/AD7918/AD7928
consume 2 mA maximum with 3 V supplies; with 5 V supplies, the
current consumption is 2.7 mA maximum.
Through the configuration of the Control Register, the analog
input range for the part can be selected as 0 V to REF_IN or 0 V to
2 Ï« REF_IN, with either straight binary or twos complement out-
put coding. The AD7908/AD7918/AD7928 each feature eight
single-ended analog inputs with a channel sequencer to allow a
preprogrammed selection of channels to be converted sequentially.
The conversion time for the AD7908/AD7918/AD7928 is deter-
mined by the SCLK frequency, which is also used as the master
clock to control the conversion.
REV. A
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REF_IN
V_IN0
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V_IN7
FUNCTIONAL BLOCK DIAGRAM
AV_DD
T/H
I/P
MUX
8-/10-/12-BIT
SUCCESSIVE
APPROXIMATION
ADC
SEQUENCER
CONTROL LOGIC
AD7908/AD7918/AD7928
GND
SCLK
DOUT
DIN
CS
V_DRIVE
PRODUCT HIGHLIGHTS
1. High Throughput with Low Power Consumption.
The AD7908/AD7918/AD7928 offer up to 1 MSPS throughput
rates. At the maximum throughput rate with 3 V supplies, the
AD7908/AD7918/AD7928 dissipate just 6 mW of power
maximum.
2. Eight Single-Ended Inputs with a Channel Sequencer.
A sequence of channels can be selected, through which the
ADC will cycle and convert on.
3. Single-Supply Operation with V_DRIVE Function.
The AD7908/AD7918/AD7928 operate from a single 2.7 V to
5.25 V supply. The V_DRIVE function allows the serial interface
to connect directly to either 3 V or 5 V processor systems
independent of AV_DD.
4. Flexible Power/Serial Clock Speed Management.
The conversion rate is determined by the serial clock, allowing
the conversion time to be reduced through the serial clock
speed increase. The parts also feature various shutdown
modes to maximize power efficiency at lower throughput rates.
Current consumption is 0.5 µA max when in full shutdown.
5. No Pipeline Delay.
The parts feature a standard successive approximation ADC
with accurate control of the sampling instant via a CS input
and once off conversion control.
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