Data Sheet
8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs
with Sequencer in 20-Lead TSSOP
AD7908/AD7918/AD7928
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Fast throughput rate: 1 MSPS
Specified for AVDD 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
Eight (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 μA max
20-lead TSSOP package
Qualified for automotive applications
AVDD
REFIN
VIN0
•
•
•
•
•
•
•
•
•
•
•
•
•
T/H
8-/10-/12-BIT
SUCCESSIVE
APPROXIMATION
ADC
I/P
MUX
VIN7
SCLK
DOUT
CONTROL LOGIC
SEQUENCER
DIN
CS
GENERAL DESCRIPTION
VDRIVE
GND
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 interface
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 REFIN or 0 V to 2 ×
REFIN, with either straight binary or twos complement output
coding. The AD7908/AD7918/AD7928 each feature eight singleended 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
determined by the SCLK frequency, which is also used as the
master clock to control the conversion.
Rev. E
03089-001
AD7908/AD7918/AD7928
Figure 1.
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 cycles and converts on.
3. Single-Supply Operation with VDRIVE Function. The AD7908/
AD7918/AD7928 operate from a single 2.7 V to 5.25 V supply.
The VDRIVE function allows the serial interface to connect directly
to either 3 V or 5 V processor systems independent of AVDD.
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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