AD7997 Datasheet, PDF (1/32 Pages) Analog Devices – 8-Channel, 10- and 12-Bit ADCs with I2CCompatible

8-Channel, 10- and 12-Bit ADCs with I²C-
Compatible Interface in 20-Lead TSSOP
AD7997/AD7998
FEATURES
10- and 12-bit ADC with fast conversion time: 2 µs typ
8 single-ended analog input channels
Specified for VDD of 2.7 V to 5.5 V
Low power consumption
Fast throughput rate: up to 188 kSPS
Sequencer operation
Automatic cycle mode
I²C®-compatible serial interface supports standard, fast,
and high speed modes
Out-of-range indicator/alert function
Pin-selectable addressing via AS
Shutdown mode: 1 µA max
Temperature range: −40°C to +85°C
20-lead TSSOP package
See the AD7992 and AD7994 for 2-channel and 4-channel
equivalent devices, respectively
GENERAL DESCRIPTION
The AD7997/AD7998 are 8-channel, 10- and 12-bit, low power,
successive approximation ADCs with an I²C-compatible
interface. The parts operate from a single 2.7 V to 5.5 V power
supply and feature a 2 µs conversion time. The parts contain an
8-channel multiplexer and track-and-hold amplifier that can
handle input frequencies up to 11 MHz.
The AD7997/AD7998 provide a 2-wire serial interface that is
compatible with I²C interfaces. Each part comes in two versions,
AD7997-0/AD7998-0 and AD7997-1/AD7998-1, and each
version allows at least two different I²C addresses. The I²C
interface on the AD7997-0/AD7998-0 supports standard and
fast I²C interface modes. The I²C interface on the AD7997-1/
AD7998-1 supports standard, fast, and high speed I²C interface
modes.
The AD7997/AD7998 normally remain in a shutdown state
while not converting, and power up only for conversions. The
conversion process can be controlled using the CONVST pin,
by a command mode where conversions occur across I²C write
operations or an automatic conversion interval mode selected
through software control.
The AD7997/AD7998 require an external reference that should
be applied to the REFIN pin and can be in the range of 1.2 V to
VDD. This allows the widest dynamic input range to the ADC.
FUNCTIONAL BLOCK DIAGRAM
V_DD
AGND REF_IN
CONVST
V_IN1
V_IN8
AD7997/AD7998
8:1
T/H
I/P
MUX
10-/12-BIT
SUCCESSIVE
APPROXIMATION
ADC
CONTROL
LOGIC
OSCILLATOR
DATA_LOWLIMIT
REGISTER CH1–CH4
DATA_HIGHLIMIT
REGISTER CH1–CH4
HYSTERESIS
REGISTER CH1–CH4
AS
CONVERSION
RESULT
REGISTER
CONFIGURATION
REGISTER
ALERT STATUS
REGISTER
CYCLE TIMER
REGISTER
I²C INTERFACE
ALERT/BUSY
SCL
SDA
AGND
Figure 1.
On-chip limit registers can be programmed with high and
low limits for the conversion result, and an open-drain, out-of-
range indicator output (ALERT) becomes active when the
programmed high or low limits are violated by the conversion
result. This output can be used as an interrupt.
PRODUCT HIGHLIGHTS
1. 2 µs conversion time with low power consumption.
2. I²C-compatible serial interface with pin-selectable
addresses. Two AD7997/AD7998 versions allow five
AD7997/AD7998 devices to be connected to the same
serial bus.
3. The parts feature automatic shutdown while not converting
to maximize power efficiency. Current consumption is 1 µA
max when in shutdown mode at 3V.
4. Reference can be driven up to the power supply.
5. Out-of-range indicator that can be software disabled or
enabled.
6. One-shot and automatic conversion rates.
7. Registers store minimum and maximum conversion
results.
Rev. 0
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