AD7864_09 Datasheet, PDF (1/28 Pages) Analog Devices – 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC

4-Channel, Simultaneous Sampling,
High Speed, 12-Bit ADC
AD7864
FEATURES
High speed (1.65 μs) 12-bit ADC
4 simultaneously sampled inputs
4 track-and-hold amplifiers
0.35 μs track-and-hold acquisition time
1.65 μs conversion time per channel
HW/SW select of channel sequence for conversion
Single-supply operation
Selection of input ranges
±10 V, ±5 V for AD7864-1
±2.5 V for AD7864-3 0 V to 2.5 V, 0 V to 5 V for AD7864-2
High speed parallel interface that allows
Interfacing to 3 V processors
Low power, 90 mW typical
Power saving mode, 20 μW typical
Overvoltage protection on analog inputs
APPLICATIONS
AC motor control
Uninterrupted power supplies
Data acquisition systems
Communications
GENERAL DESCRIPTION
The AD7864 is a high speed, low power, 4-channel, simulta-
neous sampling 12-bit analog-to-digital converter (ADC) that
operates from a single 5 V supply. The part contains a 1.65 μs
successive approximation ADC, four track-and-hold amplifiers,
a 2.5 V reference, an on-chip clock oscillator, signal conditioning
circuitry, and a high speed parallel interface. The input signals
on four channels sample simultaneously preserving the relative
phase information of the signals on the four analog inputs. The
part accepts analog input ranges of ±10 V, ±5 V (AD7864-1), 0 V
to +2.5 V, 0 V to +5 V (AD7864-2), and ±2.5 V (AD7864-3).
Any subset of the four channels can be converted to maximize
the throughput rate on the selected sequence. Select the channels to
convert via hardware (channel select input pins) or software (pro-
gramming the channel select register).
A single conversion start signal (CONVST) simultaneously places
all the track-and-holds into hold and initiates a conversion se-
quence for the selected channels. The EOC signal indicates the end
of each individual conversion in the selected conversion sequence.
The BUSY signal indicates the end of the conversion sequence.
FUNCTIONAL BLOCK DIAGRAM
AV_DD
V_REF V_REFGND DVDD VDRIVE
STBY
V_IN1A
V_IN1B
V_IN2A
V_IN2B
V_IN3A
V_IN3B
V_IN4A
V_IN4B
TRACK-AND-HOLD
×4
SIGNAL
SCALING
SIGNAL
SCALING
SIGNAL
SCALING
MUX
SIGNAL
SCALING
FRSTDATA
BUSY
EOC
CONVERSION
CONTROL LOGIC
6kΩ
2.5V
REFERENCE
AD7864
DGND
AGND
RD
12-BIT
ADC
OUTPUT
DATA
REGISTERS
DB11
DB0
SOFTWARE
LATCH
DB0 TO DB3
CS
WR
INT/EXT CLOCK
INT
SELECT
CLOCK
CONVST ^{SL1 SL2 SL3 SL4} H/S ^CLKIN INT/EXT ^{AGND AGND}
SEL
CLK
Figure 1.
Data is read from the part by a 12-bit parallel data bus using the
standard CS and RD signals. Maximum throughput for a single
channel is 500 kSPS. For all four channels, the maximum throughput
is 130 kSPS for the read-during-conversion sequence operation.
The throughput rate for the read-after-conversion sequence
operation depends on the read cycle time of the processor. See
the Timing and Control section. The AD7864 is available in a
small (0.3 square inch area) 44-lead MQFP.
PRODUCT HIGHLIGHTS
1. Four track-and-hold amplifiers and a fast (1.65 μs) ADC for
simultaneous sampling and conversion of any subset of the
four channels.
2. A single 5 V supply consuming only 90 mW typical, makes
it ideal for low power and portable applications. See the
Standby Mode Operation section.
3. High speed parallel interface for easy connection to micro-
processors, microcontrollers, and digital signal processors.
4. Available in three versions with different analog input
ranges. The AD7864-1 offers the standard industrial input
ranges of ±10 V and ±5 V; the AD7864-3 offers the common
signal processing input range of ±2.5 V; the AD7864-2 can
be used in unipolar, 0 V to 2.5 V and 0 V to 5 V,
applications.
5. Features very tight aperture delay matching between the
four input sample-and-hold amplifiers.
Rev. D
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