AD7864 Datasheet, PDF (1/19 Pages) Analog Devices – 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC

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4-Channel, Simultaneous
Sampling, High Speed, 12-Bit ADC
AD7864
FEATURES
High Speed (1.65␣ ␮s) 12-Bit ADC
Four Simultaneously Sampled Inputs
Four Track/Hold Amplifiers
0.35␣ ␮s Track/Hold Acquisition Time
1.65 ␮s 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 Which Also Allows
Interfacing to 3 V Processors
Low Power, 90 mW Typ
Power Saving Mode, 20␣ ␮W Typ
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 A/D converter that operates from a single
+5␣ V supply. The part contains a 1.65 µs successive approxima-
tion ADC, four track/hold amplifiers, 2.5 V reference, on-chip
clock oscillator, signal conditioning circuitry and a high speed
parallel interface. The input signals on four channels are
sampled simultaneously, thus preserving the relative phase infor-
mation 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 for AD7864-2 and ± 2.5␣ V (AD7864-3).
The part allows any subset of the four channels to be converted
in order to maximize the throughput rate on the selected se-
quence. The channels to be converted can be selected via either
hardware (channel select input pins) or software (programming
the channel select register).
A single conversion start signal (CONVST) simultaneously
places all the track/holds into hold and initiates 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.
Data is read from the part by means of a 12-bit parallel data
bus using the standard CS and RD signals. Maximum through-
put for a single channel is 500 kSPS. For all four channels the
FUNCTIONAL BLOCK DIAGRAM
AV_DD
V_REF V_{REF GND}
DV_DD V_DRIVE
STBY
V_IN1A
V_IN1B
V_IN2A
V_IN2B
V_IN3A
V_IN3B
V_IN4A
V_IN4B
TRACK/HOLD
؋4
SIGNAL
SCALING
SIGNAL
SCALING
SIGNAL
SCALING
MUX
SIGNAL
SCALING
FRSTDATA
BUSY
EOC
CONVERSION
CONTROL LOGIC
6k⍀
؉2.5V
REFERENCE
AD7864
DGND
AGND
RD
12-BIT
ADC
OUTPUT
DATA
REGISTERS
DB11
DB0
SOFTWARE
LATCH
DB0–DB3
CS
INT/EXT CLOCK
SELECT
WR
INT
CLOCK
CONVST SL1 SL2 SL3 SL4 H/S CLKIN INT/EXT AGND AGND
SEL
CLK
maximum throughput is 130 kSPS for the read during conver-
sion sequence operation. The throughput rate for the read after
conversion sequence operation will depend on the read cycle
time of the processor. See Timing and Control section.
The AD7864 is available in a small (0.3 sq. inch area) 44-lead
MQFP.
PRODUCT HIGHLIGHTS
1. The AD7864 features four Track/Hold amplifiers and a fast
(1.65 µs) ADC allowing simultaneous sampling and then
conversion of any subset of the four channels.
2. The AD7864 operates from a single +5␣ V supply and consumes
only 90 mW typ making it ideal for low power and portable
applications. Also see Standby Mode Operation.
3. The part offers a high speed parallel interface for easy con-
nection to microprocessors, microcontrollers and digital
signal processors.
4. The part is offered 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, 0 V to 5 V
applications.
5. The part features very tight aperture delay matching between
the four input sample-and-hold amplifiers.
REV. A
Information furnished by Analog Devices is believed to be accurate and
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use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 1999