AD7769_15 Datasheet, PDF (1/16 Pages) Analog Devices – Analog I/O Port

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FEATURES
Two-Channel, 8-Bit 2.5 ␮s ADC
Two 8-Bit, 2.5 ␮s DACs with Output Amplifiers
Span and Offset of ADC and DAC
Independently Adjustable
Low Power
APPLICATIONS
Winchester Disk Servo Controllers
Floppy Disk Microstepping
Closed Loop Servo Systems
LC²MOS
Analog I/O Port
AD7769
FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The AD7769 is a complete, two-channel, 8-bit, analog I/O port.
It has versatile input and output signal conditioning features
that make it ideal for use in head-positioning servos in Winches-
ter disk systems. It is equally suitable for floppy disk microstep-
ping head positioning, other closed loop digital servo systems
and general purpose 8-bit data acquisition.
The AD7769 contains a high speed successive approximation
ADC, preceded by a two-channel multiplexer and signal condi-
tioning circuits. The input span of the ADC and the offset of
the zero point from ground can be independently set by apply-
ing ground referenced voltages. The AD7769 also contains two
independent, fast settling, 8-bit DACs with output amplifiers.
The output span and offset voltage of the DACs can be set inde-
pendently of those of the ADC. This makes the AD7769 espe-
cially useful in disk drives, where only a positive supply rail is
available and the ranges of the ADC and DACs must be refer-
enced to some positive voltage less than the supply.
The AD7769 is easily interfaced to a standard 8-bit mpu bus via
an 8-bit data port and standard microprocessor control lines.
The AD7769 is fabricated in Linear Compatible CMOS
(LC²MOS), an advanced, mixed technology process that com-
bines precision bipolar circuits with low power CMOS logic.
The part is available in a 28-lead plastic DIP and 28-terminal
PLCC package.
PRODUCT HIGHLIGHTS
1. Two-Channel, 8-Bit Analog I/O port on a Single Chip.
The AD7769 contains a two-channel, high speed ADC with
input signal conditioning and two, fast settling 8-bit DACs
with output amplifiers, on a single chip.
2. Independent Control of Span and Offset.
The input voltage span of the ADC and the midpoint of the
transfer function, the output voltage swing of the two DACs
and the half-scale output voltage, can be set independently
by applying ground referenced control voltages.
3. Dynamic Specifications for DSP Users.
In addition to the traditional ADC and DAC specifications,
the AD7769 is specified with ac parameters including signal-
to-noise ratio, distortion and signal bandwidth.
4. Fast Microprocessor Interface.
The AD7769 has bus interface timing compatible with all
modern microprocessors, with bus access and relinquish
times less than 65 ns and a Write pulse width less than 90 ns.
REV. A
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© Analog Devices, Inc., 1997