X9119 Datasheet, PDF (4/22 Pages) Xilinx, Inc – Single Digitally-Controlled (XDCP ™ ) Potentiometer

X9119 – Preliminary Information
PIN DESCRIPTIONS
Bus Interface Pins
SERIAL DATA INPUT/OUTPUT (SDA)
The SDA is a bidirectional serial data input/output pin
for a 2-wire slave device and is used to transfer data
into and out of the device. It receives device address,
opcode, wiper register address and data sent from an
2-wire master at the rising edge of the serial clock
SCL, and it shifts out data after each falling edge of the
serial clock SCL.
It is an open drain output and may be wire-ORed with
any number of open drain or open collector outputs. An
open drain output requires the use of a pull-up resistor.
For selecting typical values, refer to the guidelines for
calculating typical values on the bus pull-up resistors
graph.
SERIAL CLOCK (SCL)
This input is used by 2-wire master to supply 2-wire
serial clock to the X9119.
DEVICE ADDRESS (A₂–A₀)
The Address inputs are used to set the least significant
3 bits of the 8-bit slave address. A match in the slave
address serial data stream must be made with the
Address input in order to initiate communication with
the X9119. A maximum of 8 devices may occupy the 2-
wire serial bus.
Hardware Write Protect Input (WP)
The WP pin when LOW prevents nonvolatile writes to
the Data Registers.
Potentiometer Pins
R_H, R_L
The R_H and R_L pins are equivalent to the terminal
connections on a mechanical potentiometer.
R_W
The wiper pin are equivalent to the wiper terminal of a
mechanical potentiometer.
Bias Supply Pins
SYSTEM SUPPLY VOLTAGE (V_CC) AND SUPPLY GROUND (V_SS)
The V_CC pin is the system supply voltage. The V_SS pin
is the system ground.
Other Pins
NO CONNECT
No connect pins should be left open. These pins are
used for Xicor manufacturing and testing purposes.
PRINCIPLES OF OPERATION
The X9119 is an integrated microcircuit incorporating a
resistor array and its associated registers and counters
and the serial interface logic providing direct
communication between the host and the digitally
controlled potentiometer. This section provides detail
description of the following:
– Resistor Array Description
– Serial Interface Description
– Instruction and Register Description
Resistor Array Description
The X9119 is comprised of a resistor array. The array
contains, in effect, 1023 discrete resistive segments
that are connected in series (see Figure 1). The
physical ends of each array are equivalent to the fixed
terminals of a mechanical potentiometer (R_H and R_L
inputs).
At both ends of each array and between each resistor
segment is a CMOS switch connected to the wiper
(R_W) output. Within each individual array only one
switch may be turned on at a time. These switches are
controlled by the Wiper Counter Register (WCR). The
10-bits of the WCR (WCR[9:0]) are decoded to select,
and enable, one of 1024 switches.
The WCR may be written directly. The Data Registers
and the WCR can be read and written by the host
system.
REV 1.1.11 3/12/02
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Characteristics subject to change without notice. 4 of 22