X9111 Datasheet, PDF (3/18 Pages) Xicor Inc. – Single Digitally-Controlled Potentiometer

X9111
Pin Descriptions
PIN
(TSSOP)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SYMBOL
FUNCTION
SO
Serial Data Output
A0
Device Address
NC
No Connect
CS
Chip Select
SCK Serial Clock
SI
Serial Data Input
V_SS
System Ground
WP
Hardware Write Protect
A1
Device Address
HOLD Device Select. Pause the Serial Bus
R_W
R_H
R_L
V_CC
Wiper Terminal of the Potentiometer
High Terminal of the Potentiometer
Low Terminal of the Potentiometer
System Supply Voltage
Pin Descriptions
Bus Interface Pins
SERIAL OUTPUT (SO)
SO is a serial data output pin. During a read cycle, data is
shifted out on this pin. Data is clocked out by the falling edge
of the serial clock.
SERIAL INPUT (SI)
SI is the serial data input pin. All opcodes, byte addresses and
data to be written to the pots and pot registers are input on this
pin. Data is latched by the rising edge of the serial clock.
SERIAL CLOCK (SCK)
The SCK input is used to clock data into and out of the
X9111.
HOLD (HOLD)
HOLD is used in conjunction with the CS pin to select the
device. Once the part is selected and a serial sequence is
underway, HOLD may be used to pause the serial
communication with the controller without resetting the serial
sequence. To pause, HOLD must be brought LOW while SCK is
LOW. To resume communication, HOLD is brought HIGH, again
while SCK is LOW. If the pause feature is not used, HOLD should
be held HIGH at all times.
DEVICE ADDRESS (A₀, A₁)
The address inputs are used to set the 8-bit slave address. A
match in the slave address serial data stream must be made
with the address input (A1–A0) in order to initiate
communication with the X9111.
CHIP SELECT (CS)
When CS is HIGH, the X9111 is deselected and the SO pin is at
high impedance, and (unless an internal write cycle is
underway) the device will be in the standby state. CS LOW
enables the X9111, placing it in the active power mode. It
should be noted that after a power-up, a HIGH to LOW
transition on CS is required prior to the start of any operation.
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 is 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 (NC)
Pin should be left open. This pin is used for Intersil
manufacturing and test purposes.
Principles of Operation
Device Description
Serial Interface
The X9111 supports the SPI interface hardware conventions.
The device is accessed via the SI input with data clocked-in on
the rising SCK. CS must be LOW and the HOLD and WP pins
must be HIGH during the entire operation.
The SO and SI pins can be connected together, since they
have three state outputs. This can help to reduce system pin
count.
Array Description
The X9111 is comprised of a resistor array (see Figure 1).
The array contains the equivalent of 1023 discrete resistive
segments that are connected in series. 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 the individual array only one switch may be
turned on at a time.
3
FN8159.1
March 25, 2005