X9261 Datasheet, PDF (5/21 Pages) Intersil Corporation – Single Supply/Low Power/256-Tap/SPI Bus

X9261
Potentiometer Pins
R_H, R_L
The R_H and R_L pins are equivalent to the terminal
connections on a mechanical potentiometer. Since
there are 2 potentiometers, there are 2 sets of R_H and
R_L such that R_H0 and R_L0 are the terminals of POT 0
and so on.
R_W
The wiper pin are equivalent to the wiper terminal of a
mechanical potentiometer. Since there are 2
potentiometers, there are 2 sets of R_W such that R_W0
is the terminals of POT 0 and so on.
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 floating. This pins are
used for Intersil manufacturing and testing purposes.
HARDWARE WRITE PROTECT INPUT (WP)
The WP pin when LOW prevents nonvolatile writes to
the Data Registers.
PRINCIPLES OF OPERATION
Serial Interface
The X9261 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 X9261 is comprised of a resistor array (See
Figure 1). The array contains the equivalent of 255
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 each individual array only one
switch may be turned on at a time.
These switches are controlled by a Wiper Counter
Register (WCR). The 8-bits of the WCR (WCR[7:0])
are decoded to select, and enable, one of 256
switches (See Table 1).
Power-up and Down Requirements.
There are no restrictions on the power-up or power-
down conditions of V_CC and the voltages applied to
the potentiometer pins provided that V_CC is always
more positive than or equal to V_H, V_L, and V_W, i.e.,
V_CC, V_H, V_L, V_W. The V_CC ramp rate specification is
always in effect.
5
FN8171.2
September 14, 2005