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FN8170.3
August 29, 2006
standby state. CS LOW enables the X9260, 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.
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
S
YSTEM SUPPLY VOLTAGE (V
CC
) AND SUPPLY
G
ROUND (V
SS
)
The V
CC
pin is the system supply voltage. The V
SS
pin is the system ground.
Analog Supply Voltages (V+ and V
-)
These supplies are the analog voltage supplies for the
potentiometer. The V+ supply is tied to the wiper
switches while the V- supply is used to bias the
switches and the internal P+ substrate of the
integrated circuit. Both of these supplies set the
voltage limits of the potentiometer.
Other Pins
N
O CONNECT
No connect pins should be left floating. This pins are
used for Intersil manufacturing and testing purposes.
H
ARDWARE WRITE PROTECT INPUT (WP)
The WP
pin when LOW prevents nonvolatile writes to
the Data Registers.
PRINCIPLES OF OPERATION
Serial Interface
The X9260 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 X9260 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.
At all times, the voltages on the potentiometer pins
must be less than V+ and more than V-. During power-
up and power-down, VCC, V+, and V- must reach their
final values within 1msecs of each other. The V
CC
ramp rate spec is always in effect.
X9260
