X9401_06 Datasheet, PDF (3/19 Pages) Intersil Corporation – Quad, 64 Tap, Digitally Controlled Potentiometer

X9401
PIN CONFIGURATION
SOIC
V_CC
V_L0/R_L0
V_H0/R_H0
V_W0/R_W0
CS
WP
SI
A₁
V_L1/R_L1
V_H1/R_H1
V_W1/R_W1
V _SS
1
24
2
23
3
22
4
21
5
20
6
19
X9401
7
18
8
17
9
16
10
15
11
14
12
13
NC
V_L3/R_L3
V_H3/R_H3
V_W3/R_W3
A₀
SO
HOLD
SCK
V_L2/R_L2
V_H2/R_H2
V_W2/R_W2
NC
PIN NAMES
Symbol
SCK
SI, SO
A₀ - A₁
V_H0/R_H0 - V_H3/R_H3,
V_L0/R_L0 - V_L3/R_L3
V_W0/R_W0 - V_W1/R_W1
WP
V_CC
V_SS
NC
Description
Serial Clock
Serial Data
Device Address
Potentiometers (terminal
equivalent)
Potentiometers (wiper
equivalent)
Hardware Write Protection
System Supply Voltage
System Ground
No Connection
DEVICE DESCRIPTION
The X9401 is a highly integrated microcircuit incorpo-
rating four resistor arrays and their associated regis-
ters and counters and the serial interface logic
providing direct communication between the host and
the XDCP potentiometers.
Serial Interface
The X9401 supports the SPI interface hardware con-
ventions. 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 X9401 is comprised of four resistor arrays. Each
array contains 63 discrete resistive segments that are
connected in series. The physical ends of each array
are equivalent to the fixed terminals of a mechanical
potentiometer (V_H/R_H and V_L/R_L inputs).
At both ends of each array and between each resistor
segment is a CMOS switch connected to the wiper
(V_W/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 six bits of the WCR are decoded
to select, and enable, one of sixty-four switches.
Wiper Counter Register (WCR)
The X9401 contains four Wiper Counter Registers,
one for each XDCP potentiometer. The WCR is equiv-
alent to a serial-in, parallel-out register/counter with its
outputs decoded to select one of sixty-four switches
along its resistor array. The contents of the WCR can
be altered in four ways: it may be written directly by
the host via the Write Wiper Counter Register instruc-
tion (serial load); it may be written indirectly by trans-
ferring the contents of one of four associated data
registers via the XFR Data Register or Global XFR
Data Register instructions (parallel load); it can be
modified one step at a time by the Increment/Decre-
ment instruction. Finally, it is loaded with the contents
of its data register zero (R0) upon power-up.
The Wiper Counter Register is a volatile register; that
is, its contents are lost when the X9401 is powered-
down. Although the register is automatically loaded
with the value in R₀ upon power-up, this may be differ-
ent from the value present at power-down. The wiper
position must be stored in R₀ to insure restoring the
wiper position after power-up.
Data Registers
Each potentiometer has four 6-bit nonvolatile data reg-
isters. These can be read or written directly by the
host. Data can also be transferred between any of the
four data registers and the associated Wiper Counter
Register. All operations changing data in one of the
data registers is a nonvolatile operation and will take a
maximum of 10ms.
If the application does not require storage of multiple
settings for the potentiometer, the data registers can
be used as memory locations for system parameters
or user preference data.
3
FN8190.3
October 12, 2006