X9269
PRINCIPLES OF OPERATION
The X9269 is a integrated microcircuit incorporating
four resistor arrays and their associated registers and
counters and the serial interface logic providing direct
communication between the host and the digitally
controlled potentiometers. This section provides detail
description of the following:
– Resistor Array Description
– Serial Interface Description
– Instruction and Register Description.
Array Description
The X9269 is comprised of a resistor array (see Figure
1). Each array contains 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.
Figure 1. Detailed Potentiometer Block Diagram
One of Two Potentiometers
SERIAL DATA PATH
FROM INTERFACE
CIRCUITRY
REGISTER 0
(DR0)
8
REGISTER 1
(DR1)
8
PARALLEL
BUS
INPUT
WIPER
COUNTER
REGISTER
(WCR)
INC/DEC
LOGIC
UP/DN
MODIFIED SCL
UP/DN
CLK
R
L
SERIAL
BUS
INPUT
C
O
U
N
T
E
R
D
E
C
O
D
E
R
H
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).
The WCR may be written directly. These Data
Registers can the WCR can be read and written by the
host system.
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.
REGISTER 2
(DR2)
REGISTER 3
(DR3)
IF WCR = 00[H] THEN R
W
= R
L
IF WCR = FF[H] THEN R
W
= R
H
R
W
REV 1.1.11 2/17/03
www.xicor.com
Characteristics subject to change without notice.
5 of 25
XICOR [ XICOR INC. ]
