X9259 Xicor, X9259 Datasheet - Page 5

• Manufacturer Part Number: X9259
• Description: Quad Digitally-Controlled (XDCP) Potentiometers
• Manufacturer: Xicor

X9259
PRINCIPLES OF OPERATION
The X9259 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 X9259 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
At both ends of each array and between each resistor
segment is a CMOS switch connected to the wiper
(R
switch may be turned on at a time.
Figure 1. Detailed Potentiometer Block Diagram
REV 1.2.3 4/30/02
IF WCR = 00[H] THEN R
IF WCR = FF[H] THEN R
One of Four Potentiometers
W
) output. Within each individual array only one
FROM INTERFACE
SERIAL DATA PATH
CIRCUITRY
W
W
= R
= R
L
REGISTER 0
REGISTER 2
H
(DR0)
(DR2)
H
and R
8
L
inputs).
REGISTER 1
REGISTER 3
MODIFIED SCL
(DR1)
(DR3)
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UP/DN
8
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 Recommendations.
There are no restrictions on the power-up or power-
down conditions of V
potentiometer pins provided that V
positive than or equal to V
V
effect.
L
, V
UP/DN
CLK
PARALLEL
BUS
INPUT
SERIAL
BUS
INPUT
W
REGISTER
COUNTER
. The V
INC/DEC
WIPER
LOGIC
(WCR)
CC
Characteristics subject to change without notice.
ramp rate specification is always in
C
O
U
N
T
E
R
D
E
C
O
D
E
CC
and the voltages applied to the
H
, V
L
, and V
CC
W
is always more
, i.e., V
R
R
R
H
L
W
CC
5 of 25
≥ V
H
,