X9261
T
ODUC
TE PR
D UC T
BSOLE TITUTE PRO
O
Data Sheet
S UB S
SIBLE ISL22424
OS
P
Single Supply/Low Power/256-Tap/SPI Bus
October 12, 2006
FN8171.4
Dual Digitally-Controlled (XDCP™)
Potentiometers
FEATURES
• Dual–Two Separate Potentiometers
• 256 Resistor Taps/pot–0.4% Resolution
• SPI Serial Interface for Write, Read, and Transfer
Operations of the Potentiometer Single Supply
Device
• Wiper Resistance, 100 typical @ V
CC
= 5V
• 4 Nonvolatile Data Registers for Each
Potentiometer
• Nonvolatile Storage of Multiple Wiper Positions
• Power-on Recall Loads Saved Wiper Position on
Power-up.
• Standby Current < 5µA Max
• 50k, 100k Versions of End to End Resistance
• 100 yr. Data Retention
• Endurance: 100,000 Data Changes per Bit per
Register
• 24 Ld SOIC, 24 Ld TSSOP
• Low Power CMOS
• Power Supply V
CC
= 5V ±10%
• Pb-Free Plus Anneal Available (RoHS Compliant)
FUNCTIONAL DIAGRAM
V
CC
DESCRIPTION
The X9261 integrates 2 digitally controlled
potentiometer (XDCP) on a monolithic CMOS
integrated circuit.
The digital controlled potentiometer is implemented
using 255 resistive elements in a series array.
Between each element are tap points connected to the
wiper terminal through switches. The position of the
wiper on the array is controlled by the user through the
SPI bus interface. Each potentiometer has associated
with it a volatile Wiper Counter Register (WCR) and
four non-volatile Data Registers that can be directly
written to and read by the user. The contents of the
WCR controls the position of the wiper on the resistor
array though the switches. Powerup recalls the
contents of the default Data Register (DR0) to the
WCR.
The XDCP can be used as a three-terminal
potentiometer or as a two terminal variable resistor in
a wide variety of applications including control,
parameter adjustments, and signal processing.
R
H0
R
H1
SPI
Bus
Interface
Address
Data
Status
Write
Read
Transfer
Inc/Dec
Bus
Interface
and Control
Control
Power-on Recall
Wiper Counter
Register (WCR)
Data Registers
(DR0-DR3)
V
SS
R
W0
R
L0
R
W1
R
L1
50k or 100k versions
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
|
Intersil (and design) is a registered trademark of Intersil Americas Inc.
XDCP is a trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2005, 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
X9261
Ordering Information
PART NUMBER
X9261US24
X9261US24Z (Note)
X9261UV24
X9261UV24Z (Note)
PART
MARKING
X9261US
X9261US Z
X9261UV
X9261UV Z
V
CC
LIMITS
(V)
R
TOTAL
(k) TEMP RANGE (°C)
5 ±10%
50
0 to 70
0 to 70
0 to 70
0 to 70
PACKAGE
24 Ld SOIC (300 mil)
24 Ld SOIC (300 mil) (Pb-free)
24 Ld TSSOP (4.4mm)
24 Ld TSSOP (4.4mm) (Pb-free)
PKG.
DWG. #
M24.3
M24.3
MDP0044
MDP0044
NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
DETAILED FUNCTIONAL DIAGRAM
R
H0
R
L0
R
W0
V
CC
Power-on
Recall
HOLD
CS
SCK
SO
SI
A0
A1
INTERFACE
AND
CONTROL
CIRCUITRY
8
WP
Data
Power-on
Recall
R
0
R
1
Wiper
Counter
Register
(WCR)
Resistor
Array
Pot 1
R
0
R
1
Wiper
Counter
Register
(WCR)
Pot 0
R
2
R
3
50k and 100k
256-taps
R
2
R
3
V
SS
R
L1
R
H1
R
W1
CIRCUIT LEVEL APPLICATIONS
• Vary the gain of a voltage amplifier
• Provide programmable dc reference voltages for
comparators and detectors
• Control the volume in audio circuits
• Trim out the offset voltage error in a voltage amplifier
circuit
• Set the output voltage of a voltage regulator
• Trim the resistance in Wheatstone bridge circuits
• Control the gain, characteristic frequency and
Q-factor in filter circuits
• Set the scale factor and zero point in sensor signal
conditioning circuits
• Vary the frequency and duty cycle of timer ICs
• Vary the dc biasing of a pin diode attenuator in RF
circuits
• Provide a control variable (I, V, or R) in feedback
circuits
2
FN8171.4
October 12, 2006
X9261
SYSTEM LEVEL APPLICATIONS
• Adjust the contrast in LCD displays
• Control the power level of LED transmitters in
communication systems
• Set and regulate the DC biasing point in an RF
power amplifier in wireless systems
• Control the gain in audio and home entertainment
systems
• Provide the variable DC bias for tuners in RF wire-
less systems
• Set the operating points in temperature control
systems
• Control the operating point for sensors in industrial
systems
• Trim offset and gain errors in artificial intelligent
systems
PIN CONFIGURATION
SOIC/TSSOP
SO
A0
NC
NC
NC
NC
V
CC
R
L0
R
H0
R
W0
CS
WP
1
2
3
4
5
6
7
8
9
10
11
12
X9261
24
23
22
21
20
19
18
17
16
15
14
13
HOLD
SCK
NC
NC
NC
NC
V
SS
R
W1
R
H1
R
L1
A1
SI
PIN ASSIGNMENTS
Pin
(SOIC/
TSSOP)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Symbol
SO
A0
NC
NC
NC
NC
V
CC
R
L0
R
H0
R
W0
CS
WP
SI
A1
R
L1
R
H1
R
W1
V
SS
NC
NC
NC
NC
SCK
HOLD
Function
Serial Data Output for SPI bus
Device Address for SPI bus.
No Connect.
No Connect.
No Connect.
No Connect.
System Supply Voltage
Low Terminal for Potentiometer 0.
High Terminal for Potentiometer 0.
Wiper Terminal for Potentiometer 0.
Device Address for SPI bus.
Hardware Write Protect
Serial Data Input for SPI bus
Device Address for SPI bus.
Low Terminal for Potentiometer 1.
High Terminal for Potentiometer 1.
Wiper Terminal for Potentiometer 1.
System Ground
No Connect
No Connect
No Connect
No Connect
Serial Clock for SPI bus
Device select. Pause the SPI serial bus.
PIN DESCRIPTIONS
Bus Interface Pins
S
ERIAL
O
UTPUT
(SO)
SO is a serial data output pin. During a read cycle,
data is shifted out on this pin. Data is clocked out by
the falling edge of the serial clock.
S
ERIAL
I
NPUT
SI is the serial data input pin. All opcodes, byte
addresses and data to be written to the pots and pot
registers are input on this pin. Data is latched by the
rising edge of the serial clock.
S
ERIAL
C
LOCK
(SCK)
The SCK input is used to clock data into and out of the
X9261.
3
FN8171.4
October 12, 2006
X9261
H
OLD
(HOLD)
HOLD is used in conjunction with the CS pin to select
the device. Once the part is selected and a serial
sequence is underway, HOLD may be used to pause
the serial communication with the controller without
resetting the serial sequence. To pause, HOLD must
be brought LOW while SCK is LOW. To resume
communication, HOLD is brought HIGH, again while
SCK is LOW. If the pause feature is not used, HOLD
should be held HIGH at all times.
D
EVICE
A
DDRESS
(A1 - A0)
The address inputs are used to set the 4-bit slave
address. A match in the slave address serial data
stream must be made with the address input in order
to initiate communication with the X9261.
C
HIP
S
ELECT
(CS)
When CS is HIGH, the X9261 is deselected and the
SO pin is at high impedance, and (unless an internal
write cycle is underway) the device will be in the
standby state. CS LOW enables the X9261, 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
S
UPPLY
V
OLTAGE
(V
CC
)
AND
S
UPPLY
G
ROUND
(V
SS
)
The V
CC
pin is the system supply voltage. The V
SS
pin is the system ground.
Other Pins
N
O
C
ONNECT
No connect pins should be left floating. This pins are
used for Intersil manufacturing and testing purposes.
H
ARDWARE
W
RITE
P
ROTECT
I
NPUT
(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.
4
FN8171.4
October 12, 2006
X9261
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)
SERIAL
BUS
INPUT
C
O
U
N
T
E
R
D
E
C
O
D
E
R
H
REGISTER 2
(DR2)
REGISTER 3
(DR3)
IF WCR = 00[H] THEN R
W
= R
L
IF WCR = FF[H] THEN R
W
= R
H
INC/DEC
LOGIC
UP/DN
MODIFIED SCK
UP/DN
CLK
R
L
R
W
DEVICE DESCRIPTION
Wiper Counter Register (WCR)
The X9261 contains two Wiper Counter Registers, one
for each DCP potentiometer. The Wiper Counter
Register can be envisioned as a 8-bit parallel and
serial load counter with its outputs decoded to select
one of 256 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 instruction (serial load); it may be
written indirectly by transferring the contents of one of
four associated data registers via the XFR Data
Register instruction (parallel load); it can be modified
one step at a time by the Increment/Decrement
instruction (See Instruction section for more details).
Finally, it is loaded with the contents of its Data
Register zero (DR0) upon power-up.
The Wiper Counter Register is a volatile register; that
is, its contents are lost when the X9261 is powered-
down. Although the register is automatically loaded
with the value in DR0 upon power-up, this may be
different from the value present at power-down.
Power-up guidelines are recommended to ensure
proper loadings of the DR0 value into the WCR.
Data Registers (DR)
Each potentiometer has four 8-bit nonvolatile Data
Registers. 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 regular memory locations for system
parameters or user preference data.
Bits [7:0] are used to store one of the 256 wiper
positions or data (0~255).
Status Register (SR)
This 1-bit Status Register is used to store the system
status.
WIP: Write In Progress status bit, read only.
– When WIP=1, indicates that high-voltage write cycle
is in progress.
– When WIP=0, indicates that no high-voltage write
cycle is in progress.
5
FN8171.4
October 12, 2006
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