®
X9401
Low Noise/Low Power/SPI Bus
Data Sheet
October 13, 2009
FN8190.4
Quad, 64 Tap, Digitally Controlled
Potentiometer (XDCP™)
Description
The X9401 integrates 4 digitally controlled potentiometers
(XDCP) on a monolithic CMOS integrated microcircuit.
The digitally controlled potentiometer is implemented using
64 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 4 nonvolatile Data Registers
(DR0:DR3) 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 through the switches. Power-up
recalls the contents of 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.
Features
• Quad - 4 Separate Pots, 64 Taps/Pot
• Nonvolatile Storage of Wiper Position
• Four Nonvolatile Data Registers for Each Pot
• 16-bytes of EEPROM Memory
• SPI Serial Interface
• R
TOTAL
= 10kΩ
• Wiper Resistance = 150Ω Typical
• Standby Current < 3µA (Total Package)
• Operating Current < 700µA max.
• V
CC
= 2.7V to 5V
• 24 Ld SOIC and 24 Ld TSSOP Package
• 100 year Data Retention
• Pb-Free Available (RoHS Compliant)
Block Diagram
V
CC
V
SS
R0
R1
POT 0
WIPER
COUNTER
REGISTER
(WCR)
V
H0
/R
H0
R0
R1
WIPER
COUNTER
REGISTER
(WCR)
V
H2
/R
H2
HOLD
CS
SCK
SO
SI
A0
A1
WP
INTERFACE
AND
CONTROL
CIRCUITRY
DATA
R2
R3
V
L0
/R
L0
V
W0
/R
W0
R2
R3
RESISTOR
ARRAY
POT 2
V
L2
/R
L2
V
W2
/R
W2
8
V
W1
/R
W1
R0
R1
WIPER
COUNTER
REGISTER
(WCR)
V
H1
/R
H1
R0
R1
V
W3
/R
W3
WIPER
COUNTER
REGISTER
(WCR)
V
H3
/R
H3
RESISTOR
ARRAY
POT 1
R2
R3
V
L1
/R
L1
R2
R3
RESISTOR
ARRAY
POT 3
V
L3
/R
L3
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, 2009. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
X9401
Ordering Information
PART
NUMBER
X9401WS24IZ* (Note 1)
X9401WS24I
X9401WS24Z* (Note 1)
X9401WV24IZ* (Note 1)
X9401WV24Z* (Note 1)
PART
MARKING
X9401WS ZI
X9401WS I
X9401WS Z
X9401WV ZI
X9401WV Z
2.7 to 5.5
V
CC
LIMITS
(V)
5 ±10%
POTENTIOMETER
ORGANIZATION
(kΩ)
10
TEMP
RANGE
(°C)
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-40 to +85
PACKAGE
24 Ld SOIC (300 mil) (Pb-free)
24 Ld SOIC (300 mil)
24 Ld SOIC (300 mil)
PKG.
DWG. #
M24.3
M24.3
M24.3
24 Ld TSSOP (4.4mm) (Pb-free) MDP0044
24 Ld TSSOP (4.4mm) (Pb-free) MDP0044
24 Ld SOIC (300 mil)
24 Ld SOIC (300 mil) (Pb-free)
24 Ld SOIC (300 mil) (Pb-free)
24 Ld TSSOP (4.4mm)
M24.3
M24.3
M24.3
MDP0044
X9401WS24I-2.7* (Note 2) X9401WS G
X9401WS24IZ-2.7* (Note)
X9401WS ZG
X9401WS24Z-2.7* (Note 1) X9401WS ZF
X9401WV24-2.7
X9401WV F
X9401WV24IZ-2.7* (Note 1) X9401WV ZG
X9401WV24Z-2.7* (Note 1) X9401WV ZF
NOTES:
24 Ld TSSOP (4.4mm) (Pb-free) MDP0044
24 Ld TSSOP (4.4mm) (Pb-free) MDP0044
*Add “T1” suffix for tape and reel. Please refer to TB347 for details on reel specifications.
1. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100%
matte tin plate plus anneal (e3 termination finish, which is 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.
2. Not recommended for new designs.
Pin Descriptions
Host Interface Pins
SERIAL OUTPUT (SO)
SO is a push/pull 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.
SERIAL INPUT
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.
SERIAL CLOCK (SCK)
The SCK input is used to clock data into and out of the
X9401.
CHIP SELECT (CS)
When CS is HIGH, the X9401 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 X9401, 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.
HOLD (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.
DEVICE ADDRESS (A
0
-
A
1
)
The address inputs are used to set the least significant 2 bits of the
8-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 X9401. A maximum of 4
devices may occupy the SPI serial bus.
Potentiometer Pins
V
H
(V
H0
- V
H3
)/ R
H
(R
H0
- R
H3
),
V
L
(V
L0
- V
L3
)/R
L
(R
L0
- R
L3
)
The V
H
/R
H
and V
L
/R
L
inputs are equivalent to the terminal
connections on either end of a mechanical potentiometer.
VW (VW0 - VW3)/ RW (RW0 - RW3)
The wiper outputs are equivalent to the wiper output of a
mechanical potentiometer.
HARDWARE WRITE PROTECT INPUT (WP)
The WP pin when LOW prevents nonvolatile writes to the
Wiper Counter Registers.
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FN8190.4
October 13, 2009
X9401
Pinouts
X9401
(24 LD SOIC)
TOP VIEW
V
CC
1
V
L0
/R
L0
2
V
H0
/R
H0
3
V
W0
/R
W0
4
CS 5
WP 6
SI 7
A
1
8
V
L1
/R
L1
9
V
H1
/R
H1
10
V
W1
/R
W1
11
V
SS
12
24 NC
23 V
L3
/R
L3
22 V
H3
/R
H3
21 V
W3
/R
W3
20 A
0
19 S0
18 HOLD
17 SCK
16 V
L2
/R
L2
15 V
H2
/R
H2
14 V
W2
/R
W2
13 NC
Device Description
The X9401 is a highly 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 XDCP
potentiometers.
Serial Interface
The X9401 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.
X9401
(24 LD TSSOP)
TOP VIEW
SI 1
A
1
2
V
L1
/R
L1
3
V
H1
/R
H1
4
V
W1
/R
W1
5
V
SS
6
NC 7
V
W2
/R
W2
8
V
H2
/R
H2
9
V
L2
/R
L2
10
SCK 11
HOLD 12
24 WP
23 CS
22 V
W0
/R
W0
21 V
H0
/R
H0
20 V
L0
/R
L0
19 V
CC
18 NC
17 V
L3
/R
L3
16 V
H3
/R
H3
15 V
W3
/R
W3
14 A
0
13 S0
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 equivalent 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 instruction (serial load); it may be written
indirectly by transferring 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/Decrement
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 R
0
upon power-up, this may be different from the value
present at power-down. The wiper position must be stored in
R
0
to insure restoring the wiper position after power-up.
Pin Descriptions
SOIC TSSOP
PIN # PIN #
5
17
7, 19
20, 8
23
11
1, 13
14, 2
SYMBOL
CS
SCK
SI, S0
A
0
- A
1
DESCRIPTION
Chip select
Serial Clock
Serial Data
Device Address
3, 10, 21, 4,
15, 22, 9, 16,
20, 3,
2, 9,
16, 23 10, 17
4, 11,
14, 21
6
18
1
12
13, 24
22, 5,
8, 15
24
12
19
6
7, 18
V
H0
/R
H0,
V
H1
/R
H1,
Potentiometer end
V
H2
/R
H2
, V
H3
/R
H3
, terminals
V
L0
/R
L0,
V
L1
/R
L1
,
V
L2
/R
L2,
V
L3
/R
L3
V
W0
/R
W0,
V
W1
/R
W1,
Wipers
V
W2
/R
W2,
V
W3
/R
W3
WP
HOLD
V
CC
V
SS
NC
Hardware Write Protection
Hardware Hold
System Supply Voltage
System Ground
No Connection
3
FN8190.4
October 13, 2009
X9401
Data Registers
Each potentiometer has four 6-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 memory locations for system parameters or user
preference data.
DATA REGISTER DETAIL
FIGURE 2. IDENTIFICATION BYTE FORMAT
(MSB)
D5
NV
D4
NV
D3
NV
D2
NV
D1
NV
(LSB)
D0
NV
Instruction Byte
The next byte sent to the X9401 contains the instruction and
register pointer information. The four most significant bits are
the instruction. The next four bits point to one of the four pots
and, when applicable, they point to one of four associated
registers. The format is shown below in Figure 2.
I
I3
I2
I1
I0
R1
R0
P1
P0
INSTRUCTIONS
POT SELECT
Write in Process
The contents of the Data Registers are saved to nonvolatile
memory when the CS pin goes from LOW to HIGH after a
complete write sequence is received by the device. The
progress of this internal write operation can be monitored by
a Write In Process bit (WIP). The WIP bit is read with a Read
Status command.
The four high order bits of the instruction byte specify the
operation. The next two bits (R
1
and R
0
) select one of the
four registers that is to be acted upon when a register
oriented instruction is issued. The last two bits (P1 and P
0
)
selects which one of the four potentiometers is to be affected
by the instruction.
Four of the ten instructions are two bytes in length and end
with the transmission of the instruction byte. These
instructions are:
• XFR Data Register to Wiper Counter Register: This
transfers the contents of one specified Data Register to
the associated Wiper Counter Register.
• XFR Wiper Counter Register to Data Register: This
transfers the contents of the specified Wiper Counter
Register to the specified associated Data Register.
• Global XFR Data Register to Wiper Counter Register: This
transfers the contents of all specified Data Registers to the
associated Wiper Counter Registers.
• Global XFR Wiper Counter Register to Data
Register: This transfers the contents of all Wiper Counter
Registers to the specified associated Data Registers.
The basic sequence of the two byte instructions is illustrated
in Figure 3. These two-byte instructions exchange data
between the WCR and one of the data registers. A transfer
from a data register to a WCR is essentially a write to a static
RAM, with the static RAM controlling the wiper position. The
response of the wiper to this action will be delayed by t
WRL
.
A transfer from the WCR (current wiper position), to a data
register is a write to nonvolatile memory and takes a
minimum of t
WR
to complete. The transfer can occur
between one of the four potentiometers and one of its
associated registers; or it may occur globally, where the
transfer occurs between all potentiometers and one
associated register.
Five instructions require a three-byte sequence to complete.
These instructions transfer data between the host and the
X9401; either between the host and one of the data registers
Instructions
Identification (ID) Byte
The first byte sent to the X9401 from the host, following a CS
going HIGH to LOW, is called the Identification byte. The
most significant four bits of the slave address are a device
type identifier. For the X9401 this is fixed as 0101[B] (refer to
Figure 1).
The two least significant bits in the ID byte select one of four
devices on the bus. The physical device address is defined
by the state of the A
0
- A
1
input pins. The X9401 compares
the serial data stream with the address input state; a
successful compare of both address bits is required for the
X9401 to successfully continue the command sequence.
The A
0
- A
1
inputs can be actively driven by CMOS input
signals or tied to V
CC
or V
SS
. The remaining two bits in the
slave byte must be set to 0.
DEVICE TYPE
IDENTIFIER
0
1
0
1
0
0
A1
A0
DEVICE ADDRESS
FIGURE 1. IDENTIFICATION BYTE FORMAT
4
FN8190.4
October 13, 2009
X9401
or directly between the host and the Wiper Counter Register.
These instructions are:
• Read Wiper Counter Register: read the current wiper
position of the selected pot,
• Write Wiper Counter Register: change current wiper
position of the selected pot,
• Read Data Register: read the contents of the selected
data register;
• Write Data Register: write a new value to the selected data
register.
• Read Status: This command returns the contents of the
WIP bit which indicates if the internal write cycle is in
progress.
The sequence of these operations is shown in Figure 4 and
Figure 5.
The final command is Increment/Decrement. It is different
from the other commands, because it’s length is
indeterminate. Once the command is issued, the master can
clock the selected wiper up and/or down in one resistor
segment steps; thereby, providing a fine tuning capability to
the host. For each SCK clock pulse (t
HIGH
) while SI is HIGH,
the selected wiper will move one resistor segment towards
the V
H
/R
H
terminal. Similarly, for each SCK clock pulse
while SI is LOW, the selected wiper will move one resistor
segment towards the V
L
/R
L
terminal. A detailed illustration of
the sequence and timing for this operation are shown in
Figure 6 and Figure 7.
Detailed Potentiometer Block Diagram
(ONE OF FOUR ARRAYS)
SERIAL DATA PATH
FROM INTERFACE
CIRCUITRY
REGISTER 0
REGISTER 1
SERIAL
BUS
INPUT
C
O
U
N
T
E
R
D
E
C
O
D
E
V
H
/R
H
8
6
PARALLEL
BUS
INPUT
WIPER
COUNTER
REGISTER
(WCR)
REGISTER 2
REGISTER 3
IF WCR = 00[H] THEN V
W
/R
W
= V
L
/R
L
IF WCR = 3F[H] THEN V
W
/R
W
= V
H
/R
H
INC/DEC
LOGIC
UP/DN
MODIFIED SCL
UP/DN
CLK
V
L
/R
L
V
W
/R
W
5
FN8190.4
October 13, 2009
Embedded System
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