APPLICATION NOTE
A V A I L A B L E
AN20 • AN42–53 • AN71 • AN73 • AN88 • AN91–92 • AN99 • AN115 • AN120 • AN124 • AN133 • AN134 • AN135
Low Noise, Low Power, 32 Taps
X9315
Digitally Controlled Potentiometer (XDCP™)
FEATURES
DESCRIPTION
• Solid-state potentiometer
• 3-wire serial interface
• 32 wiper tap points
—Wiper position stored in nonvolatile memory
and recalled on power-up
• 31 resistive elements
—Temperature compensated
—End to end resistance range ± 20%
—Terminal voltage, 0 to VCC
• Low power CMOS
—VCC = 2.7V or 5V
—Active current, 50/400µA max.
—Standby current, 1µA max.
• High reliability
—Endurance, 100,000 data changes per bit
—Register data retention, 100 years
• RTOTAL values = 10KΩ, 50KΩ, 100KΩ
• Packages
—8-lead SOIC, MSOP and DIP
The Xicor X9315 is a digitally controlled potentiometer
(XDCP). The device consists of a resistor array, wiper
switches, a control section, and nonvolatile memory.
The wiper position is controlled by a 3-wire interface.
The potentiometer is implemented by a resistor array
composed of 31 resistive elements and a wiper
switching network. Between each element and at
either end are tap points accessible to the wiper
terminal. The position of the wiper element is
controlled by the CS, U/D, and INC inputs. The
position of the wiper can be stored in nonvolatile
memory and then be recalled upon a subsequent
power-up operation.
The device 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
– signal processing
BLOCK DIAGRAM
U/D
INC
CS
VCC (Supply Voltage)
Control
and
Memory
Device Select
(CS)
RH/VH
31
30
29
RH/VH
Up/Down
(U/D)
Increment
(INC)
5-Bit
Up/Down
Counter
5-Bit
Nonvolatile
Memory
RW/VW
RL/VL
28
One
of
Thirty
Two
Decoder
Transfer
Gates
Resistor
Array
2
VSS (Ground)
General
VCC
VSS
Store and
Recall
Control
Circuitry
1
0
RL/VL
RW/VW
Detailed
XDCP™ is a trademark of Xicor, Inc.
REV 1.3.2 1/14/03
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Characteristics subject to change without notice.
1 of 13
X9315
PIN DESCRIPTIONS
PIN NAMES
RH/VH and RL/VL
The high (RH/VH) and low (RL/VL) terminals of the
X9315 are equivalent to the fixed terminals of a
mechanical potentiometer. The minimum voltage is
VSS and the maximum is VCC. The terminology of RL/
VL and RH/VH references the relative position of the
terminal in relation to wiper movement direction
selected by the U/D input, and not the voltage potential
on the terminal.
Symbol
RW/VW
RW/Vw is the wiper terminal and is equivalent to the
movable terminal of a mechanical potentiometer. The
position of the wiper within the array is determined by
the control inputs. The wiper terminal series resistance
is typically 200Ω at VCC = 5V.
Up/Down (U/D)
The U/D input controls the direction of the wiper
movement and whether the counter is incremented or
decremented.
Increment (INC)
The INC input is negative-edge triggered. Toggling
INC will move the wiper and either increment or
decrement the counter in the direction indicated by the
logic level on the U/D input.
Chip Select (CS)
The device is selected when the CS input is LOW. The
current counter value is stored in nonvolatile memory
when CS is returned HIGH while the INC input is also
HIGH. After the store operation is complete the X9315
will be placed in the low power standby mode until the
device is selected once again.
PIN CONFIGURATION
DIP/SOIC/MSOP
INC
1
8
VCC
U/D
RH/VH
2
7
6
CS
RL/VL
VSS
4
5
RW/VW
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X9315
Description
RH/VH
High terminal
RW/VW
Wiper terminal
RL/VL
Low terminal
VSS
Ground
VCC
Supply voltage
U/D
Up/Down control input
INC
Increment control input
CS
Chip Select control input
PRINCIPLES OF OPERATION
There are three sections of the X9315: the input
control, counter and decode section; the nonvolatile
memory; and the resistor array. The input control
section operates just like an up/down counter. The
output of this counter is decoded to turn on a single
electronic switch connecting a point on the resistor
array to the wiper output. Under the proper conditions
the contents of the counter can be stored in nonvolatile
memory and retained for future use. The resistor array
is comprised of 31 individual resistors connected in
series. At either end of the array and between each
resistor is an electronic switch that transfers the
connection at that point to the wiper.
The wiper, when at either fixed terminal, acts like its
mechanical equivalent and does not move beyond the
last position. That is, the counter does not wrap
around when clocked to either extreme.
The electronic switches on the device operate in a
“make before break” mode when the wiper changes
tap positions. If the wiper is moved several positions,
multiple taps are connected to the wiper for tIW (INC to
VW change). The RTOTAL value for the device can
temporarily be reduced by a significant amount if the
wiper is moved several positions.
When the device is powered-down, the last wiper
position stored will be maintained in the nonvolatile
memory. When power is restored, the contents of the
memory are recalled and the wiper is set to the value
last stored.
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Characteristics subject to change without notice.
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X9315
INSTRUCTIONS AND PROGRAMMING
MODE SELECTION
The INC, U/D and CS inputs control the movement of
the wiper along the resistor array. With CS set LOW
the device is selected and enabled to respond to the
U/D and INC inputs. HIGH to LOW transitions on INC
will increment or decrement (depending on the state of
the U/D input) a five bit counter. The output of this
counter is decoded to select one of thirty two wiper
positions along the resistive array.
The value of the counter is stored in nonvolatile
memory whenever CS transitions HIGH while the INC
input is also HIGH.
CS
INC
Mode
U/D
L
H
Wiper Up
L
L
Wiper Down
H
X
Store Wiper Position
X
X
Standby Current
L
X
No Store, Return to Standby
H
SYMBOL TABLE
The system may select the X9315, move the wiper
and deselect the device without having to store the
latest wiper position in nonvolatile memory. After the
wiper movement is performed as described above and
once the new position is reached, the system must
keep INC LOW while taking CS HIGH. The new wiper
position will be maintained until changed by the
system or until a power-up/down cycle recalled the
previously stored data.
This procedure allows the system to always power-up
to a preset value stored in nonvolatile memory; then
during system operation minor adjustments could be
made. The adjustments might be based on user
preference, system parameter changes due to
temperature drift, etc...
WAVEFORM
INPUTS
OUTPUTS
Must be
steady
Will be
steady
May change
from Low to
High
Will change
from Low to
High
May change
from High to
Low
Will change
from High to
Low
Don’t Care:
Changes
Allowed
N/A
Changing:
State Not
Known
Center Line
is High
Impedance
The state of U/D may be changed while CS remains
LOW. This allows the host system to enable the device
and then move the wiper up and down until the proper
trim is attained.
REV 1.3.2 1/14/03
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Characteristics subject to change without notice.
3 of 13
X9315
ABSOLUTE MAXIMUM RATINGS
COMMENT
Temperature under bias ....................–65°C to +135°C
Storage temperature .........................–65°C to +150°C
Voltage on CS, INC, U/D, VH, VL and
VCC with respect to VSS ......................... –1V to +7V
∆V = |VH–VL|........................................................... 5V
Lead temperature (soldering 10 seconds)..........300°C
IW (10 seconds) .............................................. ±7.5mA
Stresses above those listed under “Absolute Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only; the functional operation of
the device (at these or any other conditions above
those listed in the operational sections of this
specification) is not implied. Exposure to absolute
maximum rating conditions for extended periods may
affect device reliability.
RECOMMENDED OPERATING CONDITIONS
Temperature
Min.
Max.
Supply Voltage (VCC)
Limits
Commercial
0°C
+70°C
X9315
5V ±10%
Industrial
–40°C
+85°C
X9315-2.7
2.7V to 5.5V
POTENTIOMETER CHARACTERISTICS (Over recommended operating conditions unless otherwise stated.)
Limits
Symbol
Parameter
Min.
Typ.
End to end resistance tolerance
Max.
Unit
±20
%
VVH
VH terminal voltage
0
VCC
V
VVL
VL terminal voltage
0
VCC
V
10
mW
Power rating
Test Conditions/Notes
RTOTAL ≥ 10 KΩ
RW
Wiper resistance
200
400
Ω
IW = 1mA, VCC = 5V
RW
Wiper resistance
400
1000
Ω
IW = 1mA, VCC = 2.7V
IW
Wiper current
±3.75
mA
Noise
Resolution
-120
dBV
3
%
Absolute linearity(1)
Relative
linearity(2)
RTOTAL temperature coefficient
CH/CL/CW
Potentiometer capacitances
±1
MI(3)
Vw(n)(actual)–Vw(n)(expected)
±0.2
MI(3)
Vw(n+1)–[Vw(n)+MI]
±300
Ratiometric temperature coefficient
ppm/°C
±20
10/10/25
Ref: 1kHz
ppm/°C
pF
See circuit #3
Notes: (1) Absolute linearity is utilized to determine actual wiper voltage versus expected voltage = (V w(n)(actual)–Vw(n)(expected)) = ±1 Ml
Maximum.
(2) Relative linearity is a measure of the error in step size between taps = RW(n+1)—[Rw(n) + Ml] = ±0.2 Ml.
(3) 1 Ml = Minimum Increment = RTOT/31.
(4) Typical values are for TA = 25°C and nominal supply voltage.
(5) This parameter is periodically sampled and not 100% tested
REV 1.3.2 1/14/03
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X9315
D.C. OPERATING CHARACTERISTICS (Over recommended operating conditions unless otherwise specified.)
Limits
Symbol
Parameter
Typ.(4)
Min.
Max.
Unit
Test Conditions
ICC1
VCC active current (Increment)
50
µA
CS = VIL, U/D = VIL or VIH and
INC = 0.4V @ max. tCYC
ICC2
VCC active current (Store) (EEPROM Store)
400
µA
CS = VIH, U/D = VIL or VIH and
INC = VIH @ max. tWR
ISB
Standby supply current
1
µA
CS = VCC – 0.3V, U/D and
INC = VSS or VCC – 0.3V
ILI
CS, INC, U/D input leakage
current
±10
µA
VIN = VSS to VCC
VIH
CS, INC, U/D input HIGH voltage
VCC x 0.7
VCC + 0.5
V
VIL
CS, INC, U/D input LOW voltage
–0.5
VCC x 0.1
V
CIN(5)
CS, INC, U/D input capacitance
10
pF
VCC = 5V, VIN = VSS,
TA = 25°C, f = 1MHz
ENDURANCE AND DATA RETENTION
Parameter
Min.
Unit
Minimum endurance
100,000
Data changes per bit
Data retention
100
Years
Test Circuit #1
Test Circuit #2
Circuit #3 SPICE Macro Model
VH/RH
VH/RH
Test Point
VS
Test Point
VW/RW
VL/RL
RTOTAL
RH
CH
VW/RW
VW
Force
Current
VLL/RL
CL
CW
RL
10pF
25pF
10pF
RW
A.C. CONDITIONS OF TEST
Input pulse levels
0V to 3V
Input rise and fall times
10ns
Input reference levels
1.5V
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X9315
A.C. OPERATING CHARACTERISTICS (Over recommended operating conditions unless otherwise specified)
Limits
Symbol
Parameter
Typ.(6)
Min.
Max.
Unit
tCl
CS to INC setup
100
ns
tlD
INC HIGH to U/D change
100
ns
tDI
U/D to INC setup
2.9
µs
tlL
INC LOW period
1
µs
tlH
INC HIGH period
1
µs
tlC
INC Inactive to CS inactive
1
µs
tCPH
CS Deselect time (NO STORE)
100
ns
tCPH
CS Deselect time (STORE)
10
ms
tIW
tCYC
tR, tF(7)
tPU(7)
tR VCC(7)
tWR
INC to Vw change
1
INC cycle time
5
µs
4
µs
INC input rise and fall time
Power up to wiper stable
VCC power-up rate
0.2
Store cycle
5
500
µs
5
µs
50
V/ms
10
ms
POWER UP AND DOWN REQUIREMENTS
There are no restrictions on the power-up or power-down conditions of VCC and the voltages applied to the
potentiometer pins provided that VCC is always more positive than or equal to VH, VL, and VW, i.e., VCC ≥ VH, VL,
VW. The VCC ramp rate spec is always in effect.
A.C. TIMING
CS
tCYC
tCI
tIL
tIH
(Store)
tCPH
tIC
90% 90%
10%
INC
tID
tF
DI
tR
U/D
tIW
VW
MI
(8)
Notes: (6) Typical values are for TA = 25°C and nominal supply voltage.
(7) This parameter is not 100% tested.
(8) MI in the A.C. timing diagram refers to the minimum incremental change in the VW output due to a change in the wiper position.
REV 1.3.2 1/14/03
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X9315
PERFORMANCE CHARACTERISTICS (TYPICAL)
Typical Noise
0
-10
-20
-30
Noise (dB)
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
0
10
20
30
40
50
60
70
80
90
100
110 120
130 140
150 160
170 180
85
105
190 200
Frequency (kHz)
Typical Rtotal vs. Temperature
10000
9800
9600
Rtotal
9400
9200
9000
8800
8600
8400
8200
8000
-55
-45
-35
-25
-15
-5
5
15
25
35
45
55
65
75
95
115 125 C°
Temperature
Typical Total Resistance Temperature Coefficient
0
-50
-100
-150
PPM
-200
-250
-300
-350
-55
-45
-35
-25
-15
-5
5
15
25
35
45
55
65
75
85
95
105
115
125
°C
Temperature
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X9315
Typical Wiper Resistance
800
700
Rw (Ohms)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
VCC = 2.7V
Tap
Typical Absolute% Error per Tap Position
40.0%
Absolute% Error
30.0%
20.0%
10.0%
0.0%
-10.0%
-20.0%
-30.0%
-40.0%
0
3
6
9
12
15
18
21
18
21
24
27
30
Tap
Typical Relative% Error per Tap Position
20.0%
Relative% Error
15.0%
10.0%
5.0%
0.0%
-5.0%
-10.0%
-15.0%
-20.0%
0
3
6
9
12
15
24
27
30
Tap
REV 1.3.2 1/14/03
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X9315
APPLICATIONS INFORMATION
Electronic digitally controlled (XDCP) potentiometers provide three powerful application advantages; (1) the
variability and reliability of a solid-state potentiometer, (2) the flexibility of computer-based digital controls, and (3)
the retentivity of nonvolatile memory used for the storage of multiple potentiometer settings or data.
Basic Configurations of Electronic Potentiometers
VR
VR
VH
VW/RW
VL
I
Three terminal potentiometer;
variable voltage divider
Two terminal variable resistor;
variable current
Basic Circuits
Buffered Reference Voltage
Noninverting Amplifier
Cascading Techniques
R1
+V
+5V
+V
+V
VS
+5V
VREF
VW
VOUT
–
VO
–
OP-07
+
LM308A
+
–5V
X
RW/VW
R2
+V
–5V
R1
RW/VW
VOUT = VW/RW
(a)
(b)
Voltage Regulator
VIN
VO = (1+R2/R1)VS
Comparator with Hysteresis
VO (REG)
317
VS
LT311A
R1
–
+
VO
Iadj
}
VO (REG) = 1.25V (1+R2/R1)+Iadj R2
}
R2
R1
R2
VUL = {R1/(R1+R2)} VO(max)
VLL = {R1/(R1+R2)} VO(min)
(for additional circuits see AN115)
REV 1.3.2 1/14/03
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X9315
PACKAGING INFORMATION
8-Lead Miniature Small Outline Gull Wing Package Type M
0.118 ± 0.002
(3.00 ± 0.05)
0.012 + 0.006 / -0.002
(0.30 + 0.15 / -0.05)
0.0256 (0.65) Typ.
R 0.014 (0.36)
0.118 ± 0.002
(3.00 ± 0.05)
0.030 (0.76)
0.0216 (0.55)
0.036 (0.91)
0.032 (0.81)
0.040 ± 0.002
(1.02 ± 0.05)
7° Typ.
0.008 (0.20)
0.004 (0.10)
0.0256" Typical
0.007 (0.18)
0.005 (0.13)
0.025"
Typical
0.150 (3.81)
Ref.
0.193 (4.90)
Ref.
0.220"
FOOTPRINT
0.020"
Typical
8 Places
NOTE:
1. ALL DIMENSIONS IN INCHES AND (MILLIMETERS)
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X9315
PACKAGING INFORMATION
8-Lead Plastic Dual In-Line Package Type P
0.430 (10.92)
0.360 (9.14)
0.260 (6.60)
0.240 (6.10)
Pin 1 Index
Pin 1
0.300
(7.62) Ref.
Half Shoulder Width On
All End Pins Optional
0.145 (3.68)
0.128 (3.25)
Seating
Plane
0.025 (0.64)
0.015 (0.38)
0.065 (1.65)
0.045 (1.14)
0.150 (3.81)
0.125 (3.18)
0.110 (2.79)
0.090 (2.29)
.073 (1.84)
Max.
0.060 (1.52)
0.020 (0.51)
0.020 (0.51)
0.016 (0.41)
0.325 (8.25)
0.300 (7.62)
0°
15°
Typ. 0.010 (0.25)
NOTE:
1. ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
2. PACKAGE DIMENSIONS EXCLUDE MOLDING FLASH
REV 1.3.2 1/14/03
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X9315
PACKAGING INFORMATION
8-Lead Plastic Small Outline Gull Wing Package Type S
0.150 (3.80) 0.228 (5.80)
0.158 (4.00) 0.244 (6.20)
Pin 1 Index
Pin 1
0.014 (0.35)
0.019 (0.49)
0.188 (4.78)
0.197 (5.00)
(4X) 7°
0.053 (1.35)
0.069 (1.75)
0.004 (0.19)
0.010 (0.25)
0.050 (1.27)
0.010 (0.25)
X 45°
0.020 (0.50)
0.050"Typical
0.050"
Typical
0° - 8°
0.0075 (0.19)
0.010 (0.25)
0.250"
0.016 (0.410)
0.037 (0.937)
0.030"
Typical
8 Places
FOOTPRINT
NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
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X9315
ORDERING INFORMATION
X9315X
X
X
X
VCC Limits
Blank = 5V ±10%
–2.7 = 2.7V to 5.5V
Temperature Range
Blank = Commercial = 0°C to +70°C
I = Industrial = –40°C to +85°C
Package
M = 8-Lead MSOP
P = 8-Lead Plastic DIP
S = 8-Lead SOIC
End to End Resistance
W = 10KΩ
U = 50KΩ
T = 100K
REV 1.3.2 1/14/03
P/N
MSOP Part Mark
X9315TM
AEJ
X9315TM-2.7
AEI
X9315TMI
ADZ
X9315TMI-2.7
ADY
X9315UM
AEL
X9315UM-2.7
AEK
X9315UMI
AEB
X9315UMI-2.7
AEA
X9315WM
AAW
X9315WM-2.7
AAU
X9315WMI
AAX
X9315WMI-2.7
AAV
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Characteristics subject to change without notice.
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