A
PPLICATION
N
OTE
A V A I L A B L E
AN104
Low Noise, Low Power, 32 Taps
X9315
E
2
POT
TM
Nonvolatile Digital Potentiometer
FEATURES
• Low Power CMOS
—V
CC
= 2.7V to 5.5V, Single Supply
—Active Current, 50
µ
A (Increment) max
—Active Current, 400
µ
A (Store) Max
—Standby Current, 1
µ
A Max
• Low Noise
• 31 Resistive Elements
—Temperature Compensated
—
±
20% End to End Resistance Range
—V
SS
to V
CC
Range
• 32 Wiper Tap Points
—Wiper Positioned via Three-Wire Interface
—Similar to TTL Up/Down Counter
—Wiper Position Stored in Nonvolatile Memory
and Recalled on Power-Up
• 100 Year Wiper Position Data Retention
• X9315Z = 1K
Ω
• X9315W = 10K
Ω
• Packages
—8-Lead SOIC
—8-Lead MSOP
—8-Pin DIP
FUNCTIONAL DIAGRAM
U/D
INC
CS
5-BIT
UP/DO
WN
COUNTER
CMOS SWITCH
VH
DESCRIPTION
The Xicor X9315 is a solid state "micropower" nonvol-
atile potentiometer and is ideal for digitally controlled
resistance trimming.
The X9315 is a resistor array composed of 31 resistive
elements. Between each element and at either end are
tap points accessible to the wiper element. The posi-
tion 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 sub-
sequent power-up operation.
The resolution of the X9315 is equal to the maximum
resistance value divided by 31. As an example, for the
X9315W (10K
Ω
) each tap point represents 323
Ω
.
All Xicor nonvolatile digital potentiometers are de-
signed and tested for applications requiring extended
endurance and data retention.
5-BIT
NONVOLA
TILE
MEMOR
Y
ONE
OF
THIRTY
-
TWO
WIPER
POSITION
DECODER
RESISTOR
ARRAY
STORE AND
RECALL
CONTR
OL
CIRCUITR
Y
VL
VW
6732 FM1
E
2
POT™ is a trademark of Xicor, Inc.
6732-2.0 5/30/97 T1/C0/D0 SH
1
Characteristics subject to change without notice
X9315
PIN DESCRIPTIONS
V
H
and V
L
The high (V
H
) and low (V
L
) terminals of the X9315 are
equivalent to the fixed terminals of a mechanical potenti-
ometer. The minimum voltage is V
SS
and the maximum is
V
CC
. It should be noted that the terminology of V
L
and V
H
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.
V
W
V
w
is the wiper terminal, 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
400
Ω
.
Up/Down (U/D)
The U/D input controls the direction of the wiper move-
ment and whether the counter is incremented or decre-
mented.
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.
DIP/SOIC/MSOP
INC
U/D
V
H
V
SS
1
2
3
4
X9315
8
7
6
5
V
CC
CS
V
L
V
W
PIN CONFIGURATION
6732 FM2
PIN NAMES
Symbol
V
H
V
W
V
L
V
SS
V
CC
U/D
INC
CS
Description
High Terminal
Wiper Terminal
Low Terminal
Ground
Supply Voltage
Up/Down Input
Increment Input
Chip Select Input
6732 FM T01
2
X9315
DEVICE 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 trans-
fers the potential at that point to the wiper.
The INC, U/D and CS inputs control the movement of the
wiper along the resistor array. With CS set LOW the
X9315 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 seven bit counter. The output of this counter
is decoded to select one of thirty two wiper positions
along the resistive array.
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 value of the counter is stored in nonvolatile memory
whenever CS transistions HIGH while the INC input is
also HIGH.
When the X9315 is powered-down, the last counter posi-
tion stored will be maintained in the nonvolatile memory.
When power is restored, the contents of the memory are
recalled and the counter is reset to the value last stored.
Operation Notes
The system may select the X9315, move the wiper and
deselect the device without having to store the latest
wiper position in nonvolatile memory. The wiper move-
ment is performed as described above; once the new
position is reached, the system would the keep INC LOW
while taking CS HIGH. The new wiper position would be
maintained until changed by the system or until a power-
up/down cycle recalled the previously stored data.
This would allow the system to always power-up to a pre-
set value stored in nonvolatile memory; then during sys-
tem operation minor adjustments could be made. The
adjustments might be based on user preference, system
parameter changes due to temperature drift, etc...
The state of U/D may be changed while CS remains
LOW. This allows the host system to enable the X9315
and then move the wiper up and down until the proper
trim is attained.
SYMBOL TABLE
WAVEFORM
INPUTS
Must be
steady
May change
from Low to
High
May change
from High to
Low
Don’t Care:
Changes
Allowed
N/A
OUTPUTS
Will be
steady
Will change
from Low to
High
Will change
from High to
Low
Changing:
State Not
Known
Center Line
is High
Impedance
6732 FM 3
3
X9315
ABSOLUTE MAXIMUM RATINGS*
Temperature under Bias .........................–65
°
C to +135
°
C
Storage Temperature..............................–65
°
C to +150
°
C
Voltage on CS, INC, U/D V
H
, V
L
and V
CC
with Respect to V
SS
.................................. –1V to +7V
∆
V = |V
H
–V
L
| ................................................................. 5V
Lead Temperature (Soldering 10 seconds)............. 300
°
C
Wiper Current ...........................................................
±
1mA
ANALOG CHARACTERISTICS
Electrical Characteristics
Temperature under Bias.........................–65
°
C to +135
°
C
End-to-End Resistance Tolerance ..........................
±
20%
Power Rating at 25
°
C ..............................................10mW
Wiper Current .................................................
±
1mA Max.
Typical Wiper Resistance ............................ 400
Ω
at 1mA
Typical Noise.................................. < –140dB
√
Hz Ref: 1V
Resolution
Resistance ................................................................... 3%
Linearity
Absolute Linearity
(1)
...........................................
±
1.0 Ml
(2)
Relative Linearity
(3)
...........................................
±
0.2 Ml
(2)
Temperature Coefficient
(–40
°
C to +85
°
C) ..............................+300 ppm/
°
C Typical
Ratiometric Temperature Coefficient ..................
±
20 ppm
Wiper Adjustability
Unlimited Wiper Adjustment (Non-Store operation)
Wiper Position Store Operations .......................... 100,000
Physical Characteristics
Marking Includes
Manufacturer’s Trademark
Resistance Value or Code
Date Code
*COMMENT
Stresses above those listed under “Absolute Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and 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.
Test Circuit #1
Test Circuit #2
V
H
TEST POINT
TEST POINT
V
W
V
L
6732 FM 4
V
H
VW
V
L
FORCE
CURRENT
6732 FM 5
Notes:
(1) Absolute Linearity is utilized to determine actual wiper voltage versus expected voltage
= (V
w(n)
(actual) – V
w(n)
(expected)) =
±
1 Ml Maximum.
(2) 1 Ml = Minimum Increment = R
TOT
/31.
(3) Relative Linearity is a measure of the error in step size between taps = V
W(n+1)
– [V
w(n)
+ Ml] = +0.2 Ml.
4
X9315
RECOMMENDED OPERATING CONDITIONS
Temperature
Commercial
Industrial
Min.
0
°
C
–40
°
C
Max.
+70
°
C
+85
°
C
6732 PGM T02
Supply Voltage
X9315
X9315-2.7
Limits
5V
±10%
2.7V to 5.5V
6732 PGM T03
D.C. OPERATING CHARACTERISTICS
(Over recommended operating conditions unless otherwise specified.)
Limits
Symbol
I
CC1
I
CC2
I
SB
I
LI
V
IH
V
IL
R
W
V
VH
V
VL
C
IN(5)
Parameter
V
CC
Active Current
(Increment)
V
CC
Active Current
(Store)
Standby Supply Current
CS, INC, U/D Input
Leakage Current
CS, INC, U/D Input
HIGH Voltage
CS, INC, U/D Input
LOW Voltage
Wiper Resistence
VH Terminal Voltage
VL Terminal Voltage
CS, INC, U/D Input
Capacitance
Min.
Typ.
(4)
Max.
50
400
1
±10
Units
µA
µA
µA
µA
V
Test Conditions
CS = V
IL
, U/D = V
IL
or V
IH
and
INC = 0.4V/2.4V @ max. t
CYC
CS = V
IH
, U/D = V
IL
or V
IH
and INC = V
IH
CS = V
CC
– 0.3V, U/D and
INC = V
SS
or V
CC
– 0.3V
V
IN
= V
SS
to V
CC
2
V
CC
+ 1
0.8
–0.5
V
Ω
V
V
pF
V
CC
= 5V, V
IN
= V
SS
,
T
A
= 25°C, f = 1MHz
6732 PGM T04
400
V
SS
V
SS
1000
V
CC
V
CC
10
Max. Wiper Current
±1mA
STANDARD PARTS
Part Number
X9315Z
X9315W
Maximum Resistance
1KΩ
10KΩ
Wiper Increments
32.3Ω
323Ω
Minimum Resistance
100Ω
100Ω
6732 PGM T05
Notes:
(4) Typical values are for T
A
= 25°C and nominal supply voltage.
(5) This parameter is periodically sampled and not 100% tested.
5
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