A
PPLICATION
N
OTE
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
• 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 V
CC
• Low power CMOS
—V
CC
= 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
• R
TOTAL
values = 10K
Ω
, 50K
Ω
, 100K
Ω
• Packages
—8-lead SOIC, MSOP and DIP
DESCRIPTION
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
R
H
/V
H
Control
and
Memory
R
W
/V
W
5-Bit
Nonvolatile
Memory
5-Bit
Up/Down
Counter
R
H
/V
H
V
CC
(Supply Voltage)
31
30
29
28
One
of
Thirty
Two
Decoder
2
Up/Down
(U/D)
Increment
(INC)
Device Select
(CS)
Transfer
Gates
Resistor
Array
R
L
/V
L
Store and
Recall
Control
Circuitry
V
SS
(Ground)
General
V
CC
V
SS
1
0
R
L
/V
L
R
W
/V
W
Detailed
XDCP
™
is a trademark of Xicor, Inc.
REV 1.3.2 1/14/03
www.xicor.com
Characteristics subject to change without notice.
1 of 13
X9315
PIN DESCRIPTIONS
R
H
/V
H
and R
L
/V
L
The high (R
H
/V
H
) and low (R
L
/V
L
) terminals of the
X9315 are equivalent to the fixed terminals of a
mechanical potentiometer. The minimum voltage is
V
SS
and the maximum is V
CC
. The terminology of R
L
/
V
L
and R
H
/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.
R
W
/V
W
R
W
/V
w
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 200
Ω
at V
CC
= 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
U/D
R
H
/V
H
V
SS
1
2
3
4
X9315
8
7
6
5
V
CC
CS
R
L
/V
L
R
W
/V
W
PIN NAMES
Symbol
R
H
/V
H
R
W
/V
W
R
L
/V
L
V
SS
V
CC
U/D
INC
CS
Description
High terminal
Wiper terminal
Low terminal
Ground
Supply voltage
Up/Down control input
Increment control input
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 t
IW
(INC to
V
W
change). The R
TOTAL
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.
REV 1.3.2 1/14/03
www.xicor.com
Characteristics subject to change without notice.
2 of 13
X9315
INSTRUCTIONS AND PROGRAMMING
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.
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...
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.
MODE SELECTION
CS
L
L
H
H
X
L
INC
U/D
H
L
X
X
X
Wiper Up
Mode
Wiper Down
Store Wiper Position
Standby Current
No Store, Return to Standby
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
REV 1.3.2 1/14/03
www.xicor.com
Characteristics subject to change without notice.
3 of 13
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
I
W
(10 seconds) .............................................. ±7.5mA
COMMENT
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
Commercial
Industrial
Min.
0°C
–40°C
Max.
+70°C
+85°C
Supply Voltage (V
CC
)
X9315
X9315-2.7
Limits
5V ±10%
2.7V to 5.5V
POTENTIOMETER CHARACTERISTICS
(Over recommended operating conditions unless otherwise stated.)
Limits
Symbol
V
VH
V
VL
R
W
R
W
I
W
Parameter
End to end resistance tolerance
V
H
terminal voltage
V
L
terminal voltage
Power rating
Wiper resistance
Wiper resistance
Wiper current
Noise
Resolution
Absolute linearity
(1)
Relative linearity
(2)
R
TOTAL
temperature coefficient
Ratiometric temperature coefficient
Min.
0
0
Typ.
Max.
±20
V
CC
V
CC
10
Unit
%
V
V
mW
Ω
Ω
mA
dBV
%
Test Conditions/Notes
R
TOTAL
≥
10 K
Ω
I
W
= 1mA, V
CC
= 5V
I
W
= 1mA, V
CC
= 2.7V
Ref: 1kHz
V
w(n)(actual)
–V
w(n)(expected)
V
w(n+1)
–[V
w(n)+MI
]
200
400
-120
3
400
1000
±3.75
±1
±0.2
±300
±20
10/10/25
MI
(3)
MI
(3)
ppm/°C
ppm/°C
pF
C
H
/C
L
/C
W
Potentiometer capacitances
See circuit #3
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) Relative linearity is a measure of the error in step size between taps = R
W(n+1)
—[R
w(n)
+ Ml] = ±0.2 Ml.
(3) 1 Ml = Minimum Increment = R
TOT
/31.
(4) Typical values are for T
A
= 25°C and nominal supply voltage.
(5) This parameter is periodically sampled and not 100% tested
REV 1.3.2 1/14/03
www.xicor.com
Characteristics subject to change without notice.
4 of 13
X9315
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
C
IN(5)
Parameter
V
CC
active current (Increment)
V
CC
active current (Store) (EE-
PROM 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
CS, INC, U/D input capacitance
Min.
Typ.
(4)
Max.
50
400
1
±10
Unit
µA
µA
µA
µA
V
V
pF
Test Conditions
CS = V
IL
, U/D = V
IL
or V
IH
and
INC = 0.4V @ max. t
CYC
CS = V
IH
, U/D = V
IL
or V
IH
and
INC = V
IH
@ max. t
WR
CS = V
CC
– 0.3V, U/D and
INC = V
SS
or V
CC
– 0.3V
V
IN
= V
SS
to V
CC
V
CC
x 0.7
–0.5
V
CC
+ 0.5
V
CC
x 0.1
10
V
CC
= 5V, V
IN
= V
SS
,
T
A
= 25°C, f = 1MHz
ENDURANCE AND DATA RETENTION
Parameter
Minimum endurance
Data retention
Min.
100,000
100
Unit
Data changes per bit
Years
Test Circuit #1
V
H
/R
H
Test Circuit #2
V
H
/R
H
Test Point
Circuit #3 SPICE Macro Model
R
TOTAL
R
H
C
H
C
W
25pF
10pF
R
W
C
L
10pF
R
L
V
S
Test Point
V
W
/R
W
V
L
/R
L
V
W
VW/R
W
Force
Current
V
L
/R
L
L
A.C. CONDITIONS OF TEST
Input pulse levels
Input rise and fall times
Input reference levels
0V to 3V
10ns
1.5V
REV 1.3.2 1/14/03
www.xicor.com
Characteristics subject to change without notice.
5 of 13
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