A
PPLICATION
N
OTE
A V A I L A B L E
AN42 • AN44–48 • AN50 • AN52 • AN53 • AN71 • AN92
Terminal Voltage ±5V, 100 Taps, Log Taper
X9C303
Digitally Controlled Potentiometer (XDCP
™
)
FEATURES
• Solid-state potentiometer
• Three-wire serial interface
• 100 wiper tap points
—Wiper position stored in nonvolatile memory
and recalled on power-up
• 99 resistive elements, log taper
—Temperature compensated
—End to end resistance, ±15%
—Terminal voltages, ±5V
• Low power CMOS
—V
CC
= 5V
—Active current, 3mA max.
—Standby current, 750µA max.
• High reliability
—Endurance, 100,000 data changes per bit
—Register data retention, 100 years
• X9C303, 32 k
Ω
• Packages
—8-lead TSSOP
—8-lead SOIC
—8-pin DIP
DESCRIPTION
The Xicor X9C303 is a digitally controlled potentiome-
ter (XDCP). The device consists of a resistor array,
wiper switches, a control section, and nonvolatile
memory. The wiper position is controlled by a three-
wire interface.
The resistor array is composed of 99 resistive ele-
ments. Between each element and at either end are
tap points accessible to the wiper terminal. 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 subsequent power-up operation.
The device can be used as a three-terminal potentio-
meter or as a two-terminal variable resistor in a wide
variety of applications ranging from control, to signal
processing, to parameter adjustment. Digitally-
controlled potentiometers provide three powerful appli-
cation advantages; (1) the variability and reliability of a
solid-state potentiometer, (2) the flexibility of com-
puter-based digital controls, and (3) the use of nonvol-
atile memory for potentiometer settings retention.
BLOCK DIAGRAM
U/D
INC
CS
7-Bit
Up/Down
Counter
99
98
97
7-Bit
Nonvolatile
Memory
96
One
of
One-
Hundred
Decoder
2
Store and
Recall
Control
Circuitry
1
0
R
L/
V
L
R
W/
V
W
XDCP
™
is a trademark of Xicor, Inc.
REV 1.1 4/27/01
R
H/
V
H
Transfer
Gates
Resistor
Array
V
CC
V
SS
www.xicor.com
Characteristics subject to change without notice.
1 of 10
X9C303
PIN DESCRIPTIONS
V
H
and V
L
The high (V
H
) and low (V
L
) terminals of the device are
equivalent to the fixed terminals of a mechanical
potentiometer. The minimum voltage is –5V and the
maximum is +5V. It should be noted that the terminol-
ogy 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 ter-
minal 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
40
Ω
.
Up/Down (U/D)
The U/D input controls the direction of the wiper move-
ment and whether the counter is incriminated 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 device
will be placed in the low power standby mode until the
device is selected once again.
PIN CONFIGURATION
DIP/SOIC/(TSSOP)
(CS) INC
(V
CC
) U/D
(INC) V
H
(U/D) V
SS
1
2
3
4
X9C303
8
7
6
5
V
CC
(V
L
)
CS (V
W
)
V
L
(V
SS
)
V
W
(V
H
)
V
L
R1 + R2 + . . . + Ri
VW
G i = 20Log ------------------------------------------------ = ---------
(
V L = 0V
)
-
R TOTAL
VS
R 1 + R 2 + . . . + R 99 @ 33KΩ = R TOTAL
(Refer Test Circuit 1)
PIN NAMES
Symbol
V
H
V
W
V
L
V
SS
V
CC
U/D
INC
CS
NC
Description
High Terminal (Potentiometer)
Wiper Terminal (Potentiometer)
Low Terminal (Potentiometer)
Ground
Supply Voltage
Up/Down Control Input
Increment Control Input
Chip Select Control Input
No Connection
POTENTIOMETER RELATIONSHIPS
S100
V
H
(V
S
)
S99
S98
V
W
R99
R98
S3
R2
R1
S2
S1
REV 1.1 4/27/01
www.xicor.com
Characteristics subject to change without notice.
2 of 10
X9C303
PRINCIPLES OF OPERATION
There are three sections of the X9C303: the input con-
trol, counter and decode section; the nonvolatile mem-
ory; 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 99 individual resistors connected in series. At either
end of the array and between each resistor is an elec-
tronic switch that transfers the potential 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 tem-
porarily be reduced by a significant amount if the wiper
is moved several positions.
When the device is powered-down, the last counter
position 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.
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 seven-bit counter. The output of this
counter is decoded to select one of one-hundred wiper
positions along the resistive array.
The value of the counter is stored in nonvolatile mem-
ory whenever CS transitions HIGH while the INC input
is also HIGH.
The system may select the X9C303, move the wiper,
and deselect the device without having to store the lat-
est wiper position in nonvolatile memory. The wiper
movement 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 posi-
tion would be maintained until changed by the system
or until a power-down/up cycle recalled the previously
stored data.
This would allow 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 1.1 4/27/01
www.xicor.com
Characteristics subject to change without notice.
3 of 10
X9C303
ABSOLUTE MAXIMUM RATINGS
Temperature under bias ....................–65°C to +135°C
Storage temperature .........................–65°C to +150°C
Voltage on CS, INC, U/D and V
CC
with respect to V
SS
.................................. –1V to +7V
Voltage on V
H
and V
L
referenced to V
SS
................................... –8V to +8V
∆
V = |V
H
–V
L
| X9C303 .......................................... 10V
Lead temperature (soldering, 10 seconds)...... +300°C
Wiper current ..................................................... ±1mA
COMMENT
Stresses above those listed under “Absolute Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only; 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 reli-
ability.
ANALOG CHARACTERISTICS
Electrical Characteristics
End-to-end resistance tolerance ....................... ±15%
Power rating at 25°C X9C303 ........................... 10mW
Wiper current ............................................ ±1mA Max.
Typical Electrical Taper
100.0%
90.0%
80.0%
70.0%
% Total Resistance
60.0%
50.0%
40.0%
30.0%
20.0%
10.0%
0.0%
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
R(V
H
–V
W
)
R(V
W
–V
L
)
99
4 of 10
Typical wiper resistance ...........................40
Ω
at 1mA
Typical resistor
noise ........................ 23 nV (RMS)/÷Hz at 1kHzPHZ
Typical charge pump noise.. 20 mV (RMS) @ 2.5 MHz
Relative Variation
Relative variation is a measure of the error in step size
between taps = log (V
w(n)
) – log (V
w(n-1)
) = 0.045 ± 0.003
for tap n = 2 – 99
Temperature Coefficient
(–40°C to +85°C) X9C303 .......... ±400 ppm/°C Typical
Ratiometric temperature coefficient ..............±20 ppm
Wiper Adjustability
Unlimited Wiper Adjustment (Non-Store operation)
Wiper Position Store
Operations ...................100,000 Data Changes per Bit
Physical Characteristics
Marking Includes
Manufacturer’s Trademark
Resistance Value or Code
Date Code
Tap
REV 1.1 4/27/01
www.xicor.com
Characteristics subject to change without notice.
X9C303
Test Circuit #1
V
H
Test Circuit #2
V
H
Test Point
Circuit #3SPICE Macro Model
R
TOTAL
R
H
C
H
C
W
25pF
R
W
C
L
10pF
R
L
V
S
Test Point
V
W
V
L
V
L
V
W
Force
Current
10pF
RECOMMENDED OPERATING CONDITIONS
Temperature
Commercial
Industrial
Military
Min.
0°C
–40°C
–55°C
Max.
+70°C
+85°C
+125°C
Supply Voltage
X9C303
Limits
5V ±10%
D.C. OPERATING CHARACTERISTICS
(Over recommended operating conditions unless otherwise specified.)
Limits
Symbol
I
CC
I
SB
I
LI
V
IH
V
IL
R
W
V
H
V
L
C
IN(2)
C
H
/C
L
/C
W
Parameter
V
CC
active current
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 resistance
V
H
terminal voltage
V
L
terminal voltage
CS, INC, U/D input capacitance
Potentiometer capacitance
Min.
Typ.
1
1
200
Max.
3
750
±10
Unit
mA
µA
µA
V
V
Ω
V
V
pF
pF
Test Conditions
CS = V
IL
, U/D = V
IL
or V
IH
and
INC = 0.4V to 2.4V @ max. t
CYC
CS = V
CC
– 0.3V, U/D and INC
= V
SS
or V
CC
– 0.3V
V
IN
= V
SS
to V
CC
2
–1
40
–5
–5
V
CC
+ 1
0.8
100
+5
+5
10
10/10/25
Max. Wiper Current ±1mA
V
CC
= 5V, V
IN
= V
SS
,
T
A
= 25°C, f = 1MHz
See Circuit 3
Standard Parts
Part Number
X9C303
Maximum Resistance
32KΩ
Wiper Increments
Log Taper
Minimum Resistance
40Ω Typical
Notes:
(1) Typical values are for T
A
= 25°C and nominal supply voltage.
(2) This parameter is periodically sampled and not 100% tested.
REV 1.1 4/27/01
www.xicor.com
Characteristics subject to change without notice.
5 of 10
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