Low Noise, Low Power
X9015
Digitally-Controlled Potentiometer
FEATURES
•
•
•
•
•
•
•
32 Taps
Three-wire Up/Down Serial Interface
V
CC
= 2.7V & 5V
Operating I
CC
= 50µA Max.
Standby current = 1µA Max.
R
TOTAL
= 50K
Ω
Packages, SOIC-8
DESCRIPTION
The Xicor X9015 is a 32 tap potentiometer that is volatile.
The device consists of a string of 31 resistors that can be
programmed to connect the R
W
/V
W
wiper output with
any of the nodes between the connecting resistors. The
connection point of the wiper is determined by
information communicated to the device on the 3-wire
port. The 3-wire port changes the tap position by a falling
edge on the increment pin. Direction the wiper moves is
determined by the state of the Up/Down pin. The wiper
position at power up is tap #15.
The X9015 can be used in a wide variety of applications
that require a digitally controlled variable resistor to set
analog values.
FUNCTIONAL DIAGRAMS
V
CC
(Supply Voltage)
U/D
INC
CS
5-BIT
UP/DOWN
COUNTER
31
30
29
28
ONE
OF
THIRTY TWO
DECODER
R
H
/V
H
UP/DOWN
(U/D)
INCREMENT
(INC)
DEVICE SELECT
(CS)
CONTROL
R
H
/V
H
R
W
/V
W
TRANSFER
GATES
R
L
/V
L
2
V
SS
(Ground)
GENERAL
V
CC
V
SS
CONTR
OL
CIRCUITRY
1
0
RESISTOR
ARRAY
R
L
/V
L
R
W
/V
W
DETAILED
9900-2009.3 9/20/99 PS
1
Characteristics subject to change without notice
X9015
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
X9015 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. At power up the wiper
position is at tap #15 (V
L
/R
L
= tap #0).
Up/Down (U/D)
The U/D input controls the direction of the wiper
movement and whether the tap postion 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. When
CS is returned HIGH while the INC input is LOW the
X9015 will be placed in the low power standby mode until
the device is selected once again.
PIN CONFIGURATION
SOIC
INC
U/D
R
H
/V
H
V
SS
1
2
3
4
X9015
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
2
X9015
PRINCIPLES OF OPERATION
There are two sections of the X9015: the input control,
counter and decode section; 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 resis-
tor array to the wiper output. The resistor array is com-
prised of 31 individual resistors connected in series.
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 wiper position is
lost. When power is restored, the wiper is set to tap #15.
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 system may select the X9015, move the wiper and
deselect the device. The new wiper position will be
maintained until changed by the system or until a power-
up/down cycle.
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
X
L
INC
U/D
H
L
X
X
Wiper Up
Mode
Wiper Down
Standby Current
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
3
X9015
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
*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. Exposure to absolute maximum rating condi-
tions 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
)
X9015
X9015-2.7
Limits
5V ±10%
2.7V to 5.5V
POTENTIOMETER CHARACTERISTICS (Over recommended operating conditions unless otherwise stated.)
Limits
Symbol
R
TOTAL
V
VH
V
VL
Parameter
End to End Resistance Variation
V
H
Terminal Voltage
V
L
Terminal Voltage
Power Rating
Min.
–20
0
0
Typ.
Max.
+20
V
CC
V
CC
10
Units
%
V
V
mW
Ω
Ω
mA
dBV
%
Test Conditions/Notes
R
TOTAL
≤
50K
Ω
I
W
= 1mA, V
CC
= 5V
I
W
= 1mA, V
CC
= 2.7V
R
W
R
W
I
W
Wiper Resistance
Wiper Resistance
Wiper Current
Noise
Resolution
Absolute Linearity
(1)
Relative Linearity
(2)
R
TOTAL
Temperature Coefficient
Ratiometric Temperature Coefficient
Potentiometer Capacitances
-1
-0.2
200
400
400
1000
±1
-120
3
+1
+0.2
±300
±20
10/10/25
Ref: 1kHz
V
w(n)(actual)
– V
w(n)(expected)
V
w(n+1)
– [V
w(n)+MI
]
MI
(3)
MI
(3)
ppm/°C
ppm/°C
pF
C
H
/C
L
/C
W
Notes:
See circuit #3
(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 = V
W(n+1)
– [V
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.
4
X9015
D.C. OPERATING CHARACTERISTICS
(Over recommended operating conditions unless otherwise specified.)
Limits
Symbol
I
CC1
I
SB
I
LI
V
IH
V
IL
C
IN(5)
Parameter
V
CC
Active Current
(Increment)
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
1
±10
Units
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
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
Test Circuit #1
Test Circuit #2
V
H
/R
H
TEST POINT
Circuit #3 SPICE Macromodel
R
TOTAL
R
H
C
H
C
W
25pF
10pF
R
W
C
L
10pF
R
L
V
H
/R
H
V
S
TEST POINT
V
W
/R
W
V
L
/R
L
V
L
/R
L
L
V
W
VW/R
W
FORCE
CURRENT
5
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