2-Channel, 256-Position
Digital Potentiometer
a
AD5207
FEATURES
FUNCTIONAL BLOCK DIAGRAM
256-Position, 2-Channel
Potentiometer Replacement
10 kꢀ, 50 kꢀ, 100 kꢀ
A1
W1
B1
A2
W2
B2
Power Shut-Down, Less than 5 ꢁA
2.7 V to 5.5 V Single Supply
ꢂ2.7 V Dual Supply
3-Wire SPI-Compatible Serial Data Input
Midscale Preset During Power-On
SHDN
RDAC1 REGISTER
R
RDAC2 REGISTER
R
V
DD
V
SS
APPLICATIONS
LOGIC
POWER-
CS
ON
Mechanical Potentiometer Replacement
Stereo Channel Audio Level Control
Instrumentation: Gain, Offset Adjustment
Programmable Voltage-to-Current Conversion
Programmable Filters, Delays, Time Constants
Line Impedance Matching
RESET
8
AD5207
CLK
SDI
SDO
SERIAL INPUT REGISTER
DGND
Automotive Electronics Adjustment
The first two bits are address bits. The following eight bits are
the data bits that represent the 256 steps of the resistance value.
The reason for two address bits instead of one is to be compatible
with similar products such as AD8402 so that drop-in replacement
is possible. The address bit determines the corresponding VR
latch to be loaded with the data bits during the returned positive
edge of CS strobe. A serial data output pin at the opposite end
of the serial register allows simple daisy chaining in multiple
VR applications without additional external decoding logic.
GENERAL DESCRIPTION
The AD5207 provides dual channel, 256-position, digitally
controlled variable resistor (VR) devices that perform the same
electronic adjustment function as a potentiometer or variable
resistor. Each channel of the AD5207 contains a fixed resistor with
a wiper contact that taps the fixed resistor value at a point
determined by a digital code loaded into the SPI-compatible
serial-input register. The resistance between the wiper and either
end point of the fixed resistor varies linearly with respect to the
digital code transferred into the VR latch. The variable resistor
offers a completely programmable value of resistance, between
the A Terminal and the wiper or the B Terminal and the wiper.
The fixed A-to-B terminal resistance of 10 kΩ, 50 kΩ or 100 kΩ
has a 1% channel-to-channel matching tolerance with a nomi-
nal temperature coefficient of 500 ppm/°C. A unique switching
circuit minimizes the high glitch inherent in traditional switched
resistor designs and avoids any make-before-break or break-
before-make operation.
An internal reset block will force the wiper to the midscale posi-
tion during every power-up condition. The SHDN pin forces an
open circuit on the A Terminal and at the same time shorts the
wiper to the B Terminal, achieving a microwatt power shutdown
state. When SHDN is returned to logic high, the previous latch
settings put the wiper in the same resistance setting prior to
shutdown. The digital interface remains active during shutdown;
code changes can be made to produce new wiper positions when
the device is resumed from shutdown.
Each VR has its own VR latch, which holds its programmed
resistance value. These VR latches are updated from an internal
serial-to-parallel shift register, which is loaded from a standard
3-wire serial-input digital interface. Ten bits, to make up the
data word, are required and clocked into the serial input register.
The AD5207 is available in 1.1 mm thin TSSOP-14 package,
which is suitable for PCMCIA applications. All parts are guaran-
teed to operate over the extended industrial temperature range
of –40°C to +125°C.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
www.analog.com
© Analog Devices, Inc., 2001
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