CAT5270
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2
Pin Description
SCL: Serial Clock
The CAT5270 serial clock input pin is used to clock all
data transfers into or out of the device.
SDA: Serial Data
The CAT5270 bidirectional serial data pin is used to
transfer data into and out of the device. The SDA pin is an
open drain output and can be wire−OR’d with the other open
drain or open collector I/Os.
A0, A1, A2, A3: Device Address Inputs
These inputs set the device address when addressing
multiple devices. A total of sixteen devices can be addressed
on a single bus. A match in the slave address must be made
with the address input in order to initiate communication
with the CAT5270.
R
H
, R
L
: Resistor End Points
The two sets of R
H
and R
L
pins are equivalent to the
terminal connections on a mechanical potentiometer.
R
W
: Wiper
The R
W
pins are equivalent to the wiper terminal of a
mechanical potentiometer.
Table 1. PIN DESCRIPTION
Pin #
TSSOP−14
Name Function
1 A0 Device Address, LSB
2 V
CC
Supply Voltage
3 R
L0
Low Reference Terminal for
Potentiometer 0
4 R
H0
High Reference Terminal for
Potentiometer 0
5 R
W0
Wiper Terminal for Potentiometer 0
6 A2 Device Address
7 SDA Serial Data Input/Output
8 A1 Device Address
9 R
L1
Low Reference Terminal for
Potentiometer 1
10 R
H1
High Reference Terminal for
Potentiometer 1
11 R
W1
Wiper Terminal for Potentiometer 1
12 GND Ground
13 SCL Bus Serial Clock
14 A3 Device Address
Device Operation
The CAT5270 is two resistor arrays integrated with an I
2
C
compatible interface and two 8−bit wiper control registers.
Each resistor array contains 255 separate resistive elements
connected in series. The physical ends of each array are
equivalent to the fixed terminals of a mechanical
potentiometer (R
H
and R
L
). The tap positions between and
at the ends of the series resistors are connected to the output
wiper terminals (R
W
) by a CMOS transistor switch. Only
one tap point for each potentiometer is connected to its wiper
terminal at a time and is determined by the value of the wiper
control register. Data can be read or written to the wiper
control register via the I
2
C compatible interface. Also, the
device can be instructed to operate in an “increment/
decrement” mode.
