CAT5409
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3
PIN DESCRIPTIONS
Table 1. PIN DESCRIPTIONS
Pin#
(TSSOP)
Pin#
(SOIC)
Name Function
19 1 V
CC
Supply Voltage
20 2 R
L0
Low Reference Terminal
for Potentiometer 0
21 3 R
H0
High Reference Terminal
for Potentiometer 0
22 4 R
W0
Wiper Terminal for
Potentiometer 0
23 5 A2 Device Address
24 6 WP Write Protection
1 7 SDA Serial Data Input/Output
2 8 A1 Device Address
3 9 R
L1
Low Reference Terminal
for Potentiometer 1
4 10 R
H1
High Reference Terminal
for Potentiometer 1
5 11 R
W1
Wiper Terminal for
Potentiometer 1
6 12 GND Ground
7 13 NC No Connect
8 14 R
W2
Wiper Terminal for
Potentiometer 2
9 15 R
H2
High Reference Terminal
for Potentiometer 2
10 16 R
L2
Low Reference Terminal
for Potentiometer 2
11 17 SCL Bus Serial Clock
12 18 A3 Device Address
13 19 NC No Connect
14 20 A0 Device Address, LSB
15 21 R
W3
Wiper Terminal for
Potentiometer 3
16 22 R
H3
High Reference Terminal
for Potentiometer 3
17 23 R
L3
Low Reference Terminal
for Potentiometer 3
18 24 NC No Connect
SCL: Serial Clock
The CAT5409 serial clock input pin is used to clock all
data transfers into or out of the device.
SDA: Serial Data
The CAT5409 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-Ored with the other open
drain or open collector outputs.
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 CAT5409.
R
H
, R
L
: Resistor End Points
The four sets of R
H
and R
L
pins are equivalent to the
terminal connections on a mechanical potentiometer.
R
W
: Wiper
The four R
W
pins are equivalent to the wiper terminal of
a mechanical potentiometer.
WP
: Write Protect Input
The WP
pin when tied low prevents non-volatile writes to
the data registers (change of wiper control register is
allowed) and when tied high or left floating normal
read/write operations are allowed. See Write Protection on
page 8 for more details.
DEVICE OPERATION
The CAT5409 is four resistor arrays integrated with I
2
C
serial interface logic, four 6-bit wiper control registers and
sixteen 6-bit, non-volatile memory data registers. Each
resistor array contains 63 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
). R
H
and R
L
are symmetrical and
may be interchanged. 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 registers or the non-volatile memory data registers
via the I
2
C bus. Additional instructions allows data to be
transferred between the wiper control registers and each
respective potentiometer’s non-volatile data registers. Also,
the device can be instructed to operate in an “increment/
decrement” mode.
