CAT5401
http://onsemi.com
3
PIN DESCRIPTIONS
Table 1. PIN DESCRIPTIONS
Pin#
(SOIC)
Pin#
(TSSOP)
Name Function
1 19 V
CC
Supply Voltage
2 20 R
L0
Low Reference Terminal
for Potentiometer 0
3 21 R
H0
High Reference Terminal
for Potentiometer 0
4 22 R
W0
Wiper Terminal for
Potentiometer 0
5 23 CS Chip Select
6 24 WP Write Protection
7 1 SI Serial Input
8 2 A1 Device Address
9 3 R
L1
Low Reference Terminal
for Potentiometer 1
10 4 R
H1
High Reference Terminal
for Potentiometer 1
11 5 R
W1
Wiper Terminal for
Potentiometer 1
12 6 GND Ground
13 7 NC No Connect
14 8 R
W2
Wiper Terminal for
Potentiometer 2
15 9 R
H2
High Reference Terminal
for Potentiometer 2
16 10 R
L2
Low Reference Terminal
for Potentiometer 2
17 11 SCK Bus Serial Clock
18 12 HOLD Hold
19 13 SO Serial Data Output
20 14 A0 Device Address, LSB
21 15 R
W3
Wiper Terminal for
Potentiometer 3
22 16 R
H3
High Reference Terminal
for Potentiometer 3
23 17 R
L3
Low Reference Terminal
for Potentiometer 3
24 18 NC No Connect
SI: Serial Input
SI is the serial data input pin. This pin is used to input all
opcodes, byte addresses and data to be written to the
CAT5401. Input data is latched on the rising edge of the
serial clock.
SO: Serial Output
SO is the serial data output pin. This pin is used to transfer
data out of the CAT5401. During a read cycle, data is shifted
out on the falling edge of the serial clock.
SCK: Serial Clock
SCK is the serial clock pin. This pin is used to synchronize
the communication between the microcontroller and the
CAT5401. Opcodes, byte addresses or data present on the SI
pin are latched on the rising edge of the SCK. Data on the SO
pin is updated on the falling edge of the SCK.
A0, A1: Device Address Inputs
These inputs set the device address when addressing
multiple devices. A total of four 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
CAT5401.
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.
CS
: Chip Select
CS
is the Chip select pin. CS low enables the CAT5401
and CS
high disables the CAT5401. CS high takes the SO
output pin to high impedance and forces the devices into a
Standby mode (unless an internal write operation is
underway). The CAT5401 draws ZERO current in the
Standby mode. A high to low transition on CS
is required
prior to any sequence being initiated. A low to high
transition on CS
after a valid write sequence is what initiates
an internal write cycle.
WP
: Write Protect
WP
is the Write Protect pin. The Write Protect pin will
allow normal read/write operations when held high. When
WP
is tied low, all non-volatile write operations to the Data
registers are inhibited (change of wiper control register is
allowed). WP
going low while CS is still low will interrupt
a write to the registers. If the internal write cycle has already
been initiated, WP
going low will have no effect on any write
operation.
HOLD
: Hold
The HOLD
pin is used to pause transmission to the
CAT5401 while in the middle of a serial sequence without
having to retransmit entire sequence at a later time. To pause,
HOLD
must be brought low while SCK is low. The SO pin
is in a high impedance state during the time the part is
paused, and transitions on the SI pins will be ignored. To
resume communication, HOLD
is brought high, while SCK
is low. (HOLD
should be held high any time this function is
not being used.) HOLD
may be tied high directly to V
CC
or
tied to V
CC
through a resistor.
