I
NTEGRATED
C
IRCUITS
D
IVISION
CPC7232
R02 www.ixysic.com 9
2. Functional Description
The CPC7232 takes a serial stream of input data
along with a synchronous clock signal. As the clock
transits from low to high, the data at the input of each
shift register is shifted through from SR(n) to SR(n+1).
A high data bit, a "1," represents an ON switch; a low
data bit, a "0," represents an OFF switch. Data is input
and shifted through the internal shift register until all
eight shift register positions, SR0 through SR7, are in
the desired state.
D
IN
: The data-in line presents data bits to the
CPC7232 to be shifted through the internal shift
register.
CLK: The clock signal's rising edge is associated only
with shifting data into and through the shift register.
CL: The clear line overrides all other inputs. When CL
is high, the shift register is cleared to all 0s and all
latches are set low, which causes all output switches
to be turned OFF immediately. When CL is low, all
output switches remain in whatever state they are in,
ON or OFF, in response to CLK, latch inputs, and the
LE signal.
LE
: latch enable controls the state of the latches and
thus the state of the eight switches. If LE is high, then
the latches do not change states, but retain their most
recent status: either ON or OFF. With LE high, input
data and CLK have no effect on the state of the output
switches. If LE is low, then all latch outputs and their
switch states follow the inputs from the shift register.
LE is overridden by CL: no matter what state LE is in,
CL clears the latches. See “Truth Table” on page 10.
D
OUT
: The data-out pin is the output of SR7. After
eight clock pulses, the first bit of eight input data bits is
shifted to SR7 and appears on D
OUT
.
SW0 - SW7: The CPC7232 provides eight
high-voltage SPST output switches with a typical
on-resistance of 20. The two connections of each
switch are not polarity-sensitive.
V
PP
and V
NN
: Voltage inputs to the level shifters for
each switch channel that translate the voltage level of
the latch output signals to an appropriate level for the
voltages being switched.
The high-voltage output switches are turned on and off
in response to the data sent into the latches from the
shift register: data 0 turns a switch OFF, data 1 turns a
switch ON.
Two or more CPC7232 devices can be cascaded to
form an n-switch arrangement. The D
OUT
pin of the
first is connected to the D
IN
pin of the next in the
series. All devices are connected to the same clock
(CLK) signal. LE of all devices would normally be
connected, as would CL, but this is not necessary.
The first data bit applied to D
IN
of the CPC7232,
whether it's a single device or several cascaded
devices, ripples through to the last switch output in line
after the application of a full clocking sequence of 8
clock pulses per CPC7232. Setting the serial I/O
device to output the most significant bit (MSB) first,
results in the MSB appearing on SW7 of the last
device in line after a full clocking sequence.
CL
D
IN
CLK
LE
SW0
SW7
SW0
SW7
SW0
SW7
D
OUT
LE
CL
D
IN
CLK
D
OUT
LE
CL
D
IN
CLK
D
OUT
LE
CL
D
IN
CLK
CPC7232
CPC7232
CPC7232
