ISL54302 Datasheet, PDF (7/16 Pages) Intersil Corporation – 12V, 1.5OHM Quad SPST Switch with Latched Parallel Interface

ISL54302
Test Circuits and Waveforms (Continued)
SX-CTRL SHOULD REMAIN IN DESIRED STATE, BEFORE DURING AND AFTER CS-LATCH.
CS-LATCH
INPUT
50%
50%
SX-CTRL
t_SETUP
100%
DATA = 1
t_HOLD
100%
DATA = 0
FIGURE 5. SETUP AND HOLD TIMES
ISL54302 Detailed Description
The ISL54302 quad analog switches offer switching capability
from a split-supply -3V and +9V or single 0V and 5V to 12V
supply. Please review “Power Supply Considerations” on
page 7 before powering up the device.
The user can employ multi-device control data in two ways.
The S1-S4-CTRL lines can be connected to several devices,
with each device having its own CS-LATCH connection to
the system controller. The other way is to have separate
S1-4-CTRL connections for each switch and a single
CS-LATCH connection to all ISL54302s.
Power Supply Considerations
The ISL54302 construction consists of CMOS analog
switches and four supply pins: VPLUS, VSS, VLOGIC, VDD
and GND. VPLUS and VSS determine the switch voltage
range of the four SPST CMOS switches and set their analog
voltage limits. There are no connections between the switch
contact signal path and GND.
VLOGIC and GND power the digital input/output logic level
shifters (thus setting the digital switching point). The level
shifters convert the external logic levels to VDD and VSS
signals to drive the internal digital circuitry.
VDD and VSS power the internal logic of the device. VDD
must always be held at a fixed 3V above VSS to avoid
device damage.
Whether operating split or single device, GND will
always be @ 0V and VLOGIC will always be @ 3V.
VDD should always remain 3V above VSS. VSS to
VPLUS should not exceed a maximum spread of more
than 12V. For examples, see the following:
SPLIT POSITIVE AND NEGATIVE SWITCH RANGE
OPERATION
• VSS = -3V, VDD = +0V, VPLUS = +9V, VLOGIC = 3V
• VSS = -1V, VDD = +2V, VPLUS = +11V, VLOGIC = 3V
POSITIVE SWITCH RANGE OPERATION
• VSS = 0V, VDD = +3V, VPLUS = +12V, VLOGIC = 3V
ISL54302 Parallel Communications
The ISL54302 operates based on parallel data. CTRL and
LATCH inputs are 3V level compatible. Setup and Hold times
relative to the rising the edge of the CS-LATCH input must
be maintained for proper operation. Switch control data is
clocked into internal registers on the rising edge of
CS-LATCH.
MULTIPLE DEVICE CONNECTION
The user can configure the four SX-CTRL inputs to connect
to several ISL54302’s. In this configuration each ISL54302
requires a separate/dedicated CS-LATCH input. Therefore,
each device will update at different times.
So in essence, the S1-S4-CTRL signals are multiplexed and
connected to all switch control inputs in parallel (see Figure 8).
For non-multiplexed connections, each SX-CTRL input must
have a dedicated logic input for each switch/each device. If
three ISL54302s are being used, the user must supply 12
dedicated SX-CTRL signals. All switches are then tied to the
same CS-LATCH pin and all devices would change state at
the same time.
ISL54302 CS-LATCH Pin Discussion
The ISL54302’s operational state does not change while
SX-CTRL inputs are changing. The user must insure that the
CS-LATCH pin remains low and does not change state while
SX-CTRL inputs are changing.
Once the user has set the SX-CTRL inputs, the CS-LATCH
pin is then utilized. Just as the CS-LATCH pin must remain
low during SX-CTRL setup, the SX-CTRL pins must remain
stable during and after the CS-LATCH operation.
The switch from present to next operation occurs on the
rising edge on the CS-LATCH pin. This rising edge transfers
data to the internal 4-bit switch control registers. This
transfer updates opening/closing of the four switches.
ISL54302 Power On Reset (POR)
Switch conditions are controlled during POR (Power On
Reset). During and after a POR condition, the switches are
opened until closed by the controller.
7
March 19, 2008