AAT4296/98
Five/Six Channel Push/Pull I/O Expander
These devices may also be used for load switching
applications, as well as I/O expansion. Since the
VCC is gated to each output through a slew rate lim-
ited low on-resistance switch, they are ideal for
controlling applications circuits with light load cur-
rent requirements. Such applications could include
simple LED function indicator lamps, RGB LED
fashion lighting, audio and RF circuits, or any other
system with a power requirement that does not
exceed the thermal dissipation limits of the load
switch and device package.
The state of each output is controlled via the
EN/SET pin using AnalogicTech's S2Cwire inter-
face. To enable a respective switch, a series of
clocked pulses should be applied to the EN/SET
pin. The number of pulses clocked will determine
the switch configuration based on the truth table
shown in Table 1. At the end of the serial pulse
data set, the EN/SET set pin should be held high
to then latch the clocked data and enable the
desired switch configuration. When the device is
enabled with the EN/SET held to a logic high state,
the device quiescent current consumption will typ-
ically increase to 3µA and normal ambient room
temperatures. If output sequencing of the switches
is not necessary, all of the outputs will be switched
on simultaneously on the first rising edge of the
EN/SET pin by simply pulling the EN/SET to a
logic high level. The default switch position for
one clock pulse is all switches "on." However, if
output sequencing is desired, a series of pulses on
the EN/SET pin will set the outputs to the desired
state (refer to Table 1 for output settings).
Each device push/pull output may be represented
by the following circuit and simplified equivalent
model (Figures 1 and 2):
VCC
Control
OUT
The AAT4296/98 offers two different options when
the switches are in the off state. For applications
with an active pull down or auto-discharge
requirement, the internal N-channel switch will
connect the output node to ground with a series
resistance of 2Ω.
Figure 1: Push/Pull Output Circuit.
S2Cwire Serial Interface
VCC
The ON/OFF state of the output is controlled by the
EN/SET serial data input. An internal control
counter is clocked on the rising edge of the
EN/SET pin and is decoded into the 32/64 possible
states (see Table 1).
3Ω
OUT
Control
2Ω
Figure 2: Simplified Equivalent Model.
10
4296.2006.12.1.3
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
