AATIAN78 Datasheet, PDF (2/4 Pages) SiGe Semiconductor, Inc. – Triple I/O Expander Load Switch with Serial Control

EV-101
AAT4291 RGB EVAL
Triple I/O Expander Load Switch with Serial Control
Getting Started
The evaluation board comes with a battery pack
attached. In this configuration, V_IN is supplied from
three standard “AAA” alkaline batteries. Under new
conditions for the batteries, the input voltage is gen-
erally 4.7V ~ 4.8V and falls off depending on the
degree of discharge and load conditions. If desired,
the batteries can be removed and an independent,
DC supply can be used.
There are five buttons on the board. Their functions
are as follows:
• SW1: Increments through the eight Output Set-
ting states (Table 2 in the product datasheet).
• SW2: Increments B_LED duty cycle.
• SW3: Increments G_LED duty cycle.
• SW4: Increments R_LED duty cycle.
• SW5: Brings EN/SET low (shuts down the
AAT4291 device).
Notes:
1. Buttons 1 through 4 will automatically incre-
ment if held down.
2. Buttons 2 through 4 are set up so that a user
can independently control the corresponding
R, G, or B LED brightness. This is done by
incrementing the PWM duty cycle through the
following states: 0%, 25%, 50%, 75%, 100%,
0%, …
The PIC microcontroller toggles the EN/SET line
high and low at 500kHz. The rise and fall times of
the EN/SET signal are small relative to the period,
so T_HI and T_LO are roughly 1µs (see Figure 1). T_HI
and T_LO depend on the µC's internal RC oscillator,
so the 1µs reference is an approximate figure and
subject to the precision of the RC oscillator.
Figure 2: Typical EN/SET Signal.
2
EV-101.2005.01.1.0