Datasheet

Px
LED
100 kW
V
CC
V
CC
3.3 V
Px
LED
5 V
V
CC
V
CC
Ramp-Up Re-Ramp-Up
Time to Re-Ramp
Time
Ramp-Down
V
CC_RT
V
CC_RT
V
CC_FT
V
CC_TRR_GND
TCA6424
SCPS175A –NOVEMBER 2007–REVISED NOVEMBER 2009 www.ti.com
Minimizing I
CC
When I/Os Control LEDs
When the I/Os are used to control LEDs, normally they are connected to V
CC
through a resistor as shown in
Figure 14. The LED acts as a diode so, when the LED is off, the I/O V
IN
is about 1.2 V less than V
CC
. The ΔI
CC
parameter in Electrical Characteristics shows how I
CC
increases as V
IN
becomes lower than V
CC
. Designs that
must minimize current consumption, such as battery power applications, should consider maintaining the I/O pins
greater than or equal to V
CC
when the LED is off.
Figure 15 shows a high-value resistor in parallel with the LED. Figure 16 shows V
CC
less than the LED supply
voltage by at least 1.2 V. Both of these methods maintain the I/O V
IN
at or above V
CC
and prevent additional
supply current consumption when the LED is off.
Figure 15. High-Value Resistor in Parallel With the LED
Figure 16. Device Supplied by a Low Voltage
Power-On Reset Requirements
In the event of a glitch or data corruption, TCA6424 can be reset to its default conditions by using the power-on
reset feature. Power-on reset requires that the device go through a power cycle to be completely reset. This
reset also happens when the device is powered on for the first time in an application.
The two types of power-on reset are shown in Figure 17 and Figure 18.
Figure 17. V
CC
is Lowered Below 0.2 V or 0 V and Then Ramped Up to V
CC
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Product Folder Link(s): TCA6424