Datasheet

Minimizing I
CC
When I/Os Control LEDs
LED
Pn
V
CC
100 kW
V
CC
LED
3.3 V
5 V
Pn
V
CC
PCA9536
www.ti.com ....................................................................................................................................................... SCPS125F – APRIL 2006 – REVISED AUGUST 2008
When the I/Os are used to control LEDs, they are normally 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 supply
current, I
CC
, increases as V
IN
becomes lower than V
CC
and is specified as Δ I
CC
in Electrical Characteristics.
Designs needing to 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 Lower Voltage
Copyright © 2006 – 2008, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Link(s): PCA9536