CAT3626 Datasheet, PDF (9/14 Pages) Catalyst Semiconductor – 6-Channel LED Driver with I2C Interface

BLOCK DIAGRAM
CAT3626
Figure 2. CAT3626 Functional Block Diagram
BASIC OPERATION
At power-up, the CAT3626 starts operating in 1x
mode where the output will be approximately equal to
the input supply voltage (less any internal voltage
losses). If the output voltage is sufficient to regulate all
LEDs currents the device remains in 1x operating
mode.
If the input voltage is insufficient or falls to a level
where the regulated currents cannot be maintained,
the device automatically switches (after a fixed time of
400µs) into 1.5x mode.
In 1.5x mode, the output is approximately equal to 1.5
times the input supply voltage (less any internal
voltage losses).
The above sequence is repeated each and every time
the chip is either powered-up or taken out of shutdown
(via EN pin), or the RegEn register is accessed by
write cycle.
LED CURRENT SETTING
The LED current setting is programmed via the I²C
serial interface and is stored in four
8-bit registers RegA, RegB, RegC and RegEn as
follows:
ƒ RegA stores the LED current for group A
(LEDA1 and LEDA2 channels),
ƒ RegB stores the LED current for group B
(LEDB1 and LEDB2 channels),
ƒ RegC stores the LED current for group C
(LEDC1 and LEDC2 channels),
ƒ RegEn selects the on/off state of each of the
6 LED channels.
At each write access to RegEn, the driver
automatically reconfigures to the mode (1x or 1.5x)
that provides the highest efficiency.
© 2006 Catalyst Semiconductor, Inc.
9
Characteristics subject to change without notice
Doc. No. 5014 Rev. A