CAT3626 Datasheet, PDF (10/16 Pages) Catalyst Semiconductor – 6-Channel LED Driver with I2C Interface

Block Diagram
CAT3626
1 mF
C_1− C₁₊
1 mF
C_2− C₂₊
V_IN
C_IN
1 mF
1x mode (LDO)
1.5x Charge Pump
V_OUT
C_OUT
1 mF
EN
SDA
SCL
Serial
Interface
1 MHz
Oscillator
Reference
Voltage
Current
Setting DAC
Mode Control
Registers
LEDA1
LEDA2
LEDB1
LEDB2
LEDC1
LEDC2
6 Current
Sink Regulators
GND
Figure 25. 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 400 ms) 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:
• RegA stores the LED current for group A (LEDA1 and
LEDA2 channels),
• RegB stores the LED current for group B (LEDB1 and
LEDB2 channels),
• RegC stores the LED current for group C (LEDC1 and
LEDC2 channels),
• 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.
Table 6. REGISTER ADDRESS AND DATA CONFIGURATION (Note 3)
Register
Name
Register
Address
Bit 7 Bit 6
Bit 5
Bit Pattern
Bit 4
Bit 3
Bit 2
RegA
0
X
X
RegB
1
X
X
See Table 7 for values
RegC
2
X
X
RegEn
LEDC2
LEDC1
LEDB2
LEDB1
3
X
X
On = 1
On = 1
On = 1
On = 1
Off = 0
Off = 0
Off = 0
Off = 0
3. X = not used, 1 = logic high, 0 = logic low
Bit 1
LEDA2
On = 1
Off = 0
Bit 0
LEDA1
On = 1
Off = 0
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