cat3636 Catalyst Semiconductor, cat3636 Datasheet - Page 8

• Manufacturer Part Number: cat3636
• Description: 6-channel Quad-modetm Fractional Led Driver In Tqfn3x3
• Manufacturer: Catalyst Semiconductor

CAT3636
BLOCK DIAGRAM
BASIC OPERATION
At power-up, the CAT3636 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
LED currents, the device remains in 1x operating
mode.
If the input voltage is insufficient or falls to a level
wher e the regulated currents cannot be maintained,
the device automatically switches into 1.33x mode
(after a fixed delay time of about 400μs). In 1.33x
mode, the output voltage is approximately equal to
1.33 times the input supply voltage (less any internal
voltage losses).
If the input voltage is insufficient again or falls to a
level where the regulated currents cannot be
maintained, the device will automatically switch to the
1.5x boost mode (after a fixed delay time of about
400μs). In 1.5x mode, the output is approximately
equal to 1.5 times the input supply voltage (less any
internal voltage losses).
Doc. No. MD-5020 Rev. D
EN/SET
V
IN
100kΩ
Registers
Interface
Serial
C
Figure 2. CAT3636 Functional Block Diagram
1.33x, 1.5x, 2x Charge Pump
1-
Setting DAC
0.8, 1.1MHz
Oscillator
Referece
Voltage
Current
1x mode (LDO)
C
1+
C
2-
Mode Control
C
2+
8
If the input voltage fails more or is still insufficient to
drive the LEDs, it will automatically switch again into
2x mode where the output is approximately equal to 2
times the input supply voltage (less any internal
voltage losses).
If the device detects a sufficient input voltage is
present to drive all LED currents in 1x mode, it will
change automatically back to 1x mode. This only
applies for changing back to the 1x mode
GND
6 Current
Sink Regulators
V
LEDA1
LEDA2
LEDB1
LEDB2
LEDC1
LEDC2
OUT
Characteristics subject to change without notice
© Catalyst Semiconductor, Inc.