cat3604v Catalyst Semiconductor, cat3604v Datasheet - Page 9

• Manufacturer Part Number: cat3604v
• Description: 4-channel Quad-mode? Led Driver With Open/short Led Detection
• Manufacturer: Catalyst Semiconductor

BLOCK DIAGRAM
BASIC OPERATION
At power-up, the CAT3604V 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
where 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).
This sequence repeats in the 1.33x and 1.5x mode
until the driver enters the 2x mode. In 1.5x mode, the
output voltage is approximately equal to 1.5 times
the input supply voltage. While in 2x mode, the
output is approximately equal to 2 times the input
supply voltage.
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. The
difference between the input voltage when exiting 1x
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
V
IN
RSET
VIN
EN
Figure 2. CAT3604V Functional Block Diagram
C
1.33x, 1.5x, 2x Charge Pump
1-
Reference
Oscillator
1, 1.3MHz
Current
Voltage
Setting
1x mode (LDO)
C
1+
C
2-
Mode Control
C
9
2+
mode and returning to 1x mode is called the 1x mode
transition hysteresis (V
LED Current Selection
The LED current is set to by the external resistor RSET
as follows:
The EN pin enables and disables the device. The LED
driver enters a “zero current” shutdown mode if EN is
held low for 1.5ms or more.
As soon as the EN input goes low, all LED channels
are instantly disabled, where the LED current is set to
zero. As long as the CAT3604V is not in shutdown
mode, the LEDs turn on as soon as the EN goes high.
GND
LED current =
VOUT
LED Channel
Current Regulators
LED1
LED2
LED3
LED4
HYS
) and is about 500mV
132 ×
R
0
6 .
SET
V
Doc. No. MD-5029 Rev. B
CAT3604V