CAT3604V Datasheet, PDF (10/15 Pages) Catalyst Semiconductor – 4-Channel Quad-Mode™ LED Driver with Open/Short LED Detection

CAT3604V
Unused LED Channels
For applications not requiring all the channels, it is
recommended to connect the unused LED pins
directly to VOUT (see Figure 3).
1µF
1µF
V_IN
C_IN
1µF
ON OFF
R_SET
C1+
VIN
C1- C2+ C2-
VOUT
EN
RSET
CAT3604V
GND
LED1
LED2
LED3
LED4
C_OUT
1µF
Figure 3. Application with 3 LEDs
Protection Mode
If an LED is disconnected, the device senses that,
run the diagnostics, then ignores that channel and
goes back to the most effective mode. When all LEDs
are disconnected, the device runs diagnostics and
goes to 1x mode where the output is basically equal to
the input voltage.
External Components
The driver requires four external 1μF ceramic capa-
citors for decoupling input, output, and for the charge
pump. Both capacitors type X5R and X7R are
recommended for the LED driver application. In all
charge pump modes, the input current ripple is kept
very low by design and an input bypass capacitor of
1μF is sufficient.
In 1x mode, the device operates in linear mode and
does not introduce switching noise back onto the
supply.
Recommended Layout
In charge pump mode, the driver switches internally at
a high frequency. It is recommended to minimize trace
length to all four capacitors. A ground plane should
cover the area under the driver IC as well as the
bypass capacitors. Short connection to ground on
capacitors C_IN and C_OUT can be implemented with the
use of multiple via. A copper area matching the TQFN
exposed pad (TAB) must be connected to the ground
plane underneath. The use of multiple via improves
the package heat dissipation.
As soon as the output exceeds about 6V, the driver
resets itself and reevaluate the mode.
If the die temperature reaches +150°C, the device
enters a thermal protection shutdown mode. When the
device temperature drops to about +130°C, the device
resumes normal operation.
LED Selection
LEDs with forward voltages (V_F) ranging from 1.3V to
4.3V may be used. Selecting LEDs with lower V_F is
recommended in order to extend battery life and keep
the driver in 1x mode longer as the battery voltage
decreases.
For example, if a 3.3V V_F LED is selected instead of a
3.5V V_F LED, the driver will stay in 1x mode for a
lower supply voltage of 0.2V.
Figure 4. PCB Layout
Doc. No. MD-5029, Rev. B
10
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice