cat3604v Catalyst Semiconductor, cat3604v Datasheet - Page 10

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

V
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).
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.
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
4.3V may be used. Selecting LEDs with lower V
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
3.5V V
lower supply voltage of 0.2V.
Doc. No. MD-5029, Rev. B
IN
ON OFF
R
SET
1µF
C
IN
F
Figure 3. Application with 3 LEDs
LED, the driver will stay in 1x mode for a
VIN
EN
RSET
C1+
CAT3604V
1µF
C1-
GND
C2+
F
VOUT
1µF
LED1
LED2
LED3
LED4
LED is selected instead of a
C2-
F
) ranging from 1.3V to
F
C
1µF
OUT
is
10
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
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.
IN
and C
Figure 4. PCB Layout
OUT
can be implemented with the
Characteristics subject to change without notice
© Catalyst Semiconductor, Inc.