CAT4201 Datasheet, PDF (7/15 Pages) Catalyst Semiconductor – 350mA High Efficiency Step Down LED Driver

CAT4201
PIN DESCRIPTION
Pin Name Function
1 CTRL Analog dimming control and shutdown pin.
2 GND Ground reference.
3 RSET RSET pin. A resistor connected between the pin and ground sets the average LED current.
4 SW Interface to the inductor.
5 VBAT Supply voltage for the device.
PIN FUNCTION
VBAT is the supply input to the device. Typical current
conduction into this pin is less than 1mA and voltage
transients of up to 40V can be applied. To ensure
accurate LED current regulation, the VBAT voltage
should be 3V higher than the total forward voltage of
the LED string. A bypass capacitor of 4.7µF or larger
is recommended between VBAT and GND.
CTRL is the analog dimming and control input. An
internal pull-down current of 20µA allows the LEDs to
shutdown if CTRL is left floating. Voltages of up to
40V can be safely handled by the CTRL input pin.
When the CTRL voltage is less than 0.9V (typ), the
LEDs will shutdown to zero current. When the CTRL
voltage is greater than about 2.6V, full scale
brightness is applied to the LED output. At voltages of
less than around 2.6V, the LED current is
progressively dimmed until shutdown.
For lamp replacement applications, or applications
where operation in dropout mode is expected, it is
recommended that the CTRL pin voltage be derived
from the LED cathode terminal.
GND is the ground reference pin. This pin should be
connected directly to the ground plane on the PCB.
SW pin is the drain terminal of the internal low
resistance high-voltage power MOSFET. The inductor
and the Schottky diode anode should be connected to
the SW pin. Voltages of up to 40V can be safely
handled on the SW pin. Traces going to the SW pin
should be as short as possible with minimum loop
area. The device can handle safely “open-LED” or
“shorted-LED” fault conditions.
RSET pin is regulated at 1.2V. A resistor connected
between the RSET pin and ground sets the LED full-
scale brightness current. The external resistance
value and the CTRL pin voltage determine the LED
current during analog dimming.
© Catalyst Semiconductor, Inc.
7
Characteristics subject to change without notice
Doc. No. MD-5025 Rev. D