CAT4201_15 Datasheet, PDF (7/12 Pages) ON Semiconductor – High Efficiency Step Down LED Driver

CAT4201
Table 6. 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 1 mA and voltage
transients of up to 40 V can be applied. To ensure accurate
LED current regulation, the VBAT voltage should be 3 V
higher than the total forward voltage of the LED string. A
bypass capacitor of 4.7 mF or larger is recommended
between VBAT and GND.
CTRL is the analog dimming and control input. An internal
pull−down current of 20 mA allows the LEDs to shutdown
if CTRL is left floating. Voltages of up to 40 V can be safely
handled by the CTRL input pin.
When the CTRL voltage is less than 0.9 V (typ), the LEDs
will shutdown to zero current. When the CTRL voltage is
greater than about 2.6 V, full scale brightness is applied to the
LED output. At voltages of less than around 2.6 V, 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 40 V 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 1.2 V. 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. The RSET pin must not be left floating. The
highest recommended resistor value between RSET and
ground is 90 kW.
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