CAV4201

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7

Table 6. PIN DESCRIPTION

Pin

Name

Function

1

CTRL

Enable and analog dimming control input 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 enable and analog dimming 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, the device is enabled and 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 k

W.