A1

B1

C1

C2

C3

B3

A3

A2

LM3500

SNVS231G – AUGUST 2003 – REVISED MAY 2013

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DESCRIPTION (CONTINUED)

Two LM3500 options are available with different output voltage capabilities. The LM3500-21 has a maximum

output voltage of 21V and is typically suited for driving 4 or 5 white LEDs in series. The LM3500-16 has a

maximum output voltage of 16V and is typically suited for driving 3 or 4 white LEDs in series (maximum number

of series LEDs dependent on LED forward voltage). If the primary white LED network should be disconnected,

the LM3500 uses internal protection circuitry on the output to prevent a destructive over-voltage event.

A single external resistor is used to set the maximum LED current in LED-drive applications. The LED current

can easily be adjusted using a pulse width modulated (PWM) signal on the shutdown pin. In shutdown, the

LM3500 completely disconnects the input from output, creating total isolation and preventing any leakage

currents from trickling into the LEDs.

Connection Diagram

Figure 1. 8-bump DSBGA

PIN FUNCTIONS

Pin

Name

Function

A1

AGND

Analog ground.

B1

Analog and Power supply input.

C1

PMOS source connection for synchronous rectification.

C2

Switch pin. Drain connections of both NMOS and PMOS power devices.

C3

GND

Power Ground.

B3

FB

Output voltage feedback connection.

A3

NC

No internal connection made to this pin.

A2

SHDN

Shutdown control pin.

AGND(pin A1): Analog ground pin. The analog ground pin should tie directly to the GND pin.

to this pin to minimize EMI radiation.

GND(pin C3): Power ground pin. Tie directly to ground plane.

FB(pin B3): Output voltage feedback connection. Set the primary White LED network current with a resistor from

the FB pin to GND. Keep the current setting resistor close to the device and connected between the FB and

GND pins.

NC(pin A3): No internal connection is made to this pin. The maximum allowable voltage that can be applied to

this pin is 7.5V.

2

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