4 & 6 CHANNEL CHARGE PUMPS FOR WHITE LED BIAS

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FSP3302/FSP3303

TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)

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APPLICATION INFORMATION

CAPACITOR SELECTION

For best performance, use only ceramic capacitors, as they offer small size, low ESR, low cost, and high reliability.

Since the dropout resistance is dependent on the ESR of the capacitors, lower ESR also allows the circuit to supply

the required output currents at lower input voltage. X7R and X5R ceramic types are most stable (±15%) over bias

voltage and temperature ranges and thus are highly recommended. Lower cost Y5V and Z5U ceramic types vary

widely with voltage and temperature, and they should only be used after careful verification of the effects the

capacitance degradation has on the application.

Choose values for the flying capacitors of at least 1µF. For best results choose input and output capacitors of at least

1µF.

WHITE LED SELECTION

The FSP3302/FSP3303 are designed to bias multiple parallel white LEDs. The LED currents are internally matched

and change very little with each LED's forward voltage. For best operation, ensure that the maximum LED forward

voltage is 4.2V.

The FSP3302/FSP3303 utilizes a proprietary design that results in significantly better dropout performance than

competing products. Whereas other products maintain constant current for input voltages down to 3.0V, the

FSP3302/FSP3303 are capable of providing constant output current for input voltages extending down to as low as

2.7V.

EFFICIENCY

The FSP3302/FSP3303 automatically adjust their operating mode to ensure the highest possible efficiency for a

given set of operating conditions. The theoretical maximum efficiency of a charge pump is a function of its operating

mode. Compared to this theoretical maximum efficiency, the FSP3302/FSP3303 achieve efficiency that is within just

2% of the theoretical maximum for full scale output currents. This ensures the lowest possible battery current and

the maximum possible battery life in portable applications.