LED DRIVER PR4401/PR4402

Connection from Battery

Due to high peak currents, it is important to connect the PR4401/PR4402 to the battery

with short, low resistance wires, to achieve the best performance. A voltage drop along the

wire affects LED current, efficiency and minimum startup and operating voltage.

This is most critical for applications with low inductivity and high current.

In cases where a longer wire from the battery cannot be avoided, a capacitor should be

placed close to the Vcc and Gnd pin of PR4401. Typically capacitors between 220nF and

1µF are used.

With PR4402 operated at higher currents, a blocking capacitor is usually necessary even

if wires or board layout are optimized.

Using Different Battery Types

The input voltage must be 1.90V at maximum. At higher voltages the circuit may not

trigger and start up correctly. Therefore operation with one Alkaline, NiCd, or NiMH cell

(AA or AAA type) is recommended.

Alkaline button cells can also be used for supply. However, since high peak currents are

drawn from the battery, button cells are recommended only with inductors of 22µH or

more, depending on the battery type. A capacitor at the supply pins of PR4401 may also

improve performance with button cells.

Lithium batteries are not suitable due to their higher voltage.

Approximate battery lifetime:

Battery

Battery Lifetime, typical

L1= 22µH, LED mean current 12mA

Battery Lifetime, typical

L1= 10µH, LED mean current 23mA

AA (Mignon, LR 6/AM-3)

55 h

27 h

AAA (Micro, LR 03/AM-4)

22 h

8 h

Conditions: one white LED connected, measured with single 1.5V TDK Alkaline battery.

Battery lifetime depends on battery capacity and operating conditions. Therefore the times

indicated here can only give a rough indication of achievable times.

Connecting several LEDs in parallel

When several LEDs are connected in parallel, it is necessary to match the forward voltage

of these LEDs, to achieve a uniform brightness. The total current of all LEDs together

corresponds approximately to the mean output current for operation with one LED.

Vcc

Gnd

Vout

PR4401

Vbat =1.2V or 1.5V

L1=10µH

Matching

White

LEDs

© PREMA Semiconductor GmbH 2006-2008

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