Technical Note

5/8

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2011.02 - Rev.B

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BD1603NUV

4.

Efficiency

The efficiency can be obtained from the following formula:

[]

%

100

×

I

×

V

Io

×

V

=

η

IN

IN

OUT

: Load current

: Input current

5.

Power consumption

The power consumption can be obtained from the following formula:

(You must set Io[mA] that it doesn't exceed Pd of this LSI.)

Because the allowable loss greatly depends on the PCB layout, the PCB layout must be designed considering heat dissipation.

In this PCB layout, the land pattern at the rear of this LSI must be directly connected to the ground plane.

6.

Output short-circuit current

When the output is short-circuited to the ground, outflow current is limited for LSI protection.

Once short-circuit is cleared, normal LSI operation is resumed (automatic return).

7.

Thermal shutdown

When the chip setting temperature is 185ºC (typ) or more, the thermal shutdown function is activated to turn off the

charge pump circuit.

When this temperature falls below to the thermal detection temperature, normal LSI operation is resumed. Accordingly,

the following ON and OFF operations are repeated as thermal operations unless the primary cause is resolved.

Fig.13 Thermal Detection Loop

8.

Setting the LED current

The LED current is set as follows.

The constant must be determined, considering variations in resistance and LED.



A

R

V

VOUT

ILED

F





R

: LED current setting resistance

Fig.14 Setting the LED Current

Temperature

Thermal detection

Circuit OFF

Temperature drop

Circuit ON

BD1603NUV

R