On-chip voltage regulator (VREG)

AN2871

8/25

Doc ID 15304 Rev 3

2.1.3

Recommended transistors

Transistor specifications give the minimum and maximum gain. The worst case is usually

significantly lower than the nominal figure on the transistor datasheet cover page. Moreover,

the datasheet values are usually given at room temperature.

The required gain should be calculated at cold temperature, because a bipolar transistor

has minimum gain at low temperature. The worst case gain at cold temperature can be

obtained from the transistor manufacturer or can be estimated using the graphs given in the

transistor datasheet.

The Table 1 lists the recommended ballast transistors.

In the following, as example, are shown parameters of BCP68 and BC817 transistors.

BCP68 NPN bipolar 1 A/1.5 W SOT223

This transistor is available from several semiconductor makers.

Table 1.

Approved NPN ballast transistor

Part

Manufacturer

1.

For automotive applications please check with the appropriate transistor vendor for automotive grade

certification

BCP68

ON Semi

BCP68

NXP

BCP68-25

Infineon

BCP68-25

BCX68

Infineon

BCX68-10;BCX68-16;BCX68-25

BC868

NXP

BC868

BC817

Infineon

BC817-16;BC817-25;BC817SU;

NXP

BC817-16;BC817-25

BCP56

ST

BCP56-16

Infineon

BCP56-10;BCP56-16

ON Semi

BCP56-10

NXP

BCP56-10;BCP56-16

Table 2.

ON Semiconductor datasheet: BCP68 electrical characteristics at 25 °C

Symbol

Parameter

Min

Typ

Max

Unit

—

DC current gain

50

85

60

—

—

—

—

375

—

—