YDA138

10

●

Allowable Dissipation

The power dissipation of YDA138 is limited by the junction temperature rating (125℃) and package thermal resistance

(35.9℃/W).

The power dissipation and junction temperature of YDA138 can be found by the following formula.

For the use of YDA138, take care not to exceed the power dissipation and junction temperature.

・

Formula for the Power Dissipation

Ploss = (Pout * Rpn / Rl) * 2 + Idc * Vdc

Ploss

：

Allowable Dissipation (W)

Pout

：

Output Power (W)

Rpn

：

0.66 (Constant)

Rl

：

Load Resistor (Ω)

Idc

：

Vdc

：

Power supply voltage (V)

・

Formula for the junction temperature

Tj = Ploss * θja + Ta

Ploss

：

Allowable Dissipation (W)

θja

：

35.9 (Constant/ package thermal resistance (℃/W))

Ta

：

Ambient Temperature (℃)

●

Mounting

The package (42SSOP) for YDA138 has Thermal Pad for radiation on the bottom. This Thermal Pad does not need

soldering on the board.

・

Example of Pattern

Thermal resistance of the package is 35.9℃/W. This thermal resistance was measured under the following conditions:

mounting board 136mm×85mm, copper leaf board density 154%, no wind. In addition, a part of the board that faces to

Thermal Pad is a pattern (4mm*6mm) without etching resist, the pattern is connected to the opposite side by through-hole

(φ0.4).

最大許容損失 vs 周囲温度

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

1020

30

40

5060

7080

90

周囲温度　(℃)

YDA138 の最大許容損失

Maximum allowable dissipation vs ambient temperature

Ambient temperature (℃)

Maximum allowable dissipation of YDA138