Philips Semiconductors

PIP202-12M-2

DC-to-DC converter powertrain

Product data

Rev. 02 — 24 November 2003

10 of 20

9397 750 11943

© Koninklijke Philips Electronics N.V. 2003. All rights reserved.

At 500 KHz and 20 A output current, the maximum dissipation in each PIP202-12M is

typically 4.5 W. The typical thermal resistance from junction to ambient is given in

Table 4. With thermal vias and forced air cooling, the thermal resistance of each

PIP202-12M from junction to ambient is 15 K/W. Assuming an ambient temperature

of 55

°C, the junction temperature (T

(1)

The thermal resistance between the junction and the printed-circuit board is 5 K/W.

(2)

11.2 Advantages of an integrated driver

One problem in the design of low-voltage, high-current DC-to-DC converters using

discrete components, is stray inductance between the various circuit elements.

Stray inductance in the gate drive circuit increases the switching times of the

MOSFETs and causes high-frequency oscillation of the gate voltage.

losses and electromagnetic interference. In discrete designs, high-frequency electric

and magnetic fields radiate from PCB tracks and couple into adjacent circuits.

By integrating the power MOSFETs and their drive circuits into a single package,

stray inductance is virtually eliminated, resulting in a compact, efficient design.

In discrete designs, the delays in the MOSFET drivers must be long enough to

ensure no cross-conduction even when using the slowest MOSFETs. Use of an

integrated driver allows the propagation delays in the MOSFET drivers to be precisely

matched to the MOSFETs. This minimizes switching losses and eliminates

cross-conduction whilst allowing the circuit to operate at a higher frequency.

11.3 External connection of power and signal lines

A major benefit of the PIP202-12M module is the ability to switch the internal power

MOSFETs faster than a DC-to-DC converter built from discrete components. This not

only reduces switching losses and increases system efficiency but also results in

the high rate of change of current (dI/dt) through the combined parasitic inductance of

the PCB tracks and the decoupling capacitors.

To minimize the amplitude of these transients, decoupling capacitors must be placed

chip ceramic capacitors are recommended.

T

j

P

tot

R

th j

a

–

()

×

T

amb

+

4.5

15

55

+

×

122.5

°C

==

=

T

pcb max

()

T

j max

()

P

tot

R

th j

pcb

–

()

×

–

122.5

4.5

5

×

–

100

°C

==

=