Philips Semiconductors

PIP202-12M-2

DC-to-DC converter powertrain

Product data

Rev. 02 — 24 November 2003

11 of 20

9397 750 11943

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

To protect the control circuit from the transient voltages, the following precautions

must be taken. Refer to Figure 12.

2. The control circuit supply must be filtered using a resistor-capacitor (RC) filter.

The values shown in Figure 12 are suitable for most applications.

11.4 Switching frequency

A high operating frequency reduces the size and number of capacitors needed to

filter the output current, and also reduces the size of the output inductors. The

disadvantage, however is higher dissipation due to switching and MOSFET driver

losses. For example, doubling the operating frequency of the circuit in Figure 11 from

500 kHz to 1 MHz would increase the power dissipation in each PIP202-12M from

4 W to 6 W, at an output current of 20 A in each PIP202-12M.

The maximum switching frequency is limited by thermal considerations, the

dissipation in the PIP202-12M device(s) and the thermal resistance from junction to

ambient.

11.5 Thermal design

The PIP202-12M has three pads on its underside. These are designated PAD1, PAD2

PAD3 is connected to VO. In addition to providing low inductance electrical

connections, these pads conduct heat away efficiently from the MOSFETs and

control IC to the printed-circuit board. The thermal resistance from junction to

printed-circuit board is approximately 5 K/W. In order to take full advantage of the low

Fig 12. External connection of power and signal lines.

VI

VDDC

VSSC

VO

VDDO

control circuit

supply (12 V)

output stage supply voltage

VSSO

CB

03ae27

output

100

nF

Lout

Cout

10

Ω

1

µF

Cin

signal ground

power ground

input voltage

from PWM controller