PIP202-12M Datasheet, PDF (10/20 Pages) NXP Semiconductors – DC to DC converter powertrain

Philips Semiconductors
PIP202-12M
DC to DC converter powertrain
At 500 KHz and 20 A output current, the maximum dissipation in each PIP202-12M is
5.7 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 is15 K/W. Assuming a maximum ambient temperature of
55 °C, the maximum junction temperature (T_j(max)) is given by:
T _j(max) = P_tot × R_{th( j – a)} + T _amb = 5.7 × 15 + 55 = 140.5°C
(1)
The thermal resistance between the junction and the printed-circuit board is 5 K/W.
Therefore, the maximum printed-circuit board temperature (T_pcb(max)) is given by:
T _pcb(max) = T _j(max) – P_tot × R_{th( j – pcb)} = 140.5 – 5.7 × 5 = 112°C
(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.
Stray inductance in the high-current loop between V_DDO and V_SSO causes switching
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 it also results in
higher transient voltages on the device supply lines (V_DDO and V_SSO). This is due to
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
between V_DDO and V_SSO, as close as possible to the device pins. Low inductance,
chip ceramic capacitors are recommended.
9397 750 10031
Product data
Rev. 01 — 15 July 2002
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
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