PIP202-12M-2 Datasheet, PDF (11/20 Pages) NXP Semiconductors – DC-to-DC converter powertrain

Philips Semiconductors
PIP202-12M-2
DC-to-DC converter powertrain
9397 750 11943
Product data
output stage supply voltage
10 Ω
1 µF
control circuit
100
supply (12 V)
nF
VDDC CB VDDO
input voltage
from PWM controller
VO
VI
VSSC VSSO
Lout
Cin
output
Cout
signal ground
power ground
03ae27
Fig 12. External connection of power and signal lines.
To protect the control circuit from the transient voltages, the following precautions
must be taken. Refer to Figure 12.
1. The output stage ground (V_SSO) must be connected to the decoupling capacitor
(C_in) before joining the ground plane. Otherwise, the switching noise on V_SSO will
couple into the control circuit ground (V_SSC).
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.
3. It is essential that the V_SSC (signal ground) connection at the device is not
connected in the current return path between the V_SSO (power ground)
connection at the device and the V_DDO input capacitor.
4. It is also essential that the input to the V_DDC (logic power) filter is not connected in
the current path between the V_DDO (conversion power) connection at the device.
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
and PAD3 (Figure 2). PAD1 is connected to V_DDO, PAD2 is connected to V_SSC and
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
Rev. 02 — 24 November 2003
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
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