LM5032

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SNVS344B – MARCH 2005 – REVISED DECEMBER 2014

Figure 32 illustrates the switching nodes of the two interleaved phases, and the resulting output ripple at twice

the switching frequency. This was measured at Vin of 24 V, where duty cycle is approx. 50% and maximum

ripple-cancellation occurs.

Figure 31. Efficiency vs. Load and Vin

Figure 32. Output Ripple at 24-V Vin

9 Power Supply Recommendations

The VCC pin requires a local decoupling capacitor to ground for stability of the internal regulator from the VIN

pin. This decoupling capacitor also provides the current pulses to drive the gates of the external MOSFETs

through the driver output pins. The decoupling capacitor should be placed close to the VCC and GND1/GNS2

pins, and should be tracked directly to the pins.

The two ground pins (GND1 and GND2) must be connected together with a short direct connection.

10 Layout

10.1 Layout Guidelines

The LM5032 Current Sense and PWM comparators are very fast, and respond to short duration noise pulses.

The components at the CS, COMP, SS, DCL, UVLO, and the RT/SYNC pins should be as physically close as

possible to the IC, thereby minimizing noise pickup in the PC board tracks.

Layout considerations are critical for the current sense filter. If current sense transformers are used, both leads of

each transformer secondary should be routed to the sense filter components and to the IC pins. The ground side

of each transformer should be connected via a dedicated PC board track to its appropriate GND pin, rather than

through the ground plane.

If the current sense circuits employ sense resistors in the drive transistor sources, low inductance resistors

should be used. In this case, all the noise sensitive low current ground tracks should be connected in common

near the IC, and then a single connection made to the power ground (sense resistor ground point). The outputs

of the LM5032 should have short direct paths to the power MOSFETs in order to minimize inductance in the PC

board traces.

The two ground pins (GND1, GND2) must be connected together with a short direct connection to avoid jitter due

to relative ground bounce in the operation of the two regulators.

If the internal dissipation of the LM5032 produces high junction temperatures during normal operation, the use of

wide PC board traces can help conduct heat away from the IC. Judicious positioning of the PC board within the

end product, along with use of any available air flow (forced or natural convection) can help reduce the junction

temperatures.

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