Datasheet
SLUS589B− NOVEMBER 2003 − REVISED FEBRUARY 2005
18
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APPLICATION INFORMATION
Layout Considerations
Successful operation of the TPS4000x controllers is dependent upon proper converter layout and grounding
techniques. High current returns for the SR MOSFET’s source, and ground connection of the input and output
capacitors, should be kept on a single ground plane. Bypassing capacitors at the device should return closely
to the GND (pin 5) of the device. The GND (pin 5) and PowerPAD should connect together at the device and
return to the main ground plane.
Proper operation of the Predictive Gate Drive circuits is dependent upon detecting low-voltage thresholds on
the SW node. To ensure that the signal at the SW pin accurately represents the voltage at the main switching
node, the connection from SW (pin 8) to the main switching node of the converter should be kept as short and
as wide as possible. If the SW trace should traverse multiple board layers between the device and the
MOSFETs, multiple vias should be used.
Gate drive outputs, LDRV and HDRV, should be kept as short as possible to minimize inductances of the traces.
While the controller does not require the usage of external resistors between the driver pins and the gates of
the MOSFETs, adding small resistors in series with very high gate charge MOSFETs could minimize the effects
of high frequency ringing.
The PowerPAD package provides low thermal impedance for heat removal from the device. The PowerPAD
derives its name and low thermal impedance from the large bonding pad on the bottom of the device. The circuit
board must have an area of solder-tinned-copper underneath the package. The dimensions of this area depend
on the size of the PowerPAD package (See Thermal Pad Mechanical Data on page 21)