Datasheet

UDG-09067
TPS51218
Thermal Pad
DRVL
4 5
VIN
1 mF
VFB
V5IN
6
V
OUT
2
TRIP
5
RF
0.1 mF
100 W
VTT_SENSE
VSS_SENSE
GND
TPS51218
SLUS935B – MAY 2009– REVISED FEBRUARY 2012 www.ti.com
from gate of the low-side MOSFET through the gate driver and GND pad of the device, and back to
source of the low-side MOSFET through ground. Connect negative node of V5IN capacitor, source of the
low-side MOSFET and GND pad of the device at ground as close as possible. (Refer to loop #3 of
Figure 19)
• Since the TPS51218 controls output voltage referring to voltage across V
OUT
capacitor, the top-side resistor of
the voltage divider should be connected to the positive node of V
OUT
capacitor. In a same manner both
bottom side resistor and GND pad of the device should be connected to the negative node of V
OUT
capacitor.
The trace from these resistors to the VFB pin should be short and thin. Place on the component side and
avoid via(s) between these resistors and the device.
• Connect the overcurrent setting resistors from TRIP pin to ground and make the connections as close as
possible to the device. The trace from TRIP pin to resistor and from resistor to ground should avoid coupling
to a high-voltage switching node.
• Connect the frequency setting resistor from RF pin to ground, or to the PGOOD pin, and make the
connections as close as possible to the device. The trace from the RF pin to the resistor and from the resistor
to ground should avoid coupling to a high-voltage switching node.
• Connections from gate drivers to the respective gate of the high-side or the low-side MOSFET should be as
short as possible to reduce stray inductance. Use 0.65 mm (25 mils) or wider trace and via(s) of at least
0.5 mm (20 mils) diameter along this trace.
• The PCB trace defined as switch node, which connects to source of high-side MOSFET, drain of low-side
MOSFET and high-voltage side of the inductor, should be as short and wide as possible.
LAYOUT CONSIDERATIONS TO REMOTE SENSING
Figure 20. Remote Sensing of Output Voltage Using the TPS51218
• Make a Kelvin connection to the load device.
• Run the feedback signals as a differential pair to the device. The distance of these parallel pair should be as
short as possible.
• Run the lines in a quiet layer. Isolate them from noisy signals by a voltage or ground plane.
18 Submit Documentation Feedback Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s): TPS51218