Datasheet

AGND
PH
VOUT
PGND
VIN/PVIN
C
IN2
R
SET
R
RT
C
OUT1
SENSE+
Via
SENSE+
Via
C
OUT3
C
IN1
C
SS
C
OUT2
AGND to PGND
connection
SENSE+
Via
SENSE+
Via
AGND
Plane
PGND
Plane
Vias to
Topside
PGND
Copper
Vias to
Topside
AGND
Copper
LMZ31503
SNVS992 –JULY 2013 www.ti.com
Thermal Shutdown
The internal thermal shutdown circuitry forces the device to stop switching if the junction temperature exceeds
175°C typically. The device reinitiates the power up sequence when the junction temperature drops below 165°C
typically.
Layout Considerations
To achieve optimal electrical and thermal performance, an optimized PCB layout is required. Figure 43 and
Figure 44 show two layers of a typical PCB layout. Some considerations for an optimized layout are:
• Use large copper areas for power planes (VIN, VOUT, and PGND) to minimize conduction loss and thermal
stress.
• Place ceramic input and output capacitors close to the module pins to minimize high frequency noise.
• Locate additional output capacitors between the ceramic capacitor and the load.
• Place a dedicated AGND copper area beneath the LMZ31503.
• Isolate the PH copper area from the VOUT copper area using the AGND copper area.
• Connect the AGND and PGND copper area at one point; near the output capacitors.
• Place R
SET
, R
RT
, and C
SS
as close as possible to their respective pins.
• Use multiple vias to connect the power planes to internal layers.
Figure 43. Typical Top-Layer Recommended Figure 44. Typical GND-Layer Recommended
Layout Layout
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