Datasheet

PGND
Plane
R
SET
VOUT sense
Via
LOAD
VOUT sense
Via
Thermal
Vias
AGND
VOUTPGND
C
OUT1
VIN
PH
C
OUT2
C
IN1
AGND to PGND
Connection
LMZ35003
SNVS988 –JULY 2013 www.ti.com
Thermal Shutdown
The internal thermal shutdown circuitry forces the device to stop switching if the junction temperature exceeds
180°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 40 and
Figure 41 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 LMZ35003.
• Isolate the PH copper area from the VOUT copper area using the PGND copper area.
• Connect the AGND and PGND copper area at one point; at pins 8 & 9.
• 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.
• Use a dedicated sense line to connect R
SET
to VOUT near the load for best regulation.
Figure 40. Typical Top-Layer Recommended Figure 41. Typical PGND-Layer Recommended
Layout Layout
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