LTC3370_15 Datasheet, PDF (19/24 Pages) Linear Technology – 4-Channel 8A Configurable Buck DC/DCs

LTC3370
Applications Information
PCB Considerations
When laying out the printed circuit board, the following
list should be followed to ensure proper operation of the
LTC3370:
1. The exposed pad of the package (Pin 33) should connect
directly to a large ground plane to minimize thermal and
electrical impedance.
2. Each of the input supply pins should have a decoupling
capacitor.
3. The connections to the switching regulator input supply
pins and their respective decoupling capacitors should
be kept as short as possible. The GND side of these
capacitors should connect directly to the ground plane
of the part. These capacitors provide the AC current
to the internal power MOSFETs and their drivers. It is
important to minimize inductance from these capacitors
to the V_IN pins of the LTC3370.
4. The switching power traces connecting SWA, SWB,
SWC, SWD, SWE, SWF, SWG, and SWH to the induc-
tors should be minimized to reduce radiated EMI and
parasitic coupling. Due to the large voltage swing of
the switching nodes, high input impedance sensitive
nodes, such as the feedback nodes, should be kept far
away or shielded from the switching nodes or poor
performance could result.
5. The GND side of the switching regulator output capaci-
tors should connect directly to the thermal ground plane
of the part. Minimize the trace length from the output
capacitor to the inductor(s)/pin(s).
6. In a multiple power stage buck regulator application
the trace length of switch nodes to the inductor must
be kept equal to ensure proper operation.
7. Care should be taken to minimize capacitance on the
TEMP pin. If the TEMP voltage must drive more than
~30pF, then the pin should be isolated with a resistor
placed close to the pin of a value between 10k and 100k.
Keep in mind that any load on the isolation resistor will
create a proportional error.
For more information www.linear.com/LTC3370
3370f
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