LTC4449
10
4449fa
APPLICATIONS INFORMATION
Bypassing and Grounding
The LTC4449 requires proper bypassing on the V
LOGIC
, V
CC
and V
BOOST – TS
supplies due to its high speed switching
(nanoseconds) and large AC currents (amperes). Careless
component placement and PCB trace routing may cause
excessive ringing and under/overshoot.
To obtain the optimum performance from the LTC4449:
• Mount the bypass capacitors as close as possible
between the V
LOGIC
and GND pins, the V
CC
and GND
pins, and the BOOST and TS pins. The leads should
be shortened as much as possible to reduce lead
inductance.
• Use a low inductance, low impedance ground plane
to reduce any ground drop and stray capacitance.
Remember that the LTC4449 switches greater than
5A peak currents and any signifi cant ground drop will
degrade signal integrity.
• Plan the power/ground routing carefully. Know where
the large load switching current is coming from and
going to. Maintain separate ground return paths for
the input pin and the output power stage.
• Keep the copper trace between the driver output pin
and the load short and wide.
• Be sure to solder the Exposed Pad on the back side of
the LTC4449 packages to the board. Correctly soldered
to a double-sided copper board, the LTC4449 has a
thermal resistance of approximately 64°C/W. Failure
to make good thermal contact between the exposed
back side and the copper board will result in thermal
resistances far greater.
