LTC4446

9

4446f

APPLICATIONS INFORMATION

Unlike a pure capacitive load, a power MOSFET’s gate

voltage level during switching. A MOSFET’s capacitive load

power dissipation can be calculated using its gate charge,

on TG and BG:

To avoid damage due to power dissipation, the LTC4446

includes a temperature monitor that will pull BG and TG

low if the junction temperature rises above 160°C. Normal

operation will resume when the junction temperature cools

to less than 135°C.

Bypassing and Grounding

(nanoseconds) and large AC currents (Amperes). Careless

component placement and PCB trace routing may cause

excessive ringing.

To obtain the optimum performance from the LTC4446:

A. Mount the bypass capacitors as close as possible

TS pins. The leads should be shortened as much as

possible to reduce lead inductance.

B. Use a low inductance, low impedance ground plane

to reduce any ground drop and stray capacitance.

Remember that the LTC4446 switches greater than

3A peak currents and any significant ground drop will

degrade signal integrity.

C. 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.

D. Keep the copper trace between the driver output pin

and the load short and wide.

E. Be sure to solder the Exposed Pad on the back side of

the LTC4446 package to the board. Correctly soldered

LTC4446 has a thermal resistance of approximately

40°C/W for the MS8E package. Failure to make good

thermal contact between the exposed back side and

the copper board will result in thermal resistances far

greater than 40°C/W.