LTC4449

Question

I have a few questions related to the LTC4449 MOSFET driver. 
 
 Do you recommend any power supply sequencing for the Vlogic and Vcc inputs?
 
 I plan to provide 3.3V for Vlogic and 5.0V for Vcc. The attached MOSFET bridge will have a Vin of 12V.

Since the part does not have a dedicated enabled pin, is it ok to lower the Vlogic input to 0V to act as an output disable?
 
 I don't have the ability to tri-state the PWM input pin for this feature.

Do you recommend a low oh resistor in series with the bootstrap capacitor?
 
 I noticed that some other FET drivers recommend a series resistor to limit slew rate and to minimize the ringing at the switch node.

Thanks for your assistance - 
 Scott

Gene323 · Accepted Answer

Hi Scott, 
 Answer 1, I would recommend power sequencing as follows: 5V to VCC first, 3.3V to Vlogic second, and last 12V to Vin. Since you are providing 3.3V to Vlogic pin, the PWM signal to IN pin should have 3.3V amplitude signal. 
 Answer 2, You can lower the voltage at Vlogic pin to 0V to disable the outputs. 
 Answer 3, I would recommend putting 0 ohm shunt resistor as a place holder in series with the bootstrap capacitor. Later down the road you can try putting low value resistor in place of 0 ohm if needed to limit the slew rate at switch node.)

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LTC4449