florent simonnot

L6491 max duty cycle and Vboot behavior

Discussion created by florent simonnot on Apr 21, 2017
Latest reply on Apr 26, 2017 by florent simonnot

Hi.

 

I'm currently using the L6491 to perform a current-mode capacitor charger.

Structure is simple : a resistor is in line inserted after the self and before the capacitor.

An high speed comparator with programmable hysteresis deliver the command to Hin and Lin (tied together). Both frequency and duty cycle are variable, it's funny !

but...

 

two questions :

1/

I have a good behavior while duty cycle is quite low, the voltage output is far away voltage input.

since duty cycle reach 86% the driver stops (at this moment f=89Khz)

Quite normal I think, there is a undervoltage lockout according the Vboot monitoring.

Unless...

2/

is there a duty cycle limitation ? (I think the limitation is effectively comming from Vboot lockout)...

 

 

best regards...

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