LT8336 in shutdown mode

Hello,

the LT8336 ia synchronous Boost regulator, hence it 'features' a DC path from input to output, even when part is in shutdown and even when the catch diode is replaced by a FET. Reason is the parasitic body diode of the synchronous FET.

If this behaviour is undesired you would need a Boost with explicit 'output disconnect' feature (LTC3121, but different VIn, IOUT performance).

2nd option would be the SEPIC topology, which offers a coupling cap and has therefore no DC path from input to output.

Hi Markus,

Shutting down the controller while still under Vin=12V and DC loaded (Iout = 0.5A for example) would damage the controller?

Thanks,

Nir

Hello,

as the body diode of the top-FET would 'see' this 0.5A load current with a certain drop (much higher than normal diodes) power loss in the LT8336 might get large with possible bad consequences for the LT8336. I would not allow this scenario to the application or at least limit the load current during shutdown to smaller (and tested) values.

kind regards

Markus

Hi,

So I guess there is no option but to use a load switch at VIN or VOUT in order to achieve a full shutdown...

Thanks for your reply.

Nir 

Hello Nir,

to avoid this additional work I would recommend to use a DC/DC regulator in a SEPIC topology, this requires a 2nd (or coupled inductor), but features a 'no DC path' between input and output. Hence you have a full shutdown without any additional load switch.

LT8330, LT8362 or LT8365 feature your voltage and current range, low IQ and AEC-Q100 qual.

kind regards

Markus

Hello Nir,

to avoid this additional work I would recommend to use a DC/DC regulator in a SEPIC topology, this requires a 2nd (or coupled inductor), but features a 'no DC path' between input and output. Hence you have a full shutdown without any additional load switch.

LT8330, LT8362 or LT8365 feature your voltage and current range, low IQ and AEC-Q100 qual.

kind regards

Markus