Post Go back to editing

[SOLVED] Using Boost-Off to disable boost mode feeding only battery voltage to load

Category: Hardware
Product Number: LTC4040

Hey all,

 I'm tinkering with the LTC4040 for an application where it's desired (and able) to feed the load with the battery voltage directly (to an SRAM holding configs/values).

The load is so low - the boost switcher uses more current. (Ha!)

Anyway - so it's desirable to just turn the boost off when in backup mode.

When I do this - I only get about 800mV (or so) -- not the current voltage of the Lithium cell connected to the LTC4040.

Is there something else that needs to be done in terms of the the FB voltage set pins (BSTFB)?

Or am I misunderstanding how BSTOFF works in terms of supplying load? (i.e. it really turns off the boost circuit including disconnecting the Lithium cell)

Thanks,

 -Ben

Edit Notes

UPDATE: Spoke with Tech Support -- the answer is: If the boost-converter is disabled, then the power-path from the battery to the load (Vsys) is also disconnected (more or less) This makes the LTC4040 essentially a battery charger. So plan/design accordingly.
[edited by: BenKamen at 11:55 AM (GMT -4) on 22 Aug 2024]