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Cold Start Charge Pump

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pancho_hideboo

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Ultra low Power Energy Harvester with MPPT and Charge Management IC, ADP5091/ADP5092 of ADI has cold start-up circuit.

https://www.analog.com/media/en/technical-documentation/data-sheets/ADP5091-5092.pdf

This IC operates in three stages:
(1) cold start
(2) asynchronous boost
(3) synchronous boost

Cold start can be implemented by ring oscillator.
Then Ring oscillator drive High and Low Side MOSFET for booster.
In this case, voltage boost is done bu external inductor during cold start.

However, Cold start block is denoted as "Charge Pump" in ADP5091/ADP5092.
So is this charge pump like Dickson Chargepump ?
I think external inductor is not used during cold start.
High and Low Side MOSFET for booster are dead during cold start.

TI also have similar IC, BQ25570.
https://www.ti.com/litv/pdf/slusbh2g
It seems High and Low Side MOSFET for booster are active during cold start.

How do you think this Cold Start Charge Pump work in ADP5091/ADP5092 ?
 

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Last edited:

Looks to me like probably a "hiccup mode" boost
converter tries to pump the battery on the other side,
and the sync rect FET gate supply before that. A ring
osc might be a bit too high frequency but a micropower
ramp / comparator / SRFF oscillator can be made to
run low and slow.
 

Regular CMOS logic won't be able to run from 0.38 V. Special circuit, preferably with depletion mode transistors is required for the cold start function. If the schematic in ADP5091 data sheet isn't intentionally misleading, it may show a self oscillating circuit utilizing the boost inductor.
 

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