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I am trying to help to salvage a design that doesn't meet a new specification. Circuit needs to drive a solenoid in relatively common fashion: High current pulse to actuate followed by reduced hold current. My colleague designed in a beautiful PWM solenoid driver chip TI DRV120 that does exactly what is needed. The caveat is that the achievable current is about 4x smaller than needed for the job.

Does anyone have an idea how to boost the current with a minimal number of external components feasible for a rework on the PCBA?

This is the block diagram of the IC:

Detail from DRV120 datasheet

Basically I am looking for a simple circuit acting as a "current mirror" of kind that would keep 25% of the solenoid current through the chip (to keep the feedback working) and sink 75% of the current straight to GND. Perhaps a circuit that would work like a PNP BJT with beta=3 as on my napkin sketch:

Concept

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  • \$\begingroup\$ It is PWM controlled. Looking at the block diagram, Rpeak and Rhold can set the duty to 100%, where the rail voltage decides the load current, unless limited. Sorry, that I have not read the datasheet through, if you cannot get enough current at 100% duty caused by the driver output, then you may just add another switching FET. \$\endgroup\$
    – jay
    Commented Sep 24, 2021 at 15:22
  • \$\begingroup\$ @jay Thanks for the comment. I certainly studied the datasheet first before posting my question. Perhaps I should have stated that I need about 4x peak current than what the DRV120 is rated for. The max peak current per datasheet is 250mA. \$\endgroup\$ Commented Sep 24, 2021 at 18:39
  • \$\begingroup\$ What is the supply voltage? \$\endgroup\$
    – bobflux
    Commented Sep 25, 2021 at 9:38
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    \$\begingroup\$ Might be solved by now but check out the DRV110. It's very similar except it allows an external FET \$\endgroup\$
    – c10yas
    Commented Apr 30, 2022 at 1:58

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Perhaps a circuit that would work like a PNP BJT with beta=3 as on my napkin sketch:

Beta 3 can be achieved using 3x current mirror, ignore the components value.

schematic

simulate this circuit – Schematic created using CircuitLab

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