Pico buck alternatives

Currently I have a system with a low(9V) and high(13.5V) voltage mode and I want to incorporate LEDs signaling those modes.

I’ve looked at the Picobuck so far, but want to stray away from dev boards and figure out a better mass production solution.

One method I have in mind is to use my existing setup with relays and use high voltage leds.
The other method is figuring out a cost effective way to use a single RGB led to change colors indicating modes.

Hello _nivek,

Thank you for your inquiry and welcome to the community!

What you’re describing sounds like a 2 element window comparator for under and over-voltage detection.

The following device can take anywhere from 1.8V to 18V source voltage. You just gotta figure out what values you need for the voltage divider to turn the outputs on when you need them.

Click here for MFG PN: TPS3700QDDCRQ1 Digi-Key PN: 296-40743-1-ND

Here is an adapter board for prototyping with the SOT-23 package size:

Click here for Prototyping Adapter Board Digi-Key PN:1568-1098-ND

Click here for breakaway header to go with your prototyping adapter board PN: S1212EC-40-ND

Awesome thank you for the response!

edited: ignore that last part I see the current output of the comparator is low? so I can use 5v leds?

This device takes 14uA of supply current and the inputs use a voltage divider that’s in the Mega ohm range, it’s power usage itself would be pretty minimal, most of the power would be used by your leds.

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To answer your question on LEDs, the outputs of this device can drive up to 40mA, when they’re on they become active low, otherwise known as sinking current to ground through a pull up resistor.

If you’re thinking of driving low current indicator leds directly you could put them in series with a resistor wired directly up to the voltage source rail.

Another idea that might be worth trying is outlined below. The idea here is that as the supply exceeds some threshold equal to the zener voltage plus the Vbe of the transistor, the transistor turns on and shorts out one of two LEDs in a bi-color package. Using a red+green LED then, you’d have something like an orange indication when supply is below threshold, and either red or green when above. The current source could be a cheap linear driver like something in the BCR420 family, something similar built out of discretes, or whatever else gets the job done.

This would be a less precise approach than that which Kristof suggests and likely somemewhat larger in terms of board area, but has the advantage of using cheap, easily-substituted components.


Is a voltage regulator best practice? Vdd would be about 13.5v from a car battery source.

The V-Reg is just in the example circuit as the load in this situation. That schematic was provided to show the voltage divider on the inputs.

In your case your load would be an individual resistor and LED tied in series from your voltage rail to each output.

Gathering from your information and rick’s, is there any components that exists that combines comparator and constant current led driver functionality?