TLV61225 boost - Short-circuit when powered from a CR2032 coin-cell battery

[MrZeroo00]

Hello,

I am powering my board using a TLV61225 boost IC with a CR2032 coin-cell battery (nominal voltage 3V when fully charged) to output 3.3V

The circuit draws about 20 mA under load (only 2 LEDs are powered up at a time). According to fig 1 of the datasheet, the boost should be able to source at least 160 mA

When powered from a coin-cell, the circuit draws the maximum amount of current the battery can provide and discharges it in seconds. Seems like a weird mode where the boost is short-circuiting the output (or the input?).

When powered from a bench power supply with a fairly high current limit (~ 200 mA) the circuit works perfectly and the regulation looks OK (at light load and under load). However lowering the current limit of the bench supply to around ~ 100 mA recreates the behavior of the coin-cell: short-circuit, the boost draws the maximum amount of current.

Here's my schematic (R11 is not loaded):

What could explain this behavior and how to fix it?

Thanks for your help!

[bktemp]

What could explain this behavior and how to fix it?

Datasheet page 7:

The device is controlled by a hysteretic current-mode controller. This controller regulates the output voltage by
keeping the inductor ripple current constant in the range of 200 mA and adjusting the offset of this inductor
current depending on the output load. If the required average input current is lower than the average inductor
current defined by this constant ripple, the inductor current becomes discontinuous to keep the efficiency high at
low load conditions.

So the controller turns the switch on until it senses 200mA, then turns it off again. If your power supply can't supply 200mA, the switch will stay on indefinitely.
Workaround:
The best one is probably use a different ic, that uses a limited turn on time. Maybe something like MCP1640.
If you add a large enough capacitor to the input and delay ENABLE for the ic, the capacitor will have enough energy stored to supply the 200mA for the ic to operate correctly.

[matseng]

Do you *really* need to boost the nominal 3 volts to 3.3? The '430 works down to 1.8 volts and the NFC chip is happy at 2.4.

[Codemonkey]

Coin cells have a very high internal resistance. You'll only be able to draw a few milliamps reliably from a CR2032 before the voltage drops significantly. Certainly anything over about 20mA is really pushing it!

[Fungus]

The circuit draws about 20 mA under load (only 2 LEDs are powered up at a time).

That's still quite a lot for a CR2032, you'll get quite a voltage drop due to battery ESR.

What could explain this behavior and how to fix it?

The booster draws current, the voltage drops.

The booster tries to draw more current to compensate, the voltage drops even more.

Repeat...

[Fungus]

Do you *really* need to boost the nominal 3 volts to 3.3? The '430 works down to 1.8 volts and the NFC chip is happy at 2.4.

Yep, just take the booster out and run the LEDs with 3V.