TPS61021A: Pulsed Currents on Demo Board

Gregg Haensgen

Part Number: TPS61021A

I've been evaluating a few different boost regulators for a new project and I'm confused by a few things I'm seeing. When I look at the graphs the efficiencies of the regulator, they don't look that bad in the graph but when I measure the boosted pulses the current is higher than I was expecting. Just for reference in this situation I am boosting what should be a ~140mA pulse at 3.3V. I'm wanting to use a supply from 0.8V to 1.6V. Below are the currents I'm reading with the TPS61021A boost regulator demo board.

310mA at Vin=1.5v
482mA at Vin=1v
576mA at Vin=.9V
659mA at Vin=.8V
745mA at Vin=.7V

If I look at the datasheet it says the regulator should be nearly 85% in this range. It does start dropping off at higher currents but these numbers seem high. My initial thought is that the efficiency is typically measured at a relatively steady state output and maybe the pulsed demand at the output is causing the regulator to have to compensate for the rapid change in demand at the load?

over 5 years ago

0 Helen chen over 5 years ago

TI__Mastermind 40080 points

Dear Sir,

Actually, for the TPS61021A, the efficiency at 1V is around 80%, while the efficiency at 0.7V is much lower than 1V, which is even less than 70%.

What is your 140mA pulse current looks like? The duty and the duration?

0 Gregg Haensgen over 5 years ago in reply to Helen chen

Prodigy 140 points

The 140mA pulse is roughly 400ms and very infrequent. I understand the efficiency is less at 0.7V but still the numbers of what I was getting at the other voltages I mentioned don't make sense to me.

0 Helen chen over 5 years ago in reply to Gregg Haensgen

TI__Mastermind 40080 points

How did you test the efficiency? do you test the onboard voltage?

0 Gregg Haensgen over 5 years ago in reply to Helen chen

Prodigy 140 points

Hi Helen.

I am measuring this with an N6705C DC Power Analyzer in terms of current. I just ran another test in which I am powering with the analyzer at different input voltages and showing the current pulse to the input of the TPS61021A dev board and then showing the current pulse at the output of the regulator using it as a current sense (ammeter) to my load which is a roughly 140mA pulse for my transmitter. As you can see when I apply 1.2V to the input of the regulator I am seeing roughly 420mA (yellow trace) into the regulator.

At the same time I am seeing the expected load correctly at 134mA (greeen).

Thanks.

Gregg

0 Helen chen over 5 years ago in reply to Gregg Haensgen

TI__Mastermind 40080 points

Hi Gregg,

When Vo=3.3V, Io=0.14A, eff=0.85, Vin=1.2V, the estimated Iin=(3.3*0.14)/(eff*Vin)=450mA. So it is OK to read a 420mA current pulse at the input side with a higher than 85% effciency.

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TPS61021A: Pulsed Currents on Demo Board