TLV61046A:Does not stabilize output with input less than 3,0V

Hi TIAGO,

The expert is out of office today and will return tomorrow.

Sorry for the inconvenience.

Best Regards,

Fergus

Hi Tiago,

From the schematic you attached, the max Iout when the Q3 is on is around 0.12A, not 40mA. Could you confirm?

Please also measure the Iout and add the Iout waveforms, together with the Vout especially when Vin = 2V.

Regards

Lei

Hi Lei, thanks for the answer,

I'll provide the waves.
But, even if the peak current is 120mA, the TLV should be able to withstand it, right?

Hi Tiago,

When works in 2V Vin to 12V Vout, the max Iout is around 70mA only. So if the Iout is 120mA, the Vout will be pulled down significantly.

I attached a max Iout calculation tool for your reference.

Max Iout Calculator.xlsx

Regards

Lei

2V input voltage and 12V output waveform: 

Output voltage 12V and current ~50mApp (1mV/10mA non-invasive probe)

Input voltage 3.8V. Output voltage 12V and current ~50mApp (1mV/10mA non-invasive probe)

Hi Tiago,

Thank you for providing the waveforms. I'll further check and provide the feedback to you early next week.

Regards

Lei

Hi Tiago,

As my check on EVM with 3 different chips, when 10µH inductor is used, the 50mA Iout can be supported when Vin = 2V and Vout = 12V.

Following is the load transient waveforms for your reference. The 10µH inductor is FDSD0420-H-100M, which is used on the official EVM. The black Vout was measured when Vin = 2V, the grey Vout was measured when Vin = 3V. The transient behaviors are normal and almost the same for both conditions.

Could you help double confirm what's the used inductor, 4.7µH or 10µH?

Please let me know if there any concerns or updates.

Regards

Lei

Hi Law

I use the SP43-100K Codaca. However, I have already tested it with the EVM inductor and other models. What was different about this test? I ask this because Raphael told me that you could simulate the same problem I'm having...

Hi Tiago,

I measured on EVM and see similar phenomena at Vin = 2V when 4.7µH inductor was used. That's what I feedback to Raphael at first.

Then I changed the inductor from 4.7µH to 10µH, the big Vout drop disappeared. When 10µH inductor was used, the behaviors were almost the same when Vin = 2V and Vin = 3V.

So I'd like your help to confirm whether the currently used inductor in your application is 10µH or not.

Could you also help confirm the following 2 items?

1. Minimum Vin: 2V or 2.5V?
2. Maximum Iout: 40mA or 50mA?

Thank you.

Regards

Lei

Hi Lei

My current inductor is 10uH (Codaca SP43-100K)

Minimum Vin: 2V

Maximum Iout: 50mA

Hi Tiago,

Even for the worst conditions that the frequency = 859kHz (min), efficiency = 65%, peak current limit = 621mA, inductor = 9μH, TLV61046A can still output 55mA when working in 2V Vin to 12V Vout. This matches what I observed on EVM.

Well, you had different observations at your side.

If available, could you ship 2 boards to me for further check?

Regards

Lei 

Hi Lei, I'll wait for a new PCI version to arrive to test the layout. I will return as soon as possible with information.

Thank you for now.

Hi Tiago,

Thank you for your information.

Just let me know if you need any support I can provided.

Regards

Lei