TLV61048: TLV61048

Hi DG,

This should not happen if nothing is wrong. Could you double check the value of R38 and R42 is correct?

What's your input voltage?

Regards,

Shipeng

Hi Shipeng,

Thank you for you answer. The value are good. I mean the resistors now have a tolerance of 1%. Is this to inaccurate? Can this produce a 0.4V lower voltage?

Best regards, Djordje

Hi DG,

If you solder the boards manually, it's possible that you pick wrong resistor. Could you change new resistors or you can measure FB voltage when power on to verify it?

Hi Shipeng,

the resistors are correct. The FB voltage is 0.743V.

Best regrads

Hi DG,

The typical FB voltage should be 0.8V, So I think the device is damaged, please change the IC. Be careful that VIN and EN pin maximum voltage is 6V, do not exceed it.

Hi Shipeng,

i will try it later. The V_in voltage is max. 4.2V and EN voltage is 3.2-3.3V.

Best regards, DG

Sure. 

Hi Shipeng,

you are right. The IC was damaged, but i do not know how. Thank you for your support, I need to investigate the cause of it, because the max input voltage is a li-ion battery (max. 4.2V).

Best regards, DG

Hi Shipeng,

one more question regarding the output signal quality.

• First picture output signal- no load (Output capacitor: 100uF Electrolyt Cap, 10uF MLCC and 1uF MLCC)

• Second picture output signal- no load (Output capacitor: 10uF MLCC and 1uF MLCC

Problem: without the extra electrolyt cap of 100uF the voltage ripple is much higher than with it. The problem of the first picture is, that in this condition the output signal generates a audiable, hearable noise. It is no very loud, but it would be nice to eliminate it.

Best regards, DG

Hi DG,

The light load behavior of TLV61048 is this. You can try to add a 10-100pF capacitor in parallel with R38 to improve that. You can try start from 10pF. Or If TLV61047 can meet your requirement, this device light load ripple performance will be much better.

Regards,

Shipeng

Hi Shipeng,

i tried it with the parallel Cap to R38. with 10pF the hearable sound stays the same and with 100pF it gets louder.

Any other suggestions maybe, not to use the TLV61047?

Best regards, DG

Hi DG,

Could you share SW waveform before and after parallel cap? If you parallel Cap on R38, the number of pulse in one time should be less.

Hi Shipeng,

i will try it later and report you. This acustic sound is only hearable at low output load. But i will report you.

Thank you for your help.

BR, DG

Sure. Thank you.

Hi Shipeng, 

attached you can find the comparison between only R38 and R38 || 10pF.

I can not see a big difference, except the number of pulses.

Maybe a feedback circuit with lower/higher resistors?

Best regrads, DG

And with 100pF the number of pulses per time is 3. So it get lower, but the sound is hearable (with 100pF its louder then with 10pF)

Hi DG,

You can adjust feedback resistors with higher value, or increase the capacitor to 220p or even 470p. The goal is making one pulse per time. But the device may get unstable before that, it depends on ESR of your e-cap. You can try it.

Hi Shipeng,

Thank you, i will try it. Can you also tell me, what is the best way to improve the thermal management? 

For this operation i need an output current of about 600mA. Input voltage: 3V - 4.2V and output voltage= 6V.

When i measure the temperature after about 1h of working the IC and Diode have a temp of about 78°C. It is a bit to high right?

Second question regarding the TS Pin: The battery pack is designed with an NTC for a overcharge temperature of 45°C. What happens, if the temperature reaches 45°C during operating mode, not charging.

Best regards, DG

Hi DG,

The temperature is normal, the device junction temperature can reach 125°C. Usually the diode also can reach 125°C. To improve the thermal, you can remove R41 to set Fsw to 600kHz.

Your second question is not my part, you need to ask others.

Regards,

Shipeng

Hi Shipeng,

thank you for the information,

I will try it with a lower SW-frequency. Is there any diagram with the efficency of output currents of more than 500mA?

The second question is answered by myself, i heated up the battery over 45°C and the device perform as needed

Best regards, DG

Does this temperatures have a big effect on the life-time of the part, or are this normally exceptable temperatures for this IC (more or less no difference if it works on 30°C or 80°C)?

Best regards

Hi DG,

I don't have more efficiency data at my side. The device lifetime is OK when junction temperature is lower than 125 degree.

Hi Shipeng,

ok, thank you.

Best regards, DG

Hi Shipeng,

i tried the same measurement without removed R41. The temperatures are more or less the same, maybe 2-3°C lower, but not a big improvement.

Anyway if it does not lower the life-time, it does not matter.

Best regards, DG

Hi Shipeng,

also with 220pF in parallel the sound exist. Now i try it with adjusted feedback resistors. Maybe the MLCC-Cap are not the best option for this kind of circuit?

BR, DG

Hi DG,

The sound is from MLCC, so if you can accept the ripple without MLCC, the issue is solved. The best solution is change to TLV61047, it will be one pulse at a time, causing less volage ripple on MLCC, so the noise will be lower.

Hi Shipeng,

The voltage ripple is to high (over 1V with a smaller load). Do you have any experiance about the EMC behavior of this IC, especially if we remove the MLCC and the ripple voltage is higher? To be honest, to change the IC now is a bit difficult, because it is an other footprint and pinning.

Best regards, DG

I tried also to remove the MLCC and soldered instead an electrolytic cap. The sound is there. Pretty strange, i don not know where it comes from.

Best regards, DG

If so, I advise you find the noise source first. Please check if it comes from inductor. Or even it comes from other device on the board.

No no, the sound comes from the IC and its circuit components. I will check this out, if the inductor is the noise source.

BR, DG