TPS63030: Ultra-low idle current

Hi Milos,

Thanks very much for your support. I connected PS/YSNC to the ground and put 100k (also tried 1k, 10k, 1M too) resistor to the enable pin. And I put a 10uF pol-capacitor to the output. Now the idle current goes down to the 500uA but still high. I need to go below 100uA and TPS63031 should go under 50uA as you said.

I recorded a video about what I did. I want to be sure if I need to change IC.

PS: Sorry, I remember wrong the IC model. It isn't TPS63030, it is TPS63031 3.3V output.

Hi Salih,

Thanks for the update, I will come back to you by the end of the day.

Best regards,
Milos

Hi Salih,

One note first. The output capacitor should really be a ceramic type. An electrolytic/tantalum capacitors have much higher ESR and ESL and are not suited for this converter. They are fine as an addition to ceramic capacitor, as a bulk storage capacitance, but at switching frequencies, they are not capacitors anymore. Additionally, make sure the output capacitor is as close as possible to VOUT, you can check the recommended PCB layout in the datasheet. You can also post your PCB layout here for review. 

Back to your problem, can you please try removing the output TVS diode? At 3.3 V your TVS diode might already conduct a few hundreds of μA. 

Best regards,
Milos

Hi Milos,

I took off TVS diode and tantalum capacitor. I have tried with an 10uF, 3x10uF ceramic close to the IC (parallel to the C14) and without ceramic . 100nF (C14) is already placed on the board close to the IC. Now the IDLE current is 380uA. It is getting better but still far away.

PS: The package of the components such as C14 are 0603.

Hi Salih,

I'm just double-checking, there is nothing else assembled on the board, therefore there is nothing connected to the output of the converter except for the output capacitors?

I would try a few things:

1. Can you try putting an inductor with a higher saturation current (and lower DCR). The one you are using is on the small side. It might happen that it saturates in PFM mode. In PFM mode the converter operates in short bursts, with the inductor current pulses typically above 200-300 mA.
2. To get correct input current measurements, make sure you have a buffer capacitor between the power supply and the input of the converter. Check chapter 2.2 in this app note for the explanation:
   http://www.ti.com/slva236-aaj

Also, I have a few remarks for the PCB layout:

1. C14 should be closer to VOUT, and the GND end of C14 should be directly connected to the thermal pad. Please check the recommended layout in the datasheet, Figure 24. I can't stress enough how important the PCB layout is for a switch-mode converter.
2. Connect the GND pin to the PGND/thermal pad directly in the top layer.
3. C3 should be placed closer to VINA pin, but this is not that critical.

Best regards,
Milos

Hi Salih,

Is there any update, did you manage to try my suggestions?

Best regards.
Milos

Hi Milos,

Sorry about late response. I have just received new components for testing. I put a bigger current inductor and Iq went up to 710 uA. And also tried bigger and lower inductors as well. Nothing good news.

Yes it is completely empty except power circuit. I decided to re-design with several chips. It is hard to fix traces on the current board.

(DIP resistors are only for simulating the rest of the board. I have checked with and without theese resistors.)

Hi Salih,

Can you please take the scope plots of Vin, Vout, L1, L2, for Iout = 0?

And just to check, did you always use the same device, have you tried replacing the TPS63030 unit?

Best regards,
Milos