TPS2546: CDP mode fault pin status

Hello Srekanth,

Are you sure you are configured in CDP mode (no jumpers on CTL pins)? The current limit setting for CDP mode is ILIM_HI not ILIM_LO, so there should be no difference in adding a resistor to that pin when you are in that mode. Also, how are you powering the EVM? By an external power supply or being plugged into a laptop?

Hi Adam,

The CTL and ILIM_HI pins are connected to 3.3V through 0 ohm resistor . In our application phone/Tablet will be connected to TPS2546 and the supply (5V) is provided through Buck converter.

Thanks,
Sreekanth

Sreekanth,

Can you look to see what the voltage is on VUS, as well as what the current is comping out of VBUS? FAULT is designed to trigger during an over temperature or over current event. I doubt there is a over temperature event happening so it would have to be over current. There may be large current spikes that the TPS2546 is detecting as an over current event, and triggering the OCP feature.

Also, include your schematic so I can take a look at how you are implementing the TPS2546

Hi Adam,

The voltage on VBUS is 5.14V and the current drawn from VBUS is ~1.1A. Please note I have measured the current using multimeter. We are using a buck converter to convert 12V to 5V.

Thanks,
Sreekanth

Hello Sreekanth,

Those are correct value and should not be causing an error. However, I just re-read one of your previous comments, and ILIM_HI cannot be connected to 3.3V, but instead needs to be connected via resistor to GND. I would try fixing this connection and see if it fixes the FAULT issue.

Hi Adam,

In our schematics we have connected ILIM_HI to ground through a resistor which is setting the high current limit. As the fault pin was toggling when the ILIM_LO pin was open, I added a resistor to ILIM_LO pin. ILIM_SEL pin is pulled high to 3.3V.

Is ILIM_SEL which is connected to 3.3V causing the issue? In our schematics we are using 2 more TPS2546 where they are working in auto DCP mode and the ILIM_HI pin is connected to ground through resistor for 2.1 and 2.4A current limit.

Thanks,
Sreekanth

Sreekanth,

I doubt that the 3.3V is causing the issue, but you can try connecting it to the 5V rail and see if that helps. The STATUS pin works as it should on the EVM when programmed to CDP mode. Here is a screenshot I took using the TPS2546 when trying to charge my iPhone 6s. The STATUS pin goes low as expected, and goes back high when the iPhone is unplugged.

I'm still confused as to what your actual problem is. Is the STATUS signal going low when nothing is connected? Is it not going low when something is connected?

Also, can you include your schematic for me to take a look at?

Hi Adam,

Our issue is not with status pin but with fault pin.

When we connect the phone to TPS2546 the fault pin is immediately going low, where the fault pin should not go low unless there is over temperature or over current fault.

In the initial circuit ILIM_LO pin was open and the fault pin was asserting low for some time and going high, now we have connected a resistor between ILIM_LO pin and ground and the fault pin goes low when we connect device for charging.

Thanks,
Sreekanth

Hello Sreekanth,

This does make sense as the current setting during CDP mode is ILIM_HI, so changing the resistor tied to ILIM_LO should not have an effect on the current setting. I would suggest checking to make sure that:

1. The TPS2546 is in CDP mode. Meaning that CTL1, CTL2, CTL3, and ILIM_SEL are all pulled high

2. That the resistor you are changing is tied to ILIM_HI

3. That the pads for pin 15 and 16 are not shorted together

Also if you do not need to use ILIM_LO, I would suggest removing it. It sounds like your problems started to occur once you included ILIM_LO into your design. If you do not need it in your system, I would remove it.

Hi Adam,

I can confirm that CTL1, CTL2, CTL3 and ILIM_SEL are pulled high. Pin 15 and 16 are not short.

I have attached the schematics for your reference. In the schematics the ILIM_LO pin is open, for testing I have added a 3K resistor.

Thanks,

Sreekanth