NXQ1TXH5 error

[ianxthomson]

Direct question for NXP support engineers unless someone else out there has already successfully used the NXQ1TXH5

Hi, I have a new board design using the NXQ1TXH5 and I have followed the datasheet and app note 100%. Unfortunately I have problems that I cannot diagnose:

1. Generally, the power transmitter starts up if the battery is low charge but when charging is complete or almost complete (difficult to determine this), charging stops and I get a flashing LED indicating a fault condition. I cannot diagnose which fault this is but I have to assume it is a receiver error, as it cannot be FOD or overtemperature (temp is low and power consumption is less than 1.5W). At this point, switching frequency is approximately 150kHz.

2. I have the NXQ1TXH5DB1401 eval (demo) board, and it will not start power transfer at all, and displays the flashing fault LED after attempting to establish connection for a few seconds.

In both cases I am powering directly from a 5V 2A lab power supply and am monitoring current, which is initially 800mA, and drops to 250mA or lower before cutting out.

3. There is an I2C interface on the chip which is described as "for assistance by NXP Semiconductors". Can the I2C interface provide log or diagnostic data to explain which fault condition is causing the problem? Please provide me with any necessary software and details of the I2C adapter I need to use.

4. My design uses small size 30mm coils from Wurth (Tx http://katalog.we-online.de/pbs/datasheet/760308101103.pdf , Rx http://katalog.we-online.de/pbs/datasheet/760308103205.pdf ). I have so far used the NXP demo board only with its standard large coil but I will also check with the 760308103205 Rx coil.

5. The design of our receiver (which uses BQ51013B receiver), when charging is complete, by-passes the battery so that the Qi receiver provides power directly to the hardware, and the battery is open circuit. The hardware switches between standby and operating modes, with approximately 80mA current pulses for a short time (tens of ms) - it is necessary that the Qi transmitter must continue to provide power all the time, and I expect trickle charge mode to support this. The datasheet says in "8.1.6 Charged state and trickle charge" that "When the NXQ1TXH5 receives a ‘charge status 100 %’ package (CS100 package) from the receiver, it changes the LED indication to charged state, but continues to operate in power transfer state". We already successfully do this with off the shelf USB charger pads.

Can you please help?

ian.thomson@omnisense.co.uk

NXQ1TXH5DB1401

[jcfmedical]

Old question. Same problem...

Everything works except when full charge arrive. It can works correctly during 5 ou 10mn and the led error..
This could not be a problem except the fact my product start a request as soon  it has been disconnected frome charge

[Stano]

Hi Ian,

you have mentioned, that you are using different coils - smaller from WE. I suppose, that the smaller one - round shaped is uased for TX side - the inductance is 6,4uH and oval shaped is used for RX side - inductance 11uH. The FOD could be caused also by TX coil, because it has low quality - internal DC resistance is 0.15 Ohm. I think it could be calculated a bit different FOD point and changed the external IC resistor for FOD.

In case you are using your application continually powered, it has to be connected directly to charged battery. Then the "end of charge" state will be properly detected (CS100 message sent from RX) and TX will not fall into fault state.

I will try this system usage later - I'm still waiting for such components for tests.

I think it could help you to solve your issue.

Best Regards,

Stano.

[ianxthomson]

Stano

I am reasonably happy with my solution. I do not think I need FOD, so it is probably not worth my time to investigate it further. However, let me know if you discover anything, and we might both learn something useful.

Ian

[ianxthomson]

I found a non-ideal solution. It seems that FOD (foreign object detection) is terminating power transfer. I have disabled FOD by connecting 0R from CNF3 (FOD_T) to CNF_IN. The problem may have been two-fold:

1. If Tx and RX coils are not well aligned, FOD interprets the resulting inefficient power transfer as the presence of a foreign object, so it stops transmission.

2. As charging nears completion, power in my receiving device comprises both battery charge current and peaky demand from the device hardware. I think the FOD system does not like this, expecting to see a steadily falling DC demand until charge termination, and falsely interprets it as positive foreign object detection.

It would be great to get confirmation from NXP or other users of these devices that this is the case. Anybody?