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BQ51003

Part Number: BQ51003
Other Parts Discussed in Thread: TIDA-00318, TIDA-00669

We are using Wireless charging IC BQ51003. Our device is designed for 500mA and the ILIM is 330 ohms. Without connecting load,the voltage at  Vrect is 6.5 - 7 V and Vout  is 5v. When connecting the load of 10 ohms at Vout of wireless charging IC there is a voltage drop at Vrect and Vout,the measured voltage at Vrect is 3.6V and Vout is 3.3 - 3.5 V. This same occurs when we change our device for 350 mA and ILIM for 560 ohms. But when we change our device for 250mA and ILIM for 845 ohms,there is no voltage drop at Vrect and Vout during the load condition.what will be the reason for the voltage drop when designed for 550 mA and 330 mA. We need our device to be work at 550 mA.

  • Hello

    What can you tell me about your RX coil and tuning?

    Also what value FOD resistor are you using, FOD pin gnd?

  • RX coil WR222230-26M8-G

    FOD pin is connected to Microcontroller

  • Hello

    the FOD pin needs to be connoted to ground thru R-FOD, see figure 32 in data sheet.  The RX will report received power as a function of output current, ILIM current develops a voltage across R-FOD.  This is converted into a digital value sent to TX.

    WR222230-26M8-G coil is small and will work well below 500mA.  Resonant caps need to be tuned  to about 100nF.

  • Hello

    Thanks Bill for your idea.

    Actually we need our device to be worked in 500mAh current,is there any schematic for BQ51003 to work in 500mAh.

  • Hello

    Some designs that can be used as a reference:

    1.) Evaluation board -- www.ti.com/lit/pdf/sluuau8

    2.) TI Reference design TIDA-00318  -- www.ti.com/tool/TIDA-00318   

    3.) TI Reference design TIDA-00669 -- www.ti.com/tool/TIDA-00669

  • Hello

    Thanks Bill Johns for your reference

  • Can we keep the FOD as floating(i.e not connected)?.

  • Hello

    Floating FOD will cause problems.

    Need to connect to ground thru resistor and resistor between ILIM and FOD, see application section of data sheet.

  • Hello

    We have designed a device with wireless charging technique using Bq51003 and receiving coil  WR222230-26M8-G.In the above configs we are facing some problems while charging.

    One major issue is that charging stops suddenly for more-than 10mins and it continues to charge after that time,what maybe the reason?.

    While testing we are removing and placing our device in the charging pad for multiple times,after this testing it stops charging for 5 mins.can i know the what is the reason?

    Also i have to know the above kind of testing will cause any damage to the components?

    Temperature rises up-to 60 deg Celsius while charging,is there any possibility to reduce the temperature?

    Regards

    Jagan K

  • Hey Jagan,

    I too have same problem,when we test our device in charging pad ,charging stops suddenly and it takes some time to recover.Can some one suggest what could be the solution?

    What must be the minimum voltage rating of capacitor C1 C2 in the input side of  bq51003?

    In evaluation kit they used three parallel capacitor in the input,shall we use one capcitor in that place instead of three capacitor?

    Bill ,what is FD and Fs and Ls and Ls' in C1,C2 calculation?

  • Hi Jagan K

    One major issue is that charging stops suddenly for more-than 10mins and it continues to charge after that time,what maybe the reason?--Bill J -- This is probably controlled by the Transmitter, the receiver will tell transmitter to turn off using EPT packet.  But the Transmitter will decide when to power the receiver back up.  Check what the transmitter is doing during the 10min is it powering the receiver at least 80mS?

    While testing we are removing and placing our device in the charging pad for multiple times,after this testing it stops charging for 5 mins.can i know the what is the reason? -- Bill J -- Tell me more about this test?  Also check the voltage at RECT during this time, what are you seeing?

    Also i have to know the above kind of testing will cause any damage to the components? -- Bill J -- I need a better description of the test.

    Temperature rises up-to 60 deg Celsius while charging,is there any possibility to reduce the temperature? -- Bill J -- Yes several thing can be done.  First test would be to separate the coil from receiver and extend it on wires.  Only place the coil on TX and check temp.  If the thermal rise is due to AC loss temp should go down, solution would be to add shielding.  If the thermal rise is about the same it is due to conversion loss in the circuit and need to look at where power is dissipated at.

    Regards

    Jagan K

  • Hi Sowmily

    I too have same problem,when we test our device in charging pad ,charging stops suddenly and it takes some time to recover.Can some one suggest what could be the solution?-- Bill J - Check the voltage at RECT to see if the TX is trying to power the RX on, need a pulse of at least 80mS.  Some TX will turn off for 10min if they get a charge complete or fault from the RX, then remove power and do not try and turn on.

    What must be the minimum voltage rating of capacitor C1 C2 in the input side of  bq51003?---Bill J -- 25V

    In evaluation kit they used three parallel capacitor in the input,shall we use one capcitor in that place instead of three capacitor?---Bill J - No, the ESR and power loss will be higher. 

    Bill ,what is FD and Fs and Ls and Ls' in C1,C2 calculation?  --- Bill J -- See data sheet section 9.2.1.2.2 Series and Parallel Resonant Capacitors, also equation 6 of that section.

  • Thanks for your response

    2.Test is like we are placing the device with Receiver coil in wireless pad for charging ,we will remove the device from pad intermittenly and we will place the device again for charging at that time the device is not charging it takes average of 3 - 5 minutes for charging. Sometimes it's not charging,after the battery fully drained it charges again.

    During that time Voltage at VRECT is 3.5 - 4 V and it's not constant voltage.

    Regarding Heat issue,we tested like you said at that time there is no temperature rise.

    Regards

    Jagan K

  •  Hi Jagan K

    "During that time Voltage at VRECT is 3.5 - 4 V and it's not constant voltage." -- Bill J -- Send scope capture of the RECT voltage, this is a very good indication of what the TX and RX are doing.

  • Also

    "Regarding Heat issue,we tested like you said at that time there is no temperature rise." -- Bill J -- AC field from the TX is heating PCB / Battery and other metal in the device.  Try shielding the metal using magnetic shielding material similar to  Wurth Electronics 354002.