• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 1897 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Overheating on boost converter of TPS65101

Di Wang
Expert 1740 points
Other Parts Discussed in Thread: TPS65101

Hello,

I'm designing a LCD driver with TPS65101. Below is the SCH. ENR is pulled low and inductor is 4.7uH

When the LCD screen is not connected (no load), the SW1/SW2 waveform is as below shows. It looks abnormal and the duty is 68% which is CCM. Does it mean SUP pin consume a heavy load and the boost converter is not DCM even without the LCD screen connected?

After I connect the LCD screen, the SW waveform looks normal, but case temperature rise of TPS65101, inductor and schottky(1N5819) is about 60℃! I changed some types of the inductor, but no improvement. I didn't find the recovery time of schottky(1N5819) in the datasheet. I also found the fsw of the boost converter with LCD screen connected is a little higher than no load(1.8MHz and 1.6MHz).

From the spec of this LCD screen, AVDD requires 10V/200mA. There is a large heat sink area in PCB layout for TPS65101.

I need your information on two points.

1. Could you confirm on the EVM that, without LCD screen (AVDD is no load), the boost converter works in CCM(SUP is heavy load)?

2. Any idea I could try to locate the issue?

Thanks.

  • 0
    TI__Guru 58225 points

    Hello Di Wang1,

    1. The boost converter of TPS65101 is always working in CCM. The switch from SUP to SW will act as conducting switch if the current in the inductor is getting negative. So SUP is not a heavy load, but the internal switch is used as synchronous switch.

    2. Most probable the VGH charge pump is causing the high temperature. You have a capacitor connected to the C2x pins which means the charge pump is working as a voltage tripler. So the charge pump tries to generate 30V but is linearly regulated and dissipates the not needed power, so the power dissipation in the VGH charge pump is around 10V times the output current on VGH. Is it absolutely necessary to have 20V on VGH? If you could live with a slightly lower VGH voltage, you can remove the cap on C2x and connect MODE to GND. Then the charge pump is working as a doubler and dissipates almost no power.

    The power dissipation is lower as well, if you increase the output voltage on VGH, so this could help to reduce the temperature as well, if you cannot decrease the voltage on VGH, try to increase it to the maximum.

    Best regards,

    Brigitte