LP8866S-Q1: LP8866SQDCPRQ1

Tarun Vemu

Prodigy 20 points

Part Number: LP8866S-Q1

Hi TI Team,

We are using 2 FB Divider Using Three-Resistor Method with FB resistors as following:

R1=51.1K, R2=2.2K, R3=17.4K.

This setting is to drive a 5 channel TFT which requires worst case voltage of 42.73V.

With this setting we are observing LP8866S-Q1 output voltage to be fluctuating between 50.7V to 37.8V and TFT strings are not powering up.

Could you please let us know the reason for this as soon as possible and any suggestions in feedback resistor changes?

Thanks, and Regards,

Tarun.

3 months ago

0 Tarun Vemu 3 months ago

Prodigy 20 points

Can we make a resistor setting such that Calculated Output voltage is above 48V?

0 Zhiqian Wu 3 months ago in reply to Tarun Vemu

TI__Mastermind 19730 points

Hi，Tarun
Could you pls kindly share the schematic and test point of waveform？

0 Tarun Vemu 3 months ago in reply to Zhiqian Wu

Prodigy 20 points

Hi Zhiqian, I sent to you through private message.

Thanks.

0 Zhiqian Wu 3 months ago in reply to Tarun Vemu

TI__Mastermind 19730 points

Hi, Tarun

Could you pls increase the R2 to have a try? the ratio between R1/R2 is too high for our device.

0 Amal K Moncy 3 months ago

Prodigy 40 points

Hi Zhiquian Wu,

Can you help us understand the question from Tarun?

"Can we make a resistor setting such that the Calculated Output voltage is above 48V?" How the system will operate?

0 Zhiqian Wu 3 months ago in reply to Amal K Moncy

TI__Mastermind 19730 points

Hi, Amal

It is the first time to see the question from Tarun as you said. In the previous, we talk about the abnormal waveform in boost output.

For this question, as our device is a controller, if the external like FET can afford higher than 48V. We don't recommend to do like this, but our device can support this case, but need to disconnect the DISCHARGE pin. Besides, here is a risk, once the LED string is short, then device may destroy on OUT pin due to the high voltage.

Power management

Power management forum

LP8866S-Q1: LP8866SQDCPRQ1