data/text/DLP4/900187

LM3630A: Why the inductance exists whistle ?

Part Number: LM3630A Hicompany team, My customer used LM3630A for Led driver . The Vin of LM3630A in their borad is 3.6V-4.3V and the number of led which maxium current is 10mA is 8. They found that the inductance exists whistle once the led lights. We will be appreciate ifcompany can help us to solve the whistle issue . Thank you! By the way. The following picture is their schematic.

Hi Troyson, For your schematic, you have floated the "PWM" pin? How to achieve dimming? You need to connect the"PWM" pin to achieve the current dimming. ( Or connect the "PWM" pin to a high level) Are you toggling the "HW_EN" pin? And since you just use one channel, have you disabled another channel? BR Sean

Hi Troyson, For your schematic, you have floated the "PWM" pin? How to achieve dimming? You need to connect the"PWM" pin to achieve the current dimming. ( Or connect the "PWM" pin to a high level) The dimming is controlled by I2C(Register_. Brightness A) Are you toggling the "HW_EN" pin? Yes.Customer input high level to enable the device . And since you just use one channel, have you disabled another channel? They do not connect the another chanel ,The led2 is floating Besides, we have tesed some waveforms. Hope it's good for you . We can find the frequency in Picture.1 & Picture.1 is <20khz which may cause the sounds Picture.1 The waveform in D3 (Diode)-2 pin Picture.2 The waveform in ILD1 pin Picture.3 The waveform in SW pin Picture.4 The waveform in SW pin Picture.5 The SCH

Hi Troyson, Picture 1-3 can't show now and you need to disable the channel two with the regs. reg0x00= 0x84; reg0x01=0x08. And have you read the reg0x0B? this is a fault register that may have some information. BR Sean

Hi Sean ， OK. Customer just used LED1.But they enable the 2 led chanel . So If customer float the LED2 pin .The deveice will work abnormally?

Hi Troyson, No, it will detect the open led and works abnormally. Please disable the LED2 with regs if they don't use this channel. BR Sean