TPS61165: Fig.16 External PWM Dimming Network

Takashi Yamaguchi

Part Number: TPS61165

Hi team,

I have a question about the Fig.16 circuit. I think that this circuit is for analog dimming from PWM signals that are below 5 kHz. If customer has 5k to 100kHz PWM, they can use Fig.8 circuit. Is my understanding correct?

Also, Fig.16 states that "Drive Three High-Brightness LEDs". If customer wants to drive the LEDs with High-Brightness(High current), should customer use the Fig.16 circuit? If so, could you tell me the standard(threshold) of the LED current(mA)? For example, if the ILED is more than 300mA, Fig.16(External PWM Dimming Network) is recommended.

Regards,

Yamaguchi

over 4 years ago

0 Hardy Wu over 4 years ago

TI__Genius 12915 points

Hi Yamaguchi-san,

Fig.16 is a way to achieve PWM dimming and the frequency cannot be too high, since there need some time for loop stability. PWM dimming or analog dimming is for output side. PWM dimming means changing output duty cycle to adjust output current, while analog dimming means changing peak current level. The inputs are all PWM signal. I think the decision of choosing PWM dimming or analog dimming is decided by whole system requirements, but not the current setting.

For ILED range, it is determined by VIN and VOUT. Assuming the efficiency is 90% and there are 100mA current ripple on inductor. Since the current limitation of internal switch FET is 1.2A, the max output current is around VIN*(1.2A-0.1A) * 90% / VOUT.