LM3630A: Request for review on the applicability (number of LEDs per string)

MJ Jeon

Genius 5240 points

Part Number: LM3630A

Hi, Support Team

A customer wants to operate by applying LM3630A to the e-book E-INK EPD Frontlight led.

Please answer the following two inquiries.

Question 1. When using LED MAX CURRENT=10mA, how many LEDs can be applied to one string?

-LM3630A datasheet: 10 LEDs based on 20mA

-Backlight LED to be used: Iled=10mA, LED1=11, LED2=12 will be applied

Are there any problems with the above application?

[EPD LED Electrical Specification]

[Calculation of PD based on LM3630A specification, number of LEDs = 10ea]
In case of applying VIN=3.6V, Iled=20mA, VHR =160mV, number of LEDs 10
PD=ILED X number of leds X VHR=20 X 10 X 0.16 =32mW

[Calculation of PD based on customer use, number of LEDs = 12ea]
When Vin MAX=4.5v, IledMAX=10mA VHR 160mV, 12 LEDs are applied
PD=ILED X number of leds X VHR=10 X 12 X 0.16 =19.2mW

Question 2. How should I control the OVP voltage when used as above?

I would like an answer as soon as possible.

Thanks.

Regards,

over 3 years ago

0 Hardy Wu over 3 years ago

TI__Genius 12915 points

Hi MJ,

1. When using LED MAX CURRENT=10mA, how many LEDs can be applied to one string?

It depends on the LED forward voltage when 10mA current applied. Voltage on LEDx pins need to be above headroom voltage 250mV to sink precious current. And VOUT can support up to 40V. Based on the LED information, 12ea LED with 37.2 max VLED can be supported.

2. How should I control the OVP voltage when used as above?

OVP threshold need to be above than headroom voltage plus LED forward voltage. In your case, it should be set as 40V.

Power management

Power management forum

LM3630A: Request for review on the applicability (number of LEDs per string)