The LM3421 is the only constant off time LED driver IC in the world which has an internal error amplifier.
Why is there only one such IC in the world?
LM3421 DATASHEET:
https://www.electro-tech-online.com/custompdfs/2013/09/lm3421.pdf
Constant off time is THE answer to driving long series strings of LEDs from low input voltages, because 'constant off time' lets you do high step up ratios without needing slope compensation, and is devoid of the maximum duty cycle limitations which are prevalent in most constant frequency PWM controllers.
The HV9910B is a constant off time controller , but does not contain in internal error amplifier.
HV9910B datasheet:
https://www.electro-tech-online.com/custompdfs/2013/09/HV9910B.pdf
Why is there only one such IC in the world?
LM3421 DATASHEET:
https://www.electro-tech-online.com/custompdfs/2013/09/lm3421.pdf
Constant off time is THE answer to driving long series strings of LEDs from low input voltages, because 'constant off time' lets you do high step up ratios without needing slope compensation, and is devoid of the maximum duty cycle limitations which are prevalent in most constant frequency PWM controllers.
The HV9910B is a constant off time controller , but does not contain in internal error amplifier.
HV9910B datasheet:
https://www.electro-tech-online.com/custompdfs/2013/09/HV9910B.pdf