LT3932 minimum current when use CTRL pin

Hi phamtrieu138,

Based on page 14 of the datasheet, the LED current can go to zero for duty cycle of less than 12.5%. I think 5mA can be achieved.

1. with output current = 1.2A max, Rsense = 0.082 ohm.

2. with Rsense = 0.082 ohm, Ioutmin = 5mA, Isp-Isn = 0.41 mV.  This voltage is more than offset voltage of a lot of amplifiers. In datasheet, i don't see the offset voltage of inside amplifier of output current sense module. so, could you tell me this parameter?

Hi phamtrieu138,

I consulted with product expert and I would like to correct my answer. This is not exactly possible (at least with a single LED driver). The offset voltage for the current sense amplifier becomes an issue at that low of a differential sense voltage. For an application like this that requires such a wide range of analog dimming, you would need two LED drivers to perform this function with any sort of accuracy. It would allow for a bit better optimization of the lower current level accuracy but requires a bit of control logic to send the analog dimming signals to each converter and have smooth transitions between coarse and fine adjustments. 

Hi phamtrieu138,

I consulted with product expert and I would like to correct my answer. This is not exactly possible (at least with a single LED driver). The offset voltage for the current sense amplifier becomes an issue at that low of a differential sense voltage. For an application like this that requires such a wide range of analog dimming, you would need two LED drivers to perform this function with any sort of accuracy. It would allow for a bit better optimization of the lower current level accuracy but requires a bit of control logic to send the analog dimming signals to each converter and have smooth transitions between coarse and fine adjustments. 

thanks for your reply.

With this requirement (continuous current from 5 to 1200mA), could you recommend for me another LED driver that only use 1 driver for 1 LED?