Just one simple Q about LT3476 VREF pin, can i connect it to a digital potentiometer directly for dimming tuning instead of resistor string? Thank you so much.
The Electrical Characteristics table in the LT3476 datasheet indicates that REF is characterized up to 200uA, so it should be o.k. to load REF with a digital potentiometer as you mention, especially if the current is around 200uA and below. I show the REF line item from the LT3476 datasheet EC table in the image below:
Good day, just want to confirm, can Vref be float or only bypass to GND through capacitor? We will use four channel digital potentiometer to replace the resistor strings, but seems Vref can not drive this potentiometer if four channels work in the same time, we will use external 1.05v to replace VREF.
I'm sure it is o.k. to float REF but I would bypass REF with a 0.1uF capacitor because that is the recommendation in the Pin Functions section of the LT3476 datasheet. I show the text in the image below:
The LT3476 REF current is characterized up to 200uA - not 10uA as I said in my original REPLY post. I went back and fixed my original REPLY post to say 200uA instead of 10uA.
I can't explain why the REF bypass capacitor used by demonstration circuit DC976A is only 22nF as shown by the DC976A schematic portion in your post.