Hi,
I am designing a adjustable current-feedback switching regulator for driving LED's. The switcher works at 500KHz, output is max. 3A dc at 6V dc. I want to monitor output average current for display. My logic (12-bit ADC) runs at 3.3V. Output current ripple is expected to be about 10mA p-p.
I was looking at the wide selection (86 chips!) of shunt monitors and I want to ask specifically about the LMV8640.
Looking at the datasheet I noticed:
Page 4 of the datasheet (2.7 V characteristics) says "Minimum output voltage = 80mV" for the 100V/V option. Is that with zero shunt current? I contrast this with Fig.15 on page 10, which shows a 25mV Vout for zero Vsense. What output will I get at 100mA if I use a 10 milliohm shunt? How about 50mA?
Also there is no mention of input filter. If I use one, will it degrade the accuracy, offset, output, if so by how much?
I would be grateful if anyone could explain the above, and perhaps suggest a way to measure switcher output current with tolerable accuracy (<5% error) solely for display purposes.
Bas