I am looking at LT3652 datasheet, and I see the Battery Floating Voltage is set with a voltage divider between pins BAT and VFB. 2 equations are provided to calculate the resistor values (page 14, equations for Rfb1 and Rfb2). The 2 equations on page 14 are RFB1 = (VBAT(FLT) • 2.5 • 10^5)/3.3 and RFB2 = (RFB1 • (2.5 • 105))/(RFB1 - (2.5 • 10^5))
I am trying to use these equations to match the typical application example on page 26, where rfb1 is 309k and rfb2 is 100k, but I can't satisfy the 2 equations. The only thing I notice is that with a voltage of 13.5v applied to that voltage divider, output is 3.3v.
Could you please help me to clarify how these values relate to the equations provided?