MCP19124 datasheet(48/236 Pages) MICROCHIP

48 / 236 page

MCP19124/5

DS20005619A-page 48

 2016 Microchip Technology Inc.

6.9

Current Regulation Reference

Configuration

The VREFCON register controls the error amplifier

reference voltage. This reference is used to set the

current regulation set point. VREFCON holds the digital

value used by an 8-bit linear DAC setting the analog

equivalent that gets summed with the pedestal voltage

(VZC) at the noninverting node of the current error

amplifier (EA1). VZC is equal to the band gap voltage

(1.23V). The output of the current sense amplifier A2 is

also raised on the pedestal voltage, effectively

canceling its effect on the input. The pedestal is

implemented throughout the analog current control

loop to improve accuracy at low levels. The VREF DAC

can be adjusted in 255 steps of 4.8 mV/step.

Whichever error amplifier (EA1 or EA2) has the lower

output signal takes control of the PWM control loop.

VREFCON: CURRENT/VOLTAGE REGULATION SET POINT CONTROL

R/W-0

VREF7

VREF6

VREF5

VREF4

VREF3

VREF2

VREF1

VREF0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

u = Bit is unchanged

x = Bit is unknown

-n = Value at POR

‘1’

= Bit is set

‘0’

= Bit is cleared

bit 7-0

VREF<7:0>: Voltage-Controlling Current Regulation Set Point bits

VREF(V) = VBG x N/255 where N = the decimal value written to the VREFCON Register VREF<7:0>

from 0 to 255.

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