MCP2036-ESLASHP datasheet(3/30 Pages) MICROCHIP

3 / 30 page

DS22186B-page 3

MCP2036

FIGURE 1-2:

MCP2036 Typical Application

The coil voltages are then multiplexed into the

Synchronous Detector section by the LBTN/LREF

multiplexer. This allows the microcontroller to select

which signal is sampled by the detector. The detector

converts the coil voltages into a DC level using a

frequency mixer, amplifier, and filter.

The mixer is composed of two switches driven by the

clock present on the CLK signal input. The switches

toggle the amplifier/filter between an inverting and

non-inverting topology, at a rate equal to the clock input

frequency. This inverts and amplifies the negative side

of the signal, while amplifying the positive side. The

result is a pulsed DC signal with a peak voltage,

proportional to the amplitude of the AC coil voltage.

The gain of the detector is set by two pairs of resistors;

one pair are the internal fixed series resistors between

the frequency mixer and the amplifier. The second

resistor pair are the two external gain set resistors

(RGAIN). The two capacitors (CFILTER) in parallel with

the external gain setting resistors form a low pass filter

which converts the pulsed DC output signal into a

smooth DC voltage which is proportional to the AC

sensor voltage input. The output of the system is

present on the VDETOUT pin, which drives the

microcontroller’s ADC input for conversion into a digital

value.

The virtual ground reference for the detector/amplifier

is generated by a second internal op amp which

produces a virtual ground equal to ½ the supply

voltage. The virtual ground is available externally at the

VREF output and used internally throughout the

detector circuit, allowing single supply operation. A

small external capacitance is required to stabilize this

output and limit noise.

MCP2036

LREF

LBTN

LREF

DRVOUT

10nF

REFSEL

10nF

I/O

CD4052

Key Coils

PIC® Microcontroller

I/O

VDET-

VDETOUT

VDET+

VREF

CLK

DRVIN

PWM

ADC

CFILTER

RGAIN

CRGND

RIN

CIN

RADC

CADC

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