MCP2030 datasheet(28/66 Pages) MICROCHIP

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MCP2030

DS21981A-page 28

4.2

Application Examples

Figure 4-2 shows an example of an external circuit for

a bidirectional communication transponder application.

Each LC input pin is connected to an external LC

resonant circuit. To achieve the best performance, the

resonant frequency of the LC circuit needs to be

matched to the detecting carrier frequency of interest.

The resonant frequency is given by the following

equation:

In typical 125 kHz applications, the L value is a few mH,

and the C value is a few hundred pF, for example,

L = 4.9 mH, and C = 331 pF.

The resonant frequency can be fine-tuned by program-

ming the internal tuning capacitors.

The output of the MCP2030 is fed into the external

MCU. The external MCU can send data by clamping on

and clamping off the MCP2030 coil voltages using an

SPI command, or via a UHF transmitter.

The RSSI output of the MCP2030 can be digitized by

the MCU firmware. Users can also consider using a

MCU that has an internal analog-to-digital converter

(ADC) such as the PIC16F684 or a stand-alone ADC

device.

Figure 4-3 shows an example of a hands-free Passive

Keyless Entry (PKE) system. The base station unit

transmits an LF command. The MCP2030 detects the

base station command and feeds the detected output

to the external MCU (PIC16F636). If the command is

correct, the MCU responds via an external UHF

transmitter or by using the LF talk-back modulators of

the MCP2030 device.

Figure 4-4 shows an example when the device is used

for a tire pressure monitoring sensor application. The

device detects the LF Initiator commands and transmits

the tire pressure data to the base station via an external

UHF transmitter.

FIGURE 4-2:

Example of External Circuits for Bidirectional Communication Transponder Applications.

π LC

------------------

LCCOM

LCX

VSS

LFDATA/CCLK/SDIO

VDD

LCZ

LCY

VSS

SCLK/ALERT

RSSI

VDD

PIC16F636/684

To ADC

+3V

air-core

coil

ferrite-core

coil

ferrite-core coil

MCP2030

+3V

RF Circuitry

(UHF TX)

315/434 MHz

SW1

SW2

SW3

SW4

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