MCP2030 datasheet(46/66 Pages) MICROCHIP

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MCP2030

DS21981A-page 46

5.30.3.1

ANALOG-TO-DIGITAL DATA

CONVERSION OF RSSI SIGNAL

The RSSI output is an analog current. It needs an

external Analog-to-Digital (ADC) data conversion

device for digitized output. The ADC data conversion

can be accomplished by using a stand-alone external

ADC device, an external MCU that has internal ADC

features, or an external MCU that has no ADC features

but instead uses firmware. The RSSIFET is used to

discharge any external charge on the LFDATA pin in

the RSSI Output mode. The MOSFET can be turned on

or off with bit RSSIFET<8> of Configuration Register 2

(Register 5-3). When it is turned on, the internal

MOSFET provides a discharge path for the external

capacitor that is connected at the LFDATA pin. This

MOSFET option is valid only if RSSI output is selected

and not controllable by users for demodulated or carrier

clock output options.

See separate application notes for various external ADC

implementation methods for this device.

See Figure 5-8 for RSSI output path.

5.31

onfiguration Registers

5.31.1

SPI COMMUNICATION

The SPI communication is used to read from or write to

the Configuration registers and to send command-only

messages.

Three

pins

are

used

for

SPI

communication: CS, SCLK/ALERT, and LFDATA/RSSI/

CCLK/SDIO. Figure 5-9, Figure 5-10 and Figure 5-11

show examples of the SPI communication sequences.

When these pins are connected to the external MCU

I/O pins, the following are needed:

• Pin is permanently an input with an internal pull-up.

SCLK/ALERT

• Pin is an open collector output when CS is high.

An internal pull-up resistor exists to ensure no

spurious SPI communication between powering

and the MCU configuring its pins. This pin

becomes the SPI clock input when CS is low.

LFDATA/CCLK/SDIO

• Pin is a digital output (LFDATA) so long as CS is

high. During SPI communication, the pin is the

SPI data input (SDI) unless performing a register

Read, where it will be the SPI data output (SDO).

FIGURE 5-9:

Power-Up Sequence.

SCLK/ALERT

LFDATA/CCLK/SDIO

ALERT

LFDATA

(output)

(open collector

output)

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