MCP3464T-ESLASHST datasheet(48/108 Pages) MICROCHIP

48 / 108 page

MCP3461/2/4

DS20006180D-page 48

 2019-2021 Microchip Technology Inc.

FIGURE 5-10:

ADC Start-up Timer Timing Diagram.

5.11

Master Clock Selection/Internal

Oscillator

The device includes three possible clock modes for the

master clock generation. The Master Clock (MCLK) is

used by the ADC to perform conversions and is also

used by the digital portion to generate the different digital

timers. The clock mode selection is made through the

CLK_SEL[1:0] bits located in the CONFIG0 register. The

possible selections are described in Table 5-12.

The master clock is not propagated in the chip when

the chip is placed into the Full Shutdown mode (see

Section 5.9 “Low-Power Shutdown Modes”). Any

change to the CLK_SEL bits creates a Reset and

restart for the currently running conversions, and a

restart of the ADC setup timer. Each Reset and restart

will reset all internal phases to their default values and

can lead to a possible temporary duty cycle change at

the clock output pin.

5.11.1

EXTERNAL MASTER CLOCK MODE

(CLK_SEL[1:0] = 0x)

The External Clock mode is used to input the MCLK

clock necessary for the ADC conversions and can

accept duty cycles with a large range since the clock is

redivided internally to generate the different internal

phases.

The external clock can be provided on the MCLK pin for

the MCP3461/2/4 devices.

5.11.2

INTERNAL OSCILLATOR

The device includes an internal RC-type oscillator

frequency of this internal oscillator ranges from 3.3 to

6.6 MHz. The oscillator is not trimmed in production,

therefore, the precision of the center frequency is

approximately ±30% from chip-to-chip. The duty cycle

of the internal oscillator is centered around 50% and

varies very slightly from chip-to-chip. The internal

oscillator has no Reset feature and keeps running once

selected.

ADC Start-up

Timer Decimal

Code

ADC_MODE

DMCLK

256

Continuous Clocking

Switching Between ADC_MODE =

10 and 11

has no Effect on the Timer

Timer Reset

ADC Ready to Convert

SPI

Wri te

AD C_MODE =

Wri te

AD C_MODE =

Wri te

AD C_MODE =

Wri te

AD C_MODE =

Timer Reset

Timer

Countdown

TABLE 5-12:

CLOCK SELECTION BITS

CLK_SEL[1:0]

Clock Mode

MCLK Pin

00 or 01

External clock

MCLK digital input

Internal RC

Oscillator, no

clock output

High-Z

Internal RC

Oscillator with

clock output

AMCLK digital

output

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