MCP33131 datasheet(38/54 Pages) MICROCHIP

38 / 54 page

DS20006122A-page 38

 2018 Microchip Technology Inc.

MCP33131/MCP33121/MCP33111-XX

7.0

DIGITAL SERIAL INTERFACE

The device has a SPI-compatible serial digital

interface using four digital pins: CNVST, SDI, SDO and

SCLK.

Figure 7-1 shows the connection diagram with the host

device and Figure 7-2 shows the SPI-compatible serial

interface timing diagram.

The SDI pin can be tied to the digital I/O interface

supply voltage (DVIO) or just maintain logic “High” level

by the host. The CNVST pin is used for both chip select

(CS) and conversion-start control.

A rising edge on CNVST initiates the conversion

process. Once the conversion is initiated, the device

will complete the conversion regardless of the state of

CNVST. This means the CNVST pin can be used for

other purposes during tCNV.

When the conversion is complete, the output is

available at SDO by lowering CNVST. Data is sent

MSB-first and changes on the falling edge of SCLK.

Output data can be sampled on either edge of SCLK.

However, a digital host capturing data on the falling

edge of SCLK can achieve a faster read out rate.

SDO returns to high-Z state after the last data bit is

clocked out or when CNVST goes high, whichever

occurs first.

FIGURE 7-1:

Digital Interface Connection

Diagram.

FIGURE 7-2:

SPI Compatible Serial Interface Timing Diagram (16-bit device).

CNVST

SCLK

SDO

SCLK

SDI

(a) MCP33131/21/11-XX

(b) Host Device (Master)

Note 1: Adding this pull-up is needed when monitoring

status of Recalibrate.

DVIO

(Note 1)

10 k



SDI

DVIO

CNVST

SDO

SCLK

D15

D14

D13

D12

ADC State

(MSB)

Hi-Z

tCNVH

tCNV (MAX)

tSCLK

tSCLK_L tSCLK_H

tDO

tDIS

Conversion

(a) Exit input acquisition mode and

(b) Enter new conversion mode

Note 1: SDI must maintain “High” during the entire

tCYC.

(Note 2)

Input Acquisition

(tCNV)

(tACQ)

tCYC

2: Any SCLK toggling events (dummy clocks) before CNVST is changed to “Low” are ignored.

SDI = DVIO

tSU_SDIH_CNV

(Note 1)

tEN

tQUIET

tEN

(Note 3)

(Note 4)

3: tEN when CNVST is lowered after tCNV (Max).

4: tEN when CNVST is lowered before tCNV (Max).

= 1/fS

(Note 5)

5: Recommended data detection: Detect SDO on the falling edge of SCLK.

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