MCP3909T(2006) 데이터 시트보기 (PDF) - Microchip Technology

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MCP3909T
(Rev.:2006)

Energy Metering IC with SPI Interface and Active Power Pulse Output

Microchip Technology 

5.0 SERIAL INTERFACE

DESCRIPTION

5.1 Dual Functionality Pin And Serial

Interface Overview

The MCP3909 device contains three serial modes that

are accessible by changing the pin functionality of the

NEG, F2, F1, and F0 pins to SDO, SCK, SDI and CS,

respectively.

These modes are entered by giving the MCP3909

device a serial command on these pins during a time

window after device reset or POR. During this window

of time, F2 acts as SCK, F1 acts as SDI and F0 acts

as CS. Once a serial mode has been entered, the

device must be reset to disable mode functionality, or

change to another serial mode. This is done by using

MCLR pin or power on reset event.

During serial mode entry and the three serial modes,

data is clocked into the device on the rising edge of

SCK and out of the device on the falling edge of SCK.

The SPI data can be access at up to 20 MHz. This

speed enables quick data retrieval in between

conversion times. For 3-phase metering applications

MCP3909

with multiple ADCs, this fast communication is essen-

tial to allow for power calculation windows between

conversions, as shown in Figure 5-3.

After a serial mode has been entered, all blocks of the

MCP3909 device are still operational. The PGA, A/D

converters, HPF, multiplier, LPF, and other digital

sections are still functional, allowing the device to have

true dual functionality in energy metering systems.

DVDD 1

HPF 2

AVDD 3

NC 4

CH0+ 5

CHO- 6

CH1- 7

CH1+ 8

MCLR 9

REFIN / OUT 10

AGND 11

F2 / SCK 12

24 FOUT0

23 FOUT1

22 HFOUT

21 DGND

20 NEG / SDO

19 NC

18 CLKOUT

17 CLKIN

16 G0

15 G1

14 F0 / CS

13 F1 / SDI

FIGURE 5-1:

the MCP3909.

Dual Functionality Pins for

IRQ

tSAMPLE

tLINE_CYC

IRQ Phase A,B,C I & V Data

SDO DR

16 bits

x 6 ADCs

DR

tSAMPLE

FIGURE 5-2:

Data Access between Data Ready Pulses using SPI Interface for a 3-phase System.

© 2006 Microchip Technology Inc.

DS22025A-page 21

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