MP3275

6

Rev. 4.00

PRODUCT INFORMATION

Basic Description

The MP3275 is a fault protected data acquisition subsystem

available in monolithic form. This product contains all of the cir-

cuitry necessary to acquire 16 channels of quasi differential or

single-ended analog signals at

10 V input range and 15kHz

bandwidth. Connections to power, the analog input signals and

the digital system are all that is required. The MP3275’s input

circuitry is protected against active input signals present with the

MP3275 power off. This is also the case for any channel exceed-

ing the MP3275 analog input dynamic range without interfering

with the channel being digitized. The channel address and

channel conversion can be managed in two ways: random

channel conversion or same channel conversion. Circuitry on

the chip adds a MUX/instrumentation amp settling delay of 10

µs

max, when a new channel is selected (ADEN = 1). Conversion

start is initiated without delay for the single-channel case (ADEN

= 0). Data is available in serial format.

TIMING

Control and Timing Considerations

The MP3275 can be operated in the stand-alone mode, with

one line for control and everything else hard-wired; or under mi-

croprocessor control, where changes can be made dynamically.

There are 4 control lines: ADEN, WR, CS and RD with their

functions described in

Table 1.

Note 1: If RD = 1, SDO remain high impedance. It is recommended that RD will not change during a conversion in

order to reduce noise. It is further recommended that RD = 1 during conversion to reject any noise present on the

SDO.

Table 1. Logic Truth Table

CS

WR

RD

ADEN

Data

STL

STS

Comments

1

X

X

X

––

0

0

No operation

0

↓

1

0

Hi-Z

0

0

No operation if ADEN = 0

0

↓

1

1

Hi-Z

↑

0

Input MUX channel selected, STL set on WR falling edge

0

0

1

X

Hi-Z

1

0

MUX select disabled

0

↑

1

X

Hi-Z

0

↑

Start convert on WR rising edge

0

1

1

X

Hi-Z

↓↑

Start convert on STL falling edge

0

1

1

X

Hi-Z

0

↓

STS goes low at end of conversion

01

↓

X

––

0

0

SDO enabled

0

X

0

X

ADC

0

0

Data from previous conversion on SDO

0X

↑

X

Hi-Z

0

0

SDO disabled

0

1

X

X

Hi-Z

0

1

SDO/RD disabled while STS high

0

X

0

X

Last ADC

1

0

Data from last conversion on SDO

0

0

0

Hi-Z

0

↑

STL, MUX select disabled with ADEN = 0,

SDO disabled on STS rising edge

0

0

X

ADC

0

↓

New data appears on SDO on falling edge of STS

Read ADC Data

(See Figure 2. and Table 3.)

ADC Channel Select and Start Convert

(See Figure 1. and Table 2.)