MAX5812 Просмотр технического описания (PDF) - Maxim Integrated

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MAX5812

12-Bit Low-Power, 2-Wire, Serial Voltage-Output DAC

Maxim Integrated 

12-Bit Low-Power, 2-Wire, Serial

Voltage-Output DAC

MSB

LSB

MSB

S

A6

A5

A4

A3

A2

A1

A0

R/W

=0

ACK

C3 C2 X

XX

LSB

X X X ACK

DATA BYTES GENERATED BY MASTER DEVICE

MSB

LSB

MSB

LSB

Sr

A6

A5

A4

A3

A2

A1

A0

R/W

=1

ACK

X X PD1 PD0 D11 D10 D9 D8 ACK

DATA BYTES GENERATED BY MAX5812

MSB

LSB

D7 D6 D5 D4 D3 D2 D1 D0 ACK

P

Figure 7. Example Read Word Data Sequence

ACK GENERATED BY

MASTER DEVICE

IN

OUT

MAX6030/

MAX6050

GND

VDD

MAX5812 OUT

GND

Figure 8. Powering the MAX5812 from An External Reference

Read Data Format

In read mode (R/W = 1), the MAX5812 writes the con-

tents of the DAC register to the bus. The direction of

data flow reverses after the address acknowledge by

the MAX5812. The device transmits the first byte of

data, waits for the master to acknowledge, and then

transmits the second byte. Figure 7 shows an example-

read data sequence.

I2C Compatibility

The MAX5812 is compatible with existing I2C systems.

SCL and SDA are high-impedance inputs; SDA has an

open drain that pulls the data line low during the ninth

clock pulse. The Typical Operating Circuit shows a typ-

ical I2C application. The communication protocol sup-

ports standard I2C 8-bit communications. The general

call address is ignored. The MAX5812 address is com-

patible only with the 7-bit I2C addressing protocol. Ten-

bit address formats are not supported.

Digital Feedthrough Suppression

When the MAX5812 detects an address mismatch, the

serial interface disconnects the SCL signal from the

core circuitry. This minimizes digital feedthrough

caused by the SCL signal on a static output. The serial

interface reconnects the SCL signal when a valid

START condition is detected.

Applications Information

Powering the Device From an

External Reference

The MAX5812 uses the VDD as the DAC voltage refer-

ence. Any power-supply noise is directly coupled to the

device output. The circuit in Figure 8 uses a precision

voltage reference to power the MAX5812, isolating the

device from any power-supply noise. Powering the

MAX5812 in such a manner greatly improves overall

performance, especially in noisy systems. The

MAX6030 (3V, 75ppm/°C) or the MAX6050 (5V,

75ppm/°C) precision voltage references are ideal

choices because of the low power requirements of the

MAX5812.

Digital Inputs and Interface Logic

The MAX5812 2-wire digital interface is I2C and SMBus-

compatible. The two digital inputs (SCL and SDA) load

______________________________________________________________________________________ 11

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