2-Wire Serial 8-Bit DACs with

Rail-to-Rail Outputs

_______________________________________________________________________________________

7

Figure 1. MAX517/MAX519 Functional Diagram

_______________Detailed Description

Serial Interface

The MAX517/MAX518/MAX519 use a simple 2-wire

serial interface requiring only two I/O lines (2-wire bus)

of a standard microprocessor (µP) port. Figure 2 shows

the timing diagram for signals on the 2-wire bus.

Figure 3 shows a typical application. The 2-wire bus can

have several devices (in addition to the MAX517/

MAX518/MAX519) attached. The two bus lines (SDA and

SCL) must be high when the bus is not in use. When in

use, the port bits are toggled to generate the appropriate

signals for SDA and SCL. External pull-up resistors are

not required on these lines. The MAX517/MAX518/

MAX519 can be used in applications where pull-up resis-

compatibility with existing circuitry.

The MAX517/MAX518/MAX519 are receive-only devices

and must be controlled by a bus master device. They

operate at SCL rates up to 400kHz. A master device

sends information to the devices by transmitting their

address over the bus and then transmitting the desired

information. Each transmission consists of a START

condition, the MAX517/MAX518/MAX519’s programm-

able slave-address, one or more command-byte/out-

put-byte pairs (or a command byte alone, if it is the last

byte in the transmission), and finally, a STOP condition

(Figure 4).

______________________________________________________________Pin Description

PIN

MAX517

MAX518

MAX519

NAME

FUNCTION

1

1

1

OUT0

DAC0 Voltage Output

2

2

4

GND

Ground

—

—

5

AD3

Address Input 3; sets IC’s slave address

3

3

6

SCL

Serial Clock Input

4

4

8

SDA

Serial Data Input

—

—

9

AD2

Address Input 2; sets IC’s slave address

5

5

10

AD1

Address Input 1; sets IC’s slave address

6

6

11

AD0

Address Input 0; sets IC’s slave address

7

7

12

VDD

Power Supply, +5V; used as reference for MAX518

—

—

13

REF1

Reference Voltage Input for DAC1

8

—

15

REF0

Reference Voltage Input for DAC0

—

8

16

OUT1

DAC1 Voltage Output

—

—

2, 3, 7, 14

N.C.

No Connect—not internally connected.

INPUT

LATCH 0

OUTPUT

LATCH 0

START/STOP

DETECTOR

DAC0

INPUT

LATCH 1

8-BIT

SHIFT

REGISTER

OUT0

REF0

(REF1)

(OUT1)

MAX517/MAX519

DECODE

ADDRESS

COMPARATOR

DAC1

OUTPUT

LATCH 1

SCL

SDA

AD0

(AD2)

AD1

(AD3)

GND

MAX519 ONLY

( ) ARE FOR MAX519