MAX519ACSE データシートの表示（PDF） - Maxim Integrated

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MAX519ACSE

2-Wire Serial 8-Bit DACs with Rail-to-Rail Outputs

Maxim Integrated 

2-Wire Serial 8-Bit DACs with

Rail-to-Rail Outputs

11

(a)

or or

(RST) (PD)

0 1 0 AD3 AD2 AD1 AD0 0 0 0 0 0 1 1 0

SDA

START

CONDITION

ADDRESS BYTE

ACK INTERRUPTED

( ) COMMAND BYTE EARLY

MAX517/MAX518/MAX519's

STOP CONDITION STATE REMAINS UNCHANGED.

11

(b)

or or

(PD)

0 1 0 AD3 AD2 AD1 AD0 0 0 0 0 0 RST 1 0 0 0 0 1 1 1 0 0

SDA

XX

START

CONDITION

ADDRESS BYTE

ACK

COMMAND BYTE

(POWER DOWN)

ACK INTERRUPTED

OUTPUT BYTE

EARLY

( MAX517/MAX518/MAX519

POWER DOWN; INPUT LATCH

UNCHANGED IF RST = 0,

)

STOP CONDITION DAC OUTPUT(S) RESET IF RST = 1.

Figure 14. Early STOP Conditions

Table 1. Unipolar Code Table

DAC CONTENTS

11111111

10000001

10000000

01111111

00000001

00000000

ANALOG OUTPUT

( ) 255

+ VREF

———

256

( ) 129

+ VREF

———

256

( ) + VREF

128

———

256

= V—RE—F

2

( ) 127

+ VREF

———

256

+

VREF

(——1 —)

256

0V

age, both DC and AC signals. The voltage at each REF

input sets the full-scale output voltage for its respective

DAC. The reference voltage must be positive. The

DAC’s input impedance is code dependent, with the

lowest value occurring when the input code is 55 hex or

0101 0101, and the maximum value occurring when the

input code is 00 hex. Since the REF input resistance

(RIN) is code dependent, it must be driven by a circuit

with low output impedance (no more than RIN ÷ 2000)

to maintain output linearity. The REF input capacitance

is also code dependent, with the maximum value

occurring at code FF hex (typically 30pF). The output

voltage for any DAC can be represented by a digitally

programmable voltage source as: VOUT = (N x VREF) /

256, where N is the numerical value of the DAC’s binary

input code.

R

2R 2R

D0

R

R

OUT_

2R

2R

2R

D5

D6

D7

REF_*

GND

SHOWN FOR ALL 1s ON DAC

*REF = VDD FOR THE MAX518

Figure 15. DAC Simplified Circuit Diagram

Output Buffer Amplifiers

The DAC voltage outputs are internally buffered preci-

sion unity-gain followers that slew up to 1V/µs. The out-

puts can swing from 0V to VDD. With a 0V to 4V (or 4V

to 0V) output transition, the amplifier outputs typically

settle to 1/2LSB in 6µs when loaded with 10kΩ in paral-

lel with 100pF. The buffer amplifiers are stable with any

combination of resistive loads ≥2kΩ and capacitive

loads ≤300pF.

The MAX517/MAX518/MAX519 are designed for unipo-

lar-output, single-quadrant multiplication where the out-

put voltages and the reference inputs are positive with

respect to AGND. Table 1 shows the unipolar code.

______________________________________________________________________________________ 13

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