Rainbow-electronics MAX5159 Manual do Utilizador descarregar pdf (Página 14)

MAX5158/MAX5159

produce a range of 0V to 2.5V with a 1.25V reference.

Table 2 lists the unipolar output codes. An offset to the

output can be achieved by connecting a voltage to

OS_, as shown in Figure 10. By applying V

_ = -1V,

the output values will range between 1V and (1V +

REF

x 2).

Bipolar Output

The MAX5158/MAX5159 can be configured for a bipo-

lar output, as shown in Figure 11. The output voltage is

given by the equation (OS_ = AGND):

OUT

= V

REF

[((2 x NB) / 1024) - 1]

where NB represents the numeric value of the DAC’s

binary input code. Table 3 shows digital codes and the

corresponding output voltage for Figure 11’s circuit.

Using an AC Reference

In applications where the reference has an AC signal

component, the MAX5158/MAX5159 have multiplying

capabilities within the reference input voltage range

specifications. Figure 12 shows a technique for apply-

ing a sinusoidal input to REF_, where the AC signal is

offset before being applied to the reference input.

Harmonic Distortion and Noise

The total harmonic distortion plus noise (THD+N) is typ-

ically less than -78dB at full scale with a 1Vp-p input

swing at 5kHz. The typical -3dB frequency is 300kHz

for both devices, as shown in the

Typical Operating

Characteristics.

Low-Power, Dual, 10-Bit Voltage-Output DACs

with Serial Interface

14 ______________________________________________________________________________________

Table 3. Bipolar Code Table

ANALOG OUTPUT

11 1111 1111 (000)

10 0000 0001 (000)

DAC CONTENTS

MSB LSB

10 0000 0000 (000) 0V

01 1111 1111 (000)

00 0000 0000 (000)

00 0000 0001 (000)

511

512

REF













512

REF













-V

512

REF













-V

511

512

REF













-V

512

- V

REF REF













AGNDDGND

MAX5158

MAX5159

DAC _

REF_

OS_

OUT_

10k 10k

10k

V-

V+

OUT

+5V/+3V

Figure 11. Bipolar Output Circuit

DAC_

OUT_

MAX5158

MAX5159

10k

26k

OS_

REF

DGNDAGND

+5V/

+3V

REFERENCE

INPUT

500mVp-p

MAX495

+5V/+3V

Figure 12. AC Reference Input Circuit

AGND

DIN

µP

DGND

MAX5158

MAX5159

DAC _

REF_

OS_

OUT_

V-

V+

PHOTODIODE

V+

OUT

PULLDOWN

+5V/+3V

Figure 13. Digital Calibration

Note: ( ) are for the sub bits.

1 2 ... 9 10 11 12 13 14 15 16

MAX5158/MAX5159 1

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