Rainbow-electronics MAX5511 Manual de usuario descargar pdf (Pagina 16)

MAX5510/MAX5511

+1.8V to +5.5V, Ultra-Low-Power, 8-Bit,

Voltage-Output DACs

16 ______________________________________________________________________________________

Unipolar Output

Figure 7 shows the MAX5510 in a unipolar output con-

figuration with unity gain. Table 4 lists the unipolar out-

put codes.

Bipolar Output

The MAX5510 output can be configured for bipolar

operation, as shown in Figure 8. The output voltage is

given by the following equation:

OUT

= V

REF

x [(N

- 128) / 128]

where NA represents the numeric value of the DAC’s

binary input code. Table 5 shows digital codes (offset

binary) and the corresponding output voltage for the

circuit in Figure 4.

Configurable Output Gain

The MAX5510/MAX5511 have a force-sense output,

which provides a connection directly to the inverting ter-

minal of the output op amp, yielding the most flexibility.

The advantage of the force-sense output is that specific

gains can be set externally for a given application. The

gain error for the MAX5510/MAX5511 is specified in a

unity-gain configuration (op-amp output and inverting ter-

minals connected), and additional gain error results from

external resistor tolerances. Another advantage of the

force-sense DAC is that it allows many useful circuits to

be created with only a few simple external components.

Figure 8. Bipolar Output Circuit

DAC CONTENTS

MSB

LSB

ANALOG OUTPUT

1111

1111 0000

REF

(127/128)

1000

0001 0000

REF

(1/128)

1000

0000 0000

0111

1111 0000

-V

REF

(1/128)

0000

0001 0000

-V

REF

(127/128)

0000

0000 0000

-V

REF

(128/128) = -V

REF

Table 5. Bipolar Code Table (Gain = +1)

REFIN

MAX5510

OUT

V+

10kΩ 10kΩ

V-

DAC

BAND

GAP

TO ADC

OUT

REFOUT

MAX5511

TO ADC

SENSOR

REF

Figure 6. Self-Biased Two-Electrode Potentiostat Application

IS THE DAC INPUT CODE

(0 TO 255 DECIMAL).

REFIN

MAX5510

OUT

REFIN

× N

256

DAC

Figure 7. Unipolar Output Circuit

DAC CONTENTS

MSB

LSB

ANALOG OUTPUT

1111 1111 0000

REF

(255/256)

1000 0001 0000

REF

(129/256)

1000 0000 0000

REF

(128/256) = +V

REF

0111 1111 0000

REF

(127/256)

0000 0001 0000

REF

(1/256)

0000 0000 0000

Table 4. Unipolar Code Table (Gain = +1)

1 2 ... 11 12 13 14 15 16 17 18

MAX5510/MAX5511 1
Voltage-Output DACs 1

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