MAX1448 查看數據表（PDF） - Maxim Integrated

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MAX1448

10-Bit, 80Msps, Single 3.0V, Low-Power ADC with Internal Reference

Maxim Integrated 

10-Bit, 80Msps, Single 3.0V, Low-Power

ADC with Internal Reference

3.3V

0.1µF

1

MAX6066

3

2 21.5kΩ

2.0V

3

4

21.5kΩ

1

1/4 MAX4252

2

11

1µF

1.5V

3.3V

0.1µF

21.5kΩ

5

4

7

1/4 MAX4252

6

11

MAX4254 POWER-SUPPLY BYPASSING.

PLACE CAPACITOR AS CLOSE AS

POSSIBLE TO THE OP AMP.

1.0V

21.5kΩ

10

4

8

1/4 MAX4252

9

11

21.5kΩ

3.3V

2.0V AT 8mA

47Ω

10µF

6V

1.47kΩ

330µF

6V

3.3V

1.5V AT 0mA

47Ω

10µF

6V

1.47kΩ

330µF

6V

3.3V

1.0V AT -8mA

47Ω

10µF

6V

1.47kΩ

330µF

6V

0.1µF

N.C. 29 REFOUT

31 REFIN

32 REFP MAX1448

1 REFN N = 1

2 COM

0.1µF 0.1µF

0.1µF

0.1µF

N.C.

0.1µF

29 REFOUT

31 REFIN

32 REFP MAX1448

1 REFN N = 32

2 COM

0.1µF

2.2µF

10V

NOTE: ONE FRONT-END REFERENCE CIRCUIT DESIGN MAY BE USED WITH UP TO 32 ADCs.

Figure 11. Unbuffered External Reference Drives Up to 32 ADCs

Unbuffered External Reference

Drives Multiple ADCs

Connecting each REFIN to analog ground disables the

internal reference of each device, allowing the internal

reference ladders to be driven directly by a set of exter-

nal reference sources. Followed by a 10Hz lowpass fil-

ter and precision voltage-divider (Figure 11), the

MAX6066 generates a DC level of 2.500V. The buffered

outputs of this divider are set to 2.0V, 1.5V, and 1.0V,

with an accuracy that depends on the tolerance of the

divider resistors. The three voltages are buffered by the

MAX4252, which provides low noise and low DC offset.

The individual voltage followers are connected to 10Hz

lowpass filters, which filter both the reference voltage

and amplifier noise to a level of 3nV/√Hz. The 2.0V and

1.0V reference voltages set the differential full-scale

range of the associated ADCs at 2VP-P. The 2.0V and

1.0V buffers drive the ADC’s internal ladder resistances

between them. Note that the common power supply for

all active components removes any concern regarding

power-supply sequencing when powering up or down.

With the outputs of the MAX4252 matching better than

0.1%, the buffers and subsequent lowpass filters can

be replicated to support as many as 32 ADCs. For

applications that require more than 32 matched ADCs,

a voltage reference and divider string common to all

converters is highly recommended.

______________________________________________________________________________________ 17

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