Rainbow-electronics MAX19515 Bedienungsanleitung PDF herunterladen (Seite 31)

MAX19515

Dual-Channel, 10-Bit, 65Msps ADC

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Applications Information

Analog Inputs

Transformer-Coupled Differential Analog Input

The MAX19515 provides better SFDR and THD with

fully differential input signals than a single-ended input

drive. In differential input mode, even-order harmonics

are lower as both inputs are balanced, and each of the

ADC inputs only require half the signal swing compared

to single-ended input mode.

An RF transformer (Figure 18) provides an excellent

solution for converting a single-ended signal to a fully

differential signal. Connecting the center tap of the

transformer to CM_ provides a common-mode voltage.

The transformer shown has an impedance ratio of 1:1.4.

Alternatively, a different step-up transformer can be

selected to reduce the drive requirements. A reduced

signal swing from the input driver can also improve the

overall distortion. The configuration of Figure 18 is good

for frequencies up to Nyquist (f

CLK

/2).

Figure 17. Integrated Voltage Regulator

2.3V TO 3.5V

ENABLE

OUT

1.8V

REGULATOR

REFERENCE

INTERNAL

ANALOG

CIRCUITS

AVDD

(PINS 1, 12, 13, 48)

GND

Figure 19. Transformer-Coupled Input Drive for Input Frequencies Beyond Nyquist

N.C.

0.1μF

MINI-CIRCUITS

ADT1-1WT

IN_+

CM_

IN_-

N.C.

MINI-CIRCUITS

ADT1-1WT

N.C.

75Ω

0.5%

75Ω

0.5%

110Ω

0.5%

110Ω

0.5%

0.1μF

MAX19515

Figure 18. Transformer-Coupled Input Drive for Input

Frequencies Up to Nyquist

MAX19515

N.C. N.C.

0.1μF

MINI-CIRCUITS

ADT1-1WT

36.5Ω

0.5%

36.5Ω

0.5%

0.1μF

IN_+

CM_

IN_-

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MAX19515 1

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