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LTC6373

Rev. 0

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Table 5. SNR and THD Results for LTC6373 Directly Driving AD7134 (at 250ksps)

ADC

LTC6373 Gain

Setting (G)

VREF

(V)

Signal Level at LTC6373

Outputs = ADC Inputs (VP-P)

(Ω)

CCM

(pF)

CDIFF

(pF)

fIN (kHz) Typical

SNR (dB)

Typical

THD (dB)

AD7134

0.25

4.096

8.192

0 Open Open

108.4

–124

107.7

–97

4.096

8.192

0 Open Open

107.2

–121

106.9

–100

4.096

8.192

0 Open Open

94.3

–112

94.3

–93

Table 6. Details for LTC6373 Driving ADAQ4003 at 3 Different Gain Options and Signal Amplitudes

ADAQ4003

Gain

VREF

(V)

Signal Level at LTC6373

Outputs = ADAQ4003 Inputs (VP-P)

Circuit Configuration

Typical SNR

(dB)

Typical THD

(dB)

0.454

See Figure 11

See Figure 12

See Figure 13

0.9

See Figure 14

See Figure 15

See Figure 16

1.9

5.2

See Figure 17

See Figure 18

See Figure 19

Table 5 lists the typical SNR and THD achieved when the

ADC used in Figure 8 is AD7134 ∑-∆ ADC being driven

directly (with no RC filter in between) by the LTC6373 at

a near full-scale signal.

In some applications, it might be beneficial to use a

separate amplifier/ADC driver between the LTC6373 and

the precision ADC to ease the settling requirements on

the LTC6373 and improve the linearity and THD perfor-

mance of the signal chain. An implementation of such

signal chain can be achieved by using the ADAQ4003,

a precision data acquisition µModule which integrates

multiple signal conditioning and processing blocks inside

a single package. These blocks include a fully differential

ADC driver, a stable reference buffer, an 18-bit, 2Msps,

SAR ADC, as well as critical passive components neces-

sary for optimum performance. This µModule achieves 4X

footprint reduction by itself (compared to discrete solu-

tion) without sacrificing any performance.

The ADAQ4003 offers pin-selectable gain or attenuation

options, giving the user the flexibility to match to their

input signal range. This is showcased in Figures 11-19

as LTC6373 is directly driving the ADAQ4003 at its 3

different gain options, in each case providing the signal

amplitude necessary to utilize the maximum 2VREF peak-

to-peak differential signal range of the ADC inside the

ADAQ4003 µModule.

APPLICATIONS INFORMATION

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