LTC2602 datasheet(20/32 Pages) LINER

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LTC2320-12

Rev B

For more information www.analog.com

APPLICATIONS INFORMATION

generated by the ADC and must be clamped by the user,

if necessary.

Single-Ended-to-Differential Conversion

While single-ended signals can be directly digitized as pre-

viously discussed, single-ended to differential conversion

circuits may also be used when higher dynamic range is

desired. By producing a differential signal at the inputs of

the LTC2320-12, the signal swing presented to the ADC is

maximized, thus increasing the achievable SNR.

The LT®1819 high speed dual operational amplifier is

recommendedforperformingsingle-ended-to-differential

conversions, as shown in Figure 8. In this case, the first

amplifier is configured as a unity-gain buffer and the

single-ended input signal directly drives the high imped-

ance input of this amplifier.

Figure 8. Single-Ended to Differential Driver

VREF

VREF/2

–

200

LT1819

232012 F08

Fully-Differential Inputs

To achieve the best distortion performance of the

LTC2320-12, we recommend driving a fully-differential

signal through LT1819 amplifiers configured as two

unity-gain buffers, as shown in Figure 9. This circuit

achieves the full data sheet THD specification of –90dB at

input frequencies up to 500kHz. A fully-differential input

signal can span the maximum full-scale of the ADC, up to

±REFOUT1,2,3,4. The common mode input voltage can

span the entire supply range up to VDD, limited by the

input signal swing. The fully-differential configuration is

illustrated in Figure 10, with the corresponding transfer

function illustrated in Figure 11.

220pF

VREF

ONLY CHANNEL 1 SHOWN FOR CLARITY

–

LTC2320-12

LT1819

232012 F10

SDO1

REF

REFOUT1

CLKOUT

AIN1–

AIN1+

SCK

TO CONTROL

LOGIC

(FPGA, CPLD,

DSP, ETC.)

1µF

10µF

Figure 9. LT1819 Buffering a Fully-Differential Signal Source

VREF

–

LT1819

232012 F09

Figure 10. Fully-Differential Application Circuit

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