LT1028 datasheet(19/28 Pages) AD

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LTC6226/LTC6227

Rev 0

For more information www.analog.com

TYPICAL APPLICATIONS

16-Bit High Performance Transparent ADC Driver

The ultralow noise and distortion performance of the

LTC6226/LTC6227 makes it an excellent candidate for

driving high sample rate high resolution ADCs. Figure 4

shows the LTC6227 driven by a differential input, driving

an AD7380, a 4Msps, 16-bit ADC. Figure 5 shows the FFT

obtained with a –0.5 dBFS, 50kHz input signal. Spurious

free dynamic range is an excellent 108.5dB with an SNR

of 91dB. Increasing the input frequency to 100kHz results

in excellent performance as well, with a THD of –100dBc,

SNR of 89dB and SFDR of 104.9dB.

High Performance Single Ended to Differential 16-Bit

ADC Driver

In many applications, the signal to be digitized is single

ended, whereas the A/D Converter needs differential inputs

to maximize performance. The LTC6227 can be used to

implement a Single-Ended to differential ADC driver as

shown in Figure 6. One channel is configured in unity gain

and drives another channel configured in an inverting gain

stage of 1, both outputs drive the LTC2323-16 through an

RC filter. Figure 7 shows the FFT obtained with a –1dBFS

156.25kHz input signal, with a demanding 5Msps sample

rate. The obtained SNR of 81 dB is equivalent to that of

the ADC by itself, thus there is no degradation due to the

driver. The SFDR obtained is 84dB.

62267 F04

–

330pF

3.3V

ADR4533

2.5V

2.2µF

1/2 LTC6227

68pF

3.3V

68pF

–

1/2 LTC6227

–2.5V

3.3V

AD7380

IN–

IN+ VCC VREF VLOGIC

Figure 4. Transparent Driver for 16-Bit ADC

Figure 5. Measured Performance of LTC6227

Based Driver Driving the AD7380

6.23VP–P 50kHz INPUT SIGNAL

FREQUENCY (kHz)

400

800

1200

1600

2000

–180

–160

–140

–120

–100

–80

–60

–40

–20

62267 F05

SNR = 91 dB

THD = –104.8 dB

SFDR = 108.5 dB

16-Bit ADC Driver Performance

Input Signal = –0.5dBFS

fSMPL = 4Msps, fIN = 50kHz

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