ADA4807-2ACPZ-R2 datasheet(29/33 Pages) AD

29 / 33 page

Data Sheet

ADA4807-1/ADA4807-2/ADA4807-4

Rev. B | Page 29 of 33

ADC DRIVING WITH DYNAMIC POWER SCALING

In power sensitive applications, the ADA4807-1/ADA4807-2

can be switched on prior to the ADC turning on. Figure 78

shows the timing diagram for dynamically power scaling the

ADA4807-1/ADA4807-2 with the AD7982 configuration shown in

Figure 79. The falling edge of the DISABLE signal must align

with the rising edge of the CONV signal of the ADC to obtain a

clean data acquisition. Figure 79 gives the FFT for driving a fully

differential signal chain with a 1.2 µs on time as shown in Figure 78.

With this method, the ADA4807-1/ADA4807-2 quiescent current

(per amplifier) is reduced from 2 mA to 0.25 mA. Figure 81 gives

the FFT for dynamically power scaling a single-ended input

signal chain into a differential ADC with a 4 µs on time as

shown in Figure 80. This configuration results in a quiescent

current reduction of 20%.

CH1 2V

CH2 2V

M1µs

A CH1

2.56V

CONV

DISABLE

Figure 78. Dynamic Power Scaling Timing Diagram for Driving a Fully

Differential Signal Chain into a Differential ADC (AD7982)

–20

–40

–60

–80

–100

–120

–140

–160

–180

FREQUENCY (kHz)

fs = 200kSPS

fIN = 1kHz

SNR = 96.7dB

THD = –110.9dB

SFDR = –111.8dB

SINAD = 96.6dB

Figure 79. FFT for Driving a Differential Converter using Dynamic Power Scaling,

−0.5 dBFS, On Time of 1.2 µs, for the Schematic Shown in Figure 74

CH1 2V

CH2 2V

M1µs

A CH1

2.56V

CONV

DISABLE

Figure 80. Dynamic Power Scaling Timing Diagram for Driving a Single-

Ended Input Signal Chain into a Differential ADC (AD7982)

–20

–40

–60

–80

–100

–120

–140

–160

–180

FREQUENCY (kHz)

fs = 200kSPS

fIN = 1kHz

SNR = 94.7dB

THD = –107.11dB

SFDR = –108.8dB

SINAD = 94.4dB

Figure 81. FFT for Driving a Single-Ended to Differential Converter Using

Dynamic Power Scaling, −0.5 dBFS, On Time of 4 µs, for the Schematic Shown in

Figure 76

ADA4807-2ACPZ-R2 数据表(PDF) 29 Page - Analog Devices

ADA4807-2ACPZ-R2 数据表(HTML) 29 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

数据表下载