ADA4805-1/ADA4805-2

Data Sheet

Rev. B | Page 22 of 25

SAMPLING FREQUENCY = 100kHz

ACQUISITION

ACQUISITION

ACQUISITION

SHUTDOWN

3µs

3µs

POWERED

ON

POWERED

ON

POWERED

ON

SHUTDOWN

SHUTDOWN

ADC

MODE

CNV

ADA4805-1/

ADA4805-2

SHUTDOWN

CONVERSION

CONVERSION

CONVERSION

MINIMUM

POWERED ON TIME = 3µs

ADA4805-1/

ADA4805-2

OUTPUT

Figure 62. Timing Waveforms

Figure 63 shows the quiescent power of the ADA4805-1/

ADA4805-2 with and without the power scaling. Without power

scaling, the ADA4805-1/ADA4805-2 consumes constant power

regardless of the sampling frequency, as shown in Equation 1.

(1)

With power scaling, the quiescent power becomes proportional

S

ON

AMP

S

Q

Q

t

t

V

I

P

,







(2)

Thus, by dynamically switching the ADA4805-1/ADA4805-2

between shutdown and full power modes between consecutive

samples, the quiescent power of the driver scales with the

sampling rate.

10

100

1000

10000

100000

10

100

1k

10k

100k

1M

ADC SAMPLING FREQUENCY (Hz/s)

ADA4805-1/ADA4805-2, 6V SINGLE SUPP LY

ON TIME = 3µs

ADA4805-1/ADA4805-2

ON TIME = 3µs

AD7980 (ADC)

ADA4805-1/ADA4805-2

CONTINUOUSLY ON

Figure 63. Quiescent Power Consumption of the ADA4805-1/ADA4805-2 vs.

ADC Sampling Frequency