AD7626 datasheet(21/28 Pages) AD

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AD7626

Rev. A | Page 21 of 2

Wake-Up Time from EN1= 0, EN0 = 0

The AD7626 powers down when EN1 and EN0 are both set to

0. Selecting the correct reference choice from power-down, the

user sets EN1 and EN0 to the required value shown in Table 8.

The user may immediately apply CNV pulses to receive data

conversion results. Typical wake-up times for the selected

reference settings are shown in Table 9. Each time represents

the duration from the EN1, EN0 logic transition to when the

output of the ADC is settled to 0.5 LSB accuracy.

Table 9. Wake-Up Time from EN1=0, EN0 = 0

Reference Mode

EN1

EN0

Wake-Up

Time (0.5 LSB

Accuracy)

Power-up

Internal reference and inter-

nal reference buffer in use

9.5 sec

External 1.2 V reference

applied to REFIN pin

25 ms

External 4.096 V reference

applied to REF pin

65 μs

POWER SUPPLY

The AD7626 uses both 5 V (VDD1) and 2.5 V (VDD2) power

supplies, as well as a digital input/output interface supply (VIO).

VIO allows a direct interface with 2.5 V logic only. VIO and

VDD2 can be taken from the same 2.5 V source; however, it is

best practice to isolate the VIO and VDD2 pins using separate

traces as well as to decouple each pin separately.

The 5 V and 2.5 V supplies required for the AD7626 can be

generated using Analog Devices, Inc., LDOs such as

the ADP3330-2.5, ADP3330-5, ADP3334, and ADP1708.

100

10k

SUPPLY FREQUENCY (Hz)

INTERNAL REFERENCE USED

VDD2

VDD1

Figure 38. PSRR vs. Supply Frequency

(350 mV pp Ripple on VDD2, 600 mV Ripple on VDD1)

Power-Up

When powering up the AD7626 device, first apply the 2.5 V

VDD2 supply and VIO voltage to the device. After the VIO and

2.5 V VDD2 have been established, apply the 5 V VDD1 supply.

If using an external reference with the AD7626, ensure that the

EN0 and EN1 pins are connected to the correct logic values

associated with the reference option of choice and then apply

the external reference voltage. Finally, apply the analog inputs to

the ADC.

THROUGHPUT (MSPS)

VDD1 EXTERNAL

REFERENCE

VDD1 INTERNAL

REFERENCE

VDD2 INTERNAL

REFERENCE

VDD2 EXTERNAL

REFERENCE

VIO EXTERNAL

REFERENCE

VIO INTERNAL

REFERENCE

Figure 39. Current Consumption vs. Sampling Rate

160

140

120

100

THROUGHPUT (MSPS)

INTERNAL REFERENCE

EXTERNAL REFERENCE

Figure 40. Power Dissipation vs. Sampling Rate

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