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POWER SUPPLY SEQUENCING

POWER DOWN

ADS5500

SBAS303F – DECEMBER 2003 – REVISED FEBRUARY 2007

Table 4. Recommended Amplifiers to Drive the Input of the ADS5500

INPUT SIGNAL FREQUENCY

RECOMMENDED AMPLIFIER

TYPE OF AMPLIFIER

USE WITH TRANSFORMER?

DC to 20 MHz

THS4503

Differential In/Out Amp

No

DC to 50 MHz

OPA847

Operational Amp

Yes

DC to 100 MHz

THS4509

Differential In/Out Amp

NO

OPA695

Operational Amp

Yes

10 MHz to 120 MHz

THS3201

Operational Amp

Yes

THS3202

Operational Amp

Yes

Over 100 MHz

THS90016

RF Gain Block

Yes

Figure 43. Converting a Single-Ended Input Signal to a Differential Signal Using an RF Transformer

Figure 44. Using the THS4503 With the ADS5500

The preferred power-up sequence is to ramp AVDD

The device enters power-down in one of two ways:

first, followed by DRVDD, including a simultaneous

either by reducing the clock speed or by setting the

ramp of AVDD and DRVDD. In the case that DRVDD

PDN bit through the serial programming interface.

ramps up first in the system, care must be taken to

Using the reduced clock speed, power-down may be

ensure that AVDD ramps up within 10 ms.

initiated for clock frequencies below 2 Msps. The

exact frequency at which the power down occurs

varies from device to device.

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