ADS5541IPAPR datasheet(24/37 Pages) TI1

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OCM

INP

INM

0.1

µF

0.1

µF

+3.3V

+5V

0.1

µF

−5V

THS4503

Ω

ADS5541

14-Bit / 105MSPS

POWER-SUPPLY SEQUENCE

REFERENCE CIRCUIT

AVDD

REFP

Ω

µF

POWER-DOWN

R EF P

R EF M

IR EF

Ω

56k

Ω

µF

Production Data

ADS5541

SBAS307C – MAY 2004 – REVISED FEBRUARY 2007

Figure 42. Using the THS4503 with the ADS5520

Using the serial interface PDN bit to power down the

device places the outputs in a high-impedance state

and only the internal reference remains on to reduce

The preferred mode of power-supply sequencing is

the power-up time. The power-down mode reduces

to power up AVDD first, followed by DRVDD. Raising

power dissipation to approximately 180mW.

both

supplies

simultaneously

also

valid

power-supply sequence. In the event that DRVDD

powers up before AVDD in the system, AVDD must

power up within 10ms of DRVDD. Optionally, it is

The

ADS5541

has

built-in

internal

reference

recommended to put a 2k

Ω resistor from REFP (pin

generation, requiring no external circuitry on the

29)

AVDD as shown in Figure 43. This

printed

circuit

board

(PCB).

For

optimum

configuration helps to make the device more robust

performance, it is best to connect both REFP and

to power supply ramp-up timings.

REFM to ground with a 1

µF decoupling capacitor

(the 1

Ω resistor shown in Figure 44 is optional). In

addition, an

external

56k

Ω resistor should be

connected from IREF (pin 31) to AGND to set the

proper current for the operation of the ADC, as

shown in Figure 44. No capacitor should

connected between pin 31 and ground; only the

56k

Ω resistor should be used.

Figure 43.

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

either by reducing the clock speed or by setting the

PDN bit via the serial programming interface. Using

the reduced clock speed, power-down may be

initiated for clock frequency below 2MSPS. The

exact frequency at which the power-down occurs

varies from device to device.

Figure 44. REFP, REFM, and IREF Connections

for Optimum Performance

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