ADAS3022 datasheet(30/40 Pages) AD

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ADAS3022

Data Sheet

Rev. A | Page 30 of 40

High Voltage Supplies

The high voltage bipolar supplies (VDDH and VSSH) are

required and must be at least 2.5 V larger than the maximum

input. For example, the supplies should be ±15 V for headroom

in the ±24.576 V differential input range. Sufficient decoupling

of these supplies is also required, consisting of at least a 10 μF

capacitor and a 100 nF capacitor on each supply.

Power Dissipation Modes

The ADAS3022 offers two power dissipation modes: fully

operational mode and power-down mode.

Fully Operational Mode

In fully operational mode, the ADAS3022 can perform

conversions as soon as all internal bias currents are established.

Power-Down Mode

To minimize the operating currents of the device when it is idle,

place the device in full power-down mode by bringing the PD

input high. This places the ADAS3022 into a deep sleep mode, in

which CNV activity is ignored and the digital interface is inactive.

Refer to the Reset and Power-Down (PD) Inputs section for

timing details. In deep sleep mode, the internal regulators

(ACAP, RCAP, and DCAP) and the voltage reference are also

powered down. To reestablish operation, return PD low. Note

that before the device can operate at the specified performance, the

reference voltage must charge up the external reservoir

capacitor(s) and

be allowed the specified settling time. Returning PD low also

resets the ADAS3022 digital core, including the CFG register, to

its default state. Therefore, the desired CFG must be rewritten

to the device and two dummy conversions must be completed

before the device operation is restored to the configuration

programmed prior to PD assertion.

CONVERSION MODES

The ADAS3022 offers two conversion modes to accommodate

varying applications. The mode is set with the conversion mode

select bit (CMS, Bit 1 of the CFG register).

Warp Mode (CMS = 0)

Setting CMS to 0 is useful when an aggregate throughput rate of

1 MSPS is required. However, in this mode, the maximum time

between conversions is restricted. If this maximum period is

exceeded, the conversion result may be corrupted. Therefore,

this mode is more suitable for continually sampled applications.

Normal Mode (CMS = 1, Default)

Setting CMS to 1 is useful for all applications with a maximum

aggregate throughput of 900 kSPS. In this mode, there is no

restriction in terms of the maximum time between conversions.

This mode is the default condition from the assertion of an

asynchronous RESET. The main difference between normal

mode and warp mode is the BUSY time; tQUIET is slightly longer

in normal mode than it is in warp mode.

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