Datasheet
ADAS3022 Data Sheet
Rev. B | 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; t
QUIET
is slightly longer
in normal mode than it is in warp mode.