Datasheet

ADAS3023 Data Sheet
to buffer the external reference voltage and, thereby, reduce SAR
conversion crosstalk.
The voltage reference temperature coefficient (TC) directly
affects the full-scale accuracy of the system; therefore, in
applications where full-scale accuracy is crucial, care must be
taken with the TC. For example, a ±15 ppm/°C TC of the
reference changes the full-scale accuracy by ±1 LSB/°C.
POWER SUPPLY
The ADAS3023 uses five supplies: AVDD, DVDD, VIO, VDDH,
and VSSH (see Table 9). Note that the ACAP, DCAP, and RCAP
pins are for informational purposes only because they are the
outputs of the internal supply regulators.
Table 9. Supplies
Mnemonic Function Required
AVDD Analog 5 V core Yes
DVDD Digital 5 V core Yes, or can connect to
AVDD
VIO
Digital input/output
Yes, and can connect to
DVDD (for the 5 V level)
VDDH Positive high voltage Yes, +15 V typical
VSSH Negative high
voltage
Yes, −15 V typical
ACAP Analog 2.5 V core No, on chip
DCAP
Digital 2.5 V core
No, on chip
RCAP Analog 2.5 V core No, on chip
Core Supplies
The AVDD and DVDD pins supply the ADAS3023 analog and
digital cores, respectively. Sufficient decoupling of these supplies is
required, consisting of at least a 10 μF capacitor and 100 nF capaci-
tor on each supply. Place the 100 nF capacitors as close as possible
to the ADAS3023. To reduce the number of supplies that are
required, supply the DVDD from the analog supply by connecting
a simple RC filter between AVDD and DVDD, as shown in
Figure 45.
Figure 45. Supply Connections
VIO is the variable digital input/output supply and allows direct
interface with any logic between 1.8 V and 5 V (DVDD supply
maximum). To reduce the supplies that are required, VIO can,
alternatively, be connected to DVDD when DVDD is supplied
from the analog supply through an RC filter. The recommended
low dropout regulators are ADP3334, ADP1715, ADP7102, and
ADP7104 for the AVDD, DVDD, and VIO supplies. Note that
the user must bring up the ADAS3023 power supplies in the
following sequence:
1. VIO
2. VDDH
3. VSSH
4. DVDD
5. AVDD
6. REFx
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
operating input voltage. Specifically, any operating input voltage
(as defined in Table 2) of an input pin requires 2.5 V of headroom
from the VDDH/VSSH supplies or
(VSSH + 2.5 V) ≤ INx/COM ≤ (VDDH − 2.5 V)
Sufficient decoupling of these supplies is also required, consisting
of at least a 10 μF capacitor and 100 nF capacitor on each supply.
POWER DISSIPATION MODES
The ADAS3023 offers two power dissipation modes: fully
operational mode and power-down mode.
Fully Operational Mode
In fully operational mode, the ADAS3023 can perform the
conversions normally.
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 ADAS3023 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
powered down.
To reestablish operation, return PD to logic 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. RESET must be applied after
returning PD to low to restore the ADAS3023
digital core, includ-
ing the CFG register, to its default state. Therefore, the desired CFG
must be rewritten to the device and one dummy conversion must
be completed before the device operation is restored to the config-
uration programmed prior to PD assertion. Note that when using
the internal reference, sufficient time is required to settle it to
the nominal value. For a typical connection, it requires 100 ms
to settle to the nominal value (see Figure 41).
+
AVDD
AGND DVDD DGND
10µF
+
10µF
100nF100nF
20Ω
+5V DIGITAL
SUPPLY
+5V ANALOG
SUPPLY
VIO
+
10µF
+1.8V TO +5V
DIGITAL I/O
SUPPLY
100nF
+15V
–15V
+
10µF
100nF
+
10µF
100nF
VDDH
VSSH
ADAS3023
DGND
10942-016
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