ADAS3023 datasheet(24/32 Pages) AD

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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

100nF

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

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