ADAS3022 datasheet(29/40 Pages) AD

29 / 40 page

Data Sheet

ADAS3022

Rev. A | Page 29 of 40

Reference Decoupling

With any of the reference topologies described in the Voltage

Reference Input/Output section, the REF1 and REF2 reference

pins of the ADAS3022 have dynamic impedances and require

sufficient decoupling, regardless of whether the pins are used as

inputs or outputs. This decoupling usually consists of a low ESR

capacitor connected to each REF1 and REF2 and to the accom-

panying REFN return paths. Using X5R, 1206 size ceramic chip

capacitors is recommended for decoupling in all the reference

topologies described in the Voltage Reference Input/Output section.

The placement of the reference decoupling capacitors plays an

important role in the system performance. Mount the decoupling

capacitors on the same side as the ADAS3022, close to the REF1

and REF2 pins, with thick PCB traces. Route the return paths to the

REFN inputs, which are in turn connected to the analog ground

plane of the system. The resistance of the return path to ground

should be minimized by using as many through vias as possible

when it is necessary to connect to an internal PCB layer.

The REFN and RGND inputs should be connected with the

shortest distance to the analog ground plane of the system,

preferably adjacent to the solder pads, using several vias. One

common mistake is to route these traces to an individual trace

that connects to the ground of the system. This can introduce

noise, which may adversely affect LSB sensitivity. To prevent

such noise, it is highly recommended to use PCBs with multiple

layers, including ground planes, rather than using single- or

double-sided boards. Refer to UG-484 for more information

about the PCB layout of the EVAL-ADAS3022EDZ.

For applications that use multiple ADAS3022 devices or other

PulSAR ADCs, it is more effective to use the internal reference

buffer to buffer the external reference voltage, thus reducing

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 ADAS3022 uses five supplies: AVDD, DVDD, VIO, VDDH,

and VSSH (see Table 9). Note that ACAP, DCAP, and RCAP are

included in Table 9 for informational purposes only because these

supplies are outputs of the on-chip supply regulators. Refer to

UG-484 for more information about how these supplies are

generated on the EVAL-ADAS3022EDZ.

Table 9. Power Supplies

Name

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 5 V

level)

VDDH

Positive high voltage

Yes, +15 V typ

VSSH

Negative high voltage

Yes, −15 V typ

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

AVDD and DVDD supply the ADAS3022 analog and digital

cores, respectively. Sufficient decoupling of these supplies is

required, consisting of at least a 10 μF capacitor and a 100 nF

capacitor on each supply. The 100 nF capacitors should be

placed as close as possible to the ADAS3022. To reduce the

number of supplies needed, DVDD can be supplied from the

analog supply by connecting a simple RC filter between AVDD

and DVDD, as shown in Figure 65.

VIO is the variable digital input/output supply and can be

directly interfaced to any logic between 1.8 V and 5 V (DVDD

supply maximum). To reduce the supplies needed, 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, and ADP7102/

ADP7104 for the AVDD, DVDD, and VIO supplies.

AVDD

10µF

100nF

AGND

DGND

DVDD

ADAS3022

VIO

1.8V TO 5V

DIGITAL I/O

SUPPLY

ANALOG

SUPPLY

+5V

+5V DIGITAL

SUPPLY

10µF

Ω

VDDH

VSSH

10µF

100nF

+15V

–15V

10µF

100nF

Figure 65. ADAS3022 Supply Connections

ADAS3022 数据表(PDF) 29 Page - Analog Devices

ADAS3022 数据表(HTML) 29 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

数据表下载

链接网址

ADAS3022 数据表(PDF) 29 Page - Analog Devices

ADAS3022 数据表(HTML) 29 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

数据表 下载

链接网址

数据表下载