CS4373A-ISZ 데이터 시트보기 (PDF) - Cirrus Logic

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CS4373A-ISZ

Low-power, High-performance ∆Σ Test DAC

Cirrus Logic 

CS4373A

To VA+

Regulator

100 µF

To VA-

Regulator

100 µF

0.1 µF

2.500 V

VREF

10 Ω

0.1 µF

Route VREF± as a differential pair

from the 100uF RC filter capacitor

+ 100 µF

To VREF+

0.1 µF

0.1 µF

To VREF-

0.1 µF

Figure 13. Voltage Reference Circuit

8. VOLTAGE REFERENCE

The CS4373A requires a 2.500 V precision

voltage reference to be supplied to the VREF±

pins.

8.1 VREF Power Supply

To guarantee proper regulation headroom for

the voltage reference device, the voltage refer-

ence GND pin should be connected to VA- in-

stead of system ground, as shown in

Figure 13. This connection results in VREF-

voltage equal to VA- and VREF+ voltage very

near ground potential [(VA-) + 2.500 VREF].

Power supply inputs to the voltage reference

device should be bypassed to system ground

with 0.1 µF capacitors placed as close as pos-

sible to the power and ground pins. In addition

to 0.1 µF local bypass capacitors, at least

100 µF of bulk capacitance to system ground

should be placed on each power supply near

the voltage regulator outputs. Bypass capaci-

tors should be X7R, C0G, tantalum, or other

high-quality dielectric type.

8.2 VREF RC Filter

A primary concern in selecting a precision volt-

age reference is noise performance in the

measurement bandwidth. The Linear Technol-

ogy LT1019AIS8-2.5 voltage reference yields

acceptable noise levels if the output is filtered

with a low-pass RC filter.

A separate RC filter is required for each sys-

tem device connected to a given voltage refer-

ence. By sharing a common RC filter, signal-

dependent sampling of the voltage reference

by one system device could cause unwanted

tones to appear in the measurement band-

width of another system device via common

impedance coupling.

8.3 VREF PCB Routing

To minimize the possibility of outside noise

coupling into the CS4373A voltage reference

input, the VREF± traces should be routed as a

differential pair from the large capacitor of the

voltage reference RC filter. Careful control of

the voltage reference source and return cur-

rents by routing VREF± as a differential pair

will improve immunity from external noise.

To further improve noise rejection of the

VREF± routing, include 0.1 µF bypass ca-

pacitors to system ground as close as possible

to the VREF+ and VREF- pins of the

CS4373A.

26

DS699F2

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