Cirrus-logic CRD5381 Uživatelský manuál stáhnout pdf (Strana 11)

DS563RD1 11

CRD5381

Figure 7. Status Indicator and Reset Header, J16

2.6 Analog Inputs

The CRD5381 provides four fully differential analog inputs via J9, J11, J7, and J12; shown in Figure 9 and

Figure 10. Each analog input has the required analog circuitry to optimize the performance of each CS5381.

The input buffer to each CS5381 device has unity gain, and the CRD5381 differential input amplitude re-

quired to generate a full-scale digital output is typically 5.65 Vpp.

If extra analog input circuitry is required in the user’s design, it should drive a buffer equivalent to the con-

tents of the dotted boxes shown in Figure 9 and in Figure 10 labeled “CS5381 Required Input Circuitry”. In

this case, all components outside the dotted boxes in Figure 9 and Figure 10 should be removed from the

design.

2.7 Power

The CRD5381 requires the user to supply +3.3 V (J6) and ±12 V (J2 and J1) to the board. Onboard regula-

tors supply the required +5 V and +2.5 V. All voltage inputs must be referenced to the single black banana-

type ground connector (J5). Zener Diodes Z1 and Z2 (shown in Figure 14) are used to protect the CRD5381

circuitry from accidental connection of a reversed polarity supply or a supply of over ± 13 V to J1 and J2.

WARNING: Please refer to the CS5381 and CS8421 data sheet for allowable voltage levels.

2.8 Grounding and Power Supply Decoupling

The CS5381 and CS8421 require careful attention to power supply and grounding arrangements in order

to optimize performance. Figure 8 provides an overview of the connections on the CRD5381; Figure 15

shows the component placement. Figure 16 shows the top layout, Figure 17 shows the bottom layout, Fig-

ure 18 shows the power plane, and Figure 19 shows the ground plane. The decoupling capacitors are lo-

cated as close to the CS5381 and CS8421 as possible. Extensive use of ground plane fill in the evaluation

board yields large reductions in radiated noise.

OVERFLOW A

OVERFLOW B

SRC UNLOCK A

RESET

Signal Ground

J16

SRC UNLOCK B

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Cirrus-logic CRD5381 Uživatelský manuál Strana 11