CS5509(1995) View Datasheet(PDF) - Cirrus Logic

Part Name

Description

Manufacturer

CS5509
(Rev.:1995)

Single Supply, 16-Bit A/D Converter

Cirrus Logic 

CDB5509

Introduction

The CDB5509 evaluation board provides a quick

means of testing the CS5509 A/D converter. The

CS5509 converter requires a minimal amount of

external circuitry. The evaluation board comes

configured with the A/D converter chip operat-

ing from a 32.768 kHz crystal and with an

off-chip precision 2.5 volt reference. The board

provides access to all of the digital interface pins

of the CS5509 chip.

Evaluation Board Overview

The board provides a complete means of making

the CS5509 A/D converter chip function. The

user must provide a means of taking the output

data from the board in serial format and using it

in his system.

Figure 1 illustrates the schematic for the board.

The board comes configured for the A/D con-

verter chip to operate from the 32.768 kHz

watch crystal. A BNC connector for an external

clock is provided on the board. To connect the

external BNC source to the converter chip, a cir-

cuit trace must be cut. Then a jumper must be

inserted in the proper holes to connect the XIN

pin of the converter to the input line from the

BNC. The BNC input is terminated with a 50Ω

resistor. Remove this resistor if driving from a

logic gate. See the schematic in Figure 1.

The board comes with the A/D converter VREF+

and VREF- pins hard-wired to the 2.5 volt

bandgap voltage reference IC on the board.

All of the control pins of the CS5509 are avail-

able at the J1 header connector. Buffer ICs U2

and U3 are used to buffer the converter for inter-

face to off-board circuits. The buffers are used

on the evaluation board only because the exact

loading and off-board circuitry is unknown.

Most applications will not require the buffer ICs

for proper operation.

To put the board in operation, select either bipo-

lar or unipolar mode with DIP switch S2. Then

press the CAL pushbutton after the board is

powered up. This initiates calibration of the con-

verter which is required before measurements

can be taken. With CONV high (S2-3 open) the

converter will convert continuously. Figure 3 il-

lustrates the CAB5509 adapter board. The

CAB5509 translates a CS5505 pinout to a

CS5509 pinout.

Figures 4 and 5 illustrate the evaluation board

layout while Figure 6 illustrates the component

placement (silkscreen) of the evaluation board.

24

DS125DB1

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