HI2303EVAL1【PDF 1/14 页】EVALUATION BOARD HI2303

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HI2303 Evaluation Board

Application Note

March 1998

AN9783.1

Introduction

The HI2303 evaluation kit can be used to examine the

performance of the HI2303 triple 8-bit analog to digital con-

verter (ADC). The evaluation board includes a buffered clock

driver, voltage reference, triple A/D converter, data latches and

triple D/A converter (DAC). Please refer to the functional block

diagram in Figure 1.

Evaluation Board

The HI2303 evaluation board is a four layer board with a lay-

out optimized for the best performance of the ADC. The opti-

mization includes segmenting the analog and digital signals

to prevent digital noise from degrading the analog-to-digital

conversion process. The physical board is divided into an

analog and digital area with supporting analog and digital

ground planes. The power supplies hook-up is detailed in

Table 1.

Included in the application note is an electrical schematic of

the evaluation board circuitry, a components layout, a com-

ponents part list and views of the various board layers that

make up the printed wiring board. Please refer to Figures 2

through 8. The user should feel free to copy the layout in

their application. Refer to the components layout and the

evaluation board electrical schematics for the following

discussions.

Table 1 lists the operational supply voltages for the evaluation

board. Single supply operation of the converter is possible but

the overall performance of the converter may degrade.

capacitors. To bias the inputs at the desired 0.5 to 2.5V

range bias tees are provided and can be set via potentiome-

ters R24, R25 and R26. In addition, jumpers JP21, JP22 and

JP23 may removed to disconnect the bias tee. Care should

be taken to ensure the inputs do not exceed the absolute

maximum ratings of the ADC.

Reference Voltage Circuit

The analog input range of the HI2303 is set by the voltage

between V RT and V RB . The voltage can either be internally

generated or for increased accuracy externally provided.

Please refer to table 2 for the appropriate jumpers on the eval-

uation board to ENSURE the internal and external reference

are not enabled at the same time to prevent permanent

damage to the HI2303.

Internal reference

The internal reference is enabled by connecting V RBS to

ANGD and V RTS to AV DD . The HI2303 will then generate

approximately 2.5V and 0.6V for V RT and V RB respectively.

An external voltage reference is also provided on the board.

External Reference

The external reference section contains two circuits which

generate the top (V RT ) and bottom (V RB ) voltages. The preci-

sion reference is derived by using the Intersil ICL7663S

programmable voltage regulator. For complete design theory

please refer to the ICL7663 datasheet. As detailed in the

datasheet, the output of the voltage regulator is defined in

Equation 1. In addition, the sense pin is used along with the

TABLE 1. EVALUATION BOARD POWER SUPPLIES

10 ?

resistors to provide short circuit protection of

POWER

NOMINAL

CURRENT

FUNCTION(S)

approximately 44mA.

SUPPLY

AVDD

VALUE

5.0V ± 5%

(TYP)

170

SUPPLIED

Analog power to ADC,

V REF = V SET ( R + R2/R1 )

(EQ. 1)

Reference and DAC.

V RT

AGND

Analog Ground

The top reference is derived by U3 and the supporting

DVDD

5.0V ± 5%

Digital power to ADC, Clock,

components which enables V RT to be adjusted, via the vari-

Latches and DAC.

able resistor R17, from 1.25V to approximately 2.7V. The

DGND

Analog Input

Digital Ground

nominal voltage of V RT should be set to 2.5V.

V RB

The bottom reference is derived by U4 and the supporting

The analog inputs to the HI2303 are obtained via BNC

connectors J1, J2 and J3 for A IN , B IN and C IN respectively.

The input is terminated by a 75 ? resistor and DC blocked by

components which allows V RB to be adjusted, via the variable

resistor R21, from 0V to approximately 2.5V. The nominal

voltage of V RB should be set to 0.5V.

1-888-INTERSIL or 321-724-7143 | Copyright

? Intersil Corporation 1999

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