XRD6406 查看數據表（PDF） - Exar Corporation

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XRD6406

CMOS 6 MSPS, 10-Bit, High Speed Analog-to-Digital Converter

Exar Corporation 

XRD6406

1023

768

V4

512

V3

256

V2

V1

0

1V

2V

3V

4V

VIN

Figure 7. A Piece Wise Linear, Logarithmic

Transfer Function

APPLICATION NOTES

Signals should not exceed AVDD or DVDD +0.5V or go below

DGND or AGND --0.5V. All pins have internal protection diodes

that will protect them from short transients (<100ms) outside the

supply range.

AGND and DGND pins are connected internally through the P--

substrate. DC voltage differences between these pins will

cause undesirable internal substrate currents.

The power supply (AVDD) and reference voltage (VRT & VRB)

pins should be decoupled with 0.1mF and 10mF capacitors to

AGND, placed as close to the chip as possible.

The digital outputs should not drive long wires or buses. The

capacitive coupling and reflections will contribute noise to the

conversion.

VIN Analog Input

This part has a switched capacitor type input circuit. This means

that the input impedance changes with the phase of the input

clock. VIN is sampled at the high to low clock transition.

Figure 8. shows an equivalent input circuit.

AVDD

VIN

AGND

160W CLK

18pF 100W

5pF

VRT + VRB +

2

-

CLK

1.5pF

CLK

Figure 8. Equivalent Input Circuit

RTS & RBS Internal Bias Resistors

Two matched resistors are provided on the chip. These resistors

can be used to generate on chip reference voltages. Each

resistor has a value equal to 1/3 of the reference ladder resistor.

By connecting RTS to VRT, and connecting RBS to VRB, the

reference ladder will be biased to 1V at VRB and 4V at VRT.

If the internal reference pins VRTS and/or VRBS are not used they

should be left unconnected.

R1 thru R3 Reference Ladder Taps

These taps connect to every quarter point along the reference

ladder; R1 is 1/4th up from VRB, R3 is 3/4ths up from VRB (or

1/4th down from VRT). Normally these pins should have 0.1

microfarad capacitors to AGND; this helps reduce the INL errors

by stabilizing the reference ladder voltages. These taps can

also be used to alter the transfer curve of the ADC. A four

segment, piecewise linear, custom transfer curve can be

designed by connecting voltage sources to these pins.

Rev. 1.00

7

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