X9530 datasheet(8/30 Pages) XICOR

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X9530

Characteristics subject to change without notice.

8 of 30

REV 3.7 8/26/04

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VOLTAGE REFERENCE

The voltage reference to the A/D and D/A converters

on the X9530, may be driven from the on-chip voltage

reference, or from an external source via the VRef pin.

Bit VRM in Control Register 0 selects between the two

options (See Figure 2).

The default value of VRM is “0”, which selects the

internal reference. When the internal reference is

selected, it’s output voltage is also an output at pin

VRef with a nominal value of 1.21 V. If an external

voltage reference is preferred, the VRM bit of the

Control Register 0 must be set to “1”.

Figure 2. Voltage Reference Structure

A/D CONVERTER

The X9530 contains a general purpose, on-chip, 6-bit

Analog to Digital (A/D) converter whose output is

available at the Status Register as bits AD[5:0]. By

default these output bits are used to select a row in the

look-up tables associated with the X9530’s Current

Generators. When bit ADCfiltOff is “0” (default), bits

AD[5:0] are updated each time the ADC performs four

consecutive conversions with the same exact result.

When bit ADCfiltOff is “1”, these bits are updated after

every ADC conversion.

A block diagram of the A/D converter is shown in

Figure 3. The voltage reference input (see “VOLTAGE

REFERENCE”

for

details),

sets

the

maximum

amplitude of the ramp generator output. The A/D

converter input signal (see “A/D Converter Input

Select” below for details) is compared to the ramp

generator output. The control and encode logic

produces a binary encoded output, with a minimum

value of 00h (010), and a full scale output value of 3Fh

(6310).

The A/D converter input voltage range (VINADC) is

from 0 V to V(VRef).

A/D Converter Input Select

The input signal to the A/D converter on the X9530,

may be the output of the on-chip temperature sensor,

or an external source via the VSense pin. Bit ADCIN in

Control register 0 selects between the two options (See

Figure 4). It’s default value is “0”, which selects the

internal temperature sensor.

If an external source is intended as the input to the A/D

converter, the ADCIN bit of the Control register 0 must

be set to “1”.

VRM: bit 2 in Control register 0.

VRef Pin

On-chip

A/D Converter and

Voltage

Reference

D/A Converters reference

Figure 3. A/D Converter Block Diagram

Ramp

Generator

A/D Converter Input

From VRef

Clock

Control and

Encode Logic

Conversion Reset

A/D Converter

Output

(To LUTs

and Status

Comparator

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