X96010 datasheet(15/26 Pages) RENESAS

15 / 26 page

FN8214.1

October 25, 2005

A/D Converter Range

From Figure 6 we can see that the operating range of the

A/D converter input depends on the voltage reference.

The table below summarizes the voltage range

restrictions on the VSense and VRef pins in different

configurations :

VSense and VRef ranges

LOOK-UP TABLES

The X96010 memory array contains two 64-byte look-

up tables. One is associated to pin I1’s output current

generator and the other to pin I2’s output current gen-

erator, through their corresponding D/A converters.

The output of each look-up table is the byte contained

in the selected row. By default these bytes are the

inputs to the D/A converters driving pins I1 and I2.

The byte address of the selected row is obtained by

adding the look-up table base address (90h for LUT1,

and D0h for LUT2) and the appropriate row selection

bits. See Figure 8.

By default the look-up table selection bits are the

6 MSBs of the A/D converter output. Alternatively,

the A/D converter can be bypassed and the six row

selection bits are the six LSBs of Control Registers

1 and 2, for the LUT1 and LUT2 respectively. The

selection between these options is illustrated in Fig-

ure 9, and described in “I2DS: Current Generator 2

Direction Select Bit (Non-volatile)” on page 12, and

“Control Register 2” on page 12.

CURRENT GENERATOR BLOCK

The Current Generator pins I1 and I2 are outputs of

two independent current mode D/A converters.

D/A Converter Operation

The Block Diagram for each of the D/A converters is

shown in Figure 7.

The input byte of the D/A converter selects a voltage

on the non-inverting input of an operational amplifier.

The output of the amplifier drives the gate of a FET,

whose source is connected to ground via resistor R1

or R2. This node is also fed back to the inverting input

of the amplifier. The drain of the FET is connected to

the output current pin (I1 or I2) via a “polarity select”

circuit block.

VRef

A/D Converter Input

Ranges

Internal

VSense Pin

 V(VSense) 

V(VRef)

External

VSense Pin

V(VRef)  1.3 V

 V(VSense) 

V(VRef)

All voltages referred to Vss.

X96010

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