Converters

Analog to Digital Converter
Digital to Analog Converter

Analog to Digital Converter

The analog-digital converter converts an analog value Vin into a two-bit digital value called A0,A1. The flash converter uses three converters and a coding logic to produce A0 and A1. A very complex logic circuit and 255 comparators would be used for an ADC eight-bit flash.

The polysilicon has a high resistance (50 per square) and can be used as a resistor network, which generates intermediate voltage references used by the voltage comparators located in the middle.

The ADC converts an analog Vin in 2 bits A0, A1
Resistor scale in polysilicon
To produce A0, A1 the ADC needs 2 comparators and 3 logic gates
For a 8 bits CAN, 255 comparators are necessary

Analog Input Vin	C0	C1	C2	A1	A0
Vin<1.25V	0	0	0	0	0
1.25<Vin<2.5	1	0	0	0	1
2.5<Vin<3.5	1	1	0	1	0
Vin>3.75V	1	1	1	1	1

Digital to Analog Converter

This digital-analog converter converts a digital three-bit input (A0,A1,A2) into an analog value Vout.

The polysilicon resistive net gives intermediate voltage references which flow to the output via a transmission gate net. The resistance symbol is inserted in the layout to indicate to the simulator that an equivalent resistance must be taken into account for the analog simulation.

This DAC converts 3 bits A0, A1, A2 into an analog voltage Vin
Resistor scale in polysilicon
Structure : 14 transmission gates

A2	A1	A0	Analog output Vout (V)
0	0	0	0.0 V
0	0	1	0.625
0	1	0	1.25
0	1	1	1.875
1	0	0	2.5
1	0	1	3.125
1	1	0	3.75
1	1	1	4.375