Decimal to Thermometer Encoder

This article contains Verilog-A model for Decimal to Thermometer encoder. This block can be used for behavioral simulation of the pipelined ADCs, programmable gains/BW etc. This model will automatically select number of outputs based on selected number of input binary bits. Usage:

1. Create a new cell in Library Manager named dec2therm and select cell type Verilog A;
2. Copy and paste the code provided;
3. Specify therm_bits variable to be the desired thermometer bits number;
4. Specify Start_Bit to be 0 if you want thermometer code to start from 0 or 1 if you want thermometer code to start from 1;
5. Perform Check and Save;
6. A cell symbol will be created;
7. Instantiate dec2term cell into your design;
8. Perform Check and Save and run the simulation.

Cell name: dec2term Model type: Verilog-A

Example: therm_bits = 4, Start_Bit = 0

Example: therm_bits = 4, Start_Bit = 1

1// Decimal to Thermometer decoder
2// Implements two options: 
3// Start_Bit = 0: Decimal 0 equals thermometer 0
4// Start_Bit = 1: Decimal 0 equals thermometer 1
5// Change therm_bits variable for your needs!
6// Author: A. Sidun
7// Source: AnalogHub.ie
8
9`include "constants.vams"
10`include "disciplines.vams"
11`define therm_bits 10						// define number of output bits here
12
13module dec2therm(out);
14
15output [`therm_bits-1:0] out;
16voltage [`therm_bits-1:0] out;
17
18parameter real vdd = 5;					// voltage level of logic 1 (V)
19parameter real vss = 0;					// voltage level of logic 0 (V)
20parameter integer Decimal_Code = 5; 	// input decimal code
21parameter integer Start_Bit = 0;    	// defines if thermometer starts from 0 or 1
22
23real dout[`therm_bits-1:0];					// internal result variable
24genvar i;
25
26analog begin
27
28case (Start_Bit)
29    0: begin	// Decimal 0 equals thermometer 0
30		for(i=1;i<`therm_bits+1;i=i+1) begin
31          		if(Decimal_Code!=i) begin
32              		dout[i-1]=vss;
33          		end
34      		else begin
35          		dout[i-1]=vdd;
36      		end
37		end
38	end 
39
40    1: begin	// Decimal 0 equals thermometer 1
41		for(i=0;i<`therm_bits;i=i+1) begin
42          		if(Decimal_Code!=i) begin
43              		dout[i]=vss;
44          		end
45      		else begin
46          		dout[i]=vdd;
47      		end
48		end
49	end
50endcase
51
52// Plotting outputs
53for (i=0; i<`therm_bits; i=i+1)
54	    V(out[i]) <+ transition(dout[i],0,0);
55end
56
57endmodule