Binary-to Thermometer Encoder model

This page contains Verilog-A model of the binary-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 bin2therm and select cell type Verilog A;
2. Copy and paste the code provided;
3. Specify binary_bits variable to be the desired binary 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 bin2term cell into your design;
8. Perform Check and Save and run the simulation.

Cell name: bin2term Model type: Verilog-A

Example: binary_bits = 2, Start_Bit = 0

Example: binary_bits = 2, Start_Bit = 1

1// Binary 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 binary_bits variable for your needs!
6// Author: A. Sidun
7// Source: AnalogHub.ie
8
9`include "constants.vams"
10`include "disciplines.vams"
11`define binary_bits 4							// define number of binary bits here
12
13module bin2therm(in,out);
14input [`binary_bits-1:0] in;
15output [2**`binary_bits-1:0] out;
16
17voltage [`binary_bits-1:0] in;
18voltage [2**`binary_bits-1:0] out;
19
20parameter real vdd = 1;					// voltage level of logic 1 (V)
21parameter real vss = 0;					// voltage level of logic 0 (V)
22parameter real threshold = 0.5;			// logic threshold level (V)
23parameter integer Start_Bit = 0;    	// defines if thermometer starts from 0 or 1
24
25real dout[2**`binary_bits-1:0];			// internal result variable
26integer code;
27genvar i;
28
29analog begin
30// convert binary input to code
31    code = 0;
32    for (i = 0; i < `binary_bits; i = i + 1) begin
33        @(cross(V(in[i]) - threshold))
34            ;
35        if (V(in[i]) > threshold)
36            code = code + (1 << i);
37            end
38//$display("Code = %d", code);
39
40case (Start_Bit)
41    0: begin	// Decimal 0 equals thermometer 0
42		for(i=1;i<2**`binary_bits+1;i=i+1) begin
43          		if(code!=i) begin
44              		dout[i-1]=vss;
45          		end
46      		else begin
47          		dout[i-1]=vdd;
48      		end
49		end
50	end 
51
52    1: begin	// Decimal 0 equals thermometer 1
53		for(i=0;i<2**`binary_bits;i=i+1) begin
54          		if(code!=i) begin
55              		dout[i]=vss;
56          		end
57      		else begin
58          		dout[i]=vdd;
59      		end
60		end
61	end
62endcase
63
64// Plotting outputs
65for (i=0; i<2**`binary_bits; i=i+1)
66	    V(out[i]) <+ transition(dout[i],0,0);
67end
68endmodule