d. High programming voltage adapter for Super speed microcontroller programmer
Vhigh = 1.25 V ( 1 + R2 / R1 ) + IAdj R2
Vddprg = 1.25 V ( 1 + R4 / R3 ) + IAdj R4
IAdj is regulated by LM317 to be below 0,1 mA. To get the Vhigh and Vddprg voltages into desired ranges: Vhigh = 8 V .. 10 V and Vddprg = 3.3 V .. 5 V you have first to decide on the values of R1 and R3. You may go for 680 ohms that you have already used for 3.3 V regulators. Now, we can calculate R2 and R4. It is important to meet as many PIC18 programming datasheets requirements as possible. Therefore we can go for: Vhigh = 8.4 V and Vddprg = 4 V. It works perfectly with PIC18Fxxxx and PIC18FxxKxx microcontrollers!
R2 = (Vhigh– 1.25 V) / (1.25 V / R1 + IAdj)
If you have already built a low voltage programmer, you just have to add a high programming voltage microcontroller programmer adapter and a 12 V power supply to enable high voltage programming. You also need a new vesrion of programming application. Go to Downloads section to get 32-bit or 64-bit PIC programmer v2.9.9 (x64) application. The adapter enables you to program PIC18Fxxxx and PIC18FxxKxx microcontroller families. PIC Programmer application currently supports PIC18FxxJxx and PIC18Fxxxx microcontrollers. Two examples are shown on the schematic below: PIC18F2550 and PIC18F4550. Both microcontrollers can be programmers with PIC programmer v2.9.9 (x64) application.
Resistors R1 through R4 values have to be calculated to meet the required voltage ranges. You may also decide to use trimmers (variable resistors). Here are the instructions for resistors values calculations:
R2 = (8.4 V – 1.25 V) / (1.25 / 680 A + 0.1 mA) = 7.15 V / 1.938 mA = 3,69 k ohms
R4 = (Vhigh– 1.25 V) / (1.25 V / R3 + IAdj)
R4 = (4 V – 1.25 V) / (1.25 / 680 A + 0.1 mA) =3.75 V / 1.938 mA = 1,42 k ohms
SEE THE SCHEMATIC BELOW:
The basic low voltage PIC programmer on the left is connected to the high voltage programming adapter on the right. Click on the photo to enlarge it.
NOTE: If you decide to use a trimmer in place of R2, it should have 5 k ohms (or 10 k ohms) of maximum resistance. If you go for 10 k ohms trimmer, you will have to set it to less than ½ of full range.
If you decide to use a trimmer in place of R4, it should have 2 k ohms of maximum resistance (or 1 k ohms, if you add a 1 k ohms resistor in series).
ALSO READ: Super speed programmer schematic.
Click on the shematic to enlarge it.
PIC18 programmer with the high voltage programming adapter attached schematic. Click on the picture to enlarge it.