Adjustable Vpp Voltage

By: Mats - 2006-09-27 17:54:57

For many EPROMs the Vpp should be 21.0 V or 25.0 V instead of 12.5 V. But a standard Willem is designed for only 2 different voltages, 5 V for Vcc and 12.5 V for Vpp when programming. But with a DC-DC converter the 12.5 V can be converted to 21.0 or 25.0 V. We did this with an MC34063A and could then without problem program both 2732 (25 V) and 2732A (21 V). The cost of the components was about 2-3 EURO.  These functions should be integrated in the next Willem programmer, this would strongly increase its usefulness.

According to EPROM manifacturers specification Vcc should also be raised to 6 V during programming for those EPROM that are programmed with 12.5 V Vpp.  Willem does not do this but it seems to work most of the times also with 5V. But to work optimally maybe also Vcc could be raised to 6 V programming  "12.5 V chips" !

Re: Adjustable Vpp Voltage

By: DL - 2006-09-27 19:52:57

Hi Mats,

Willem's programmers use step-down regulators for VPP and therefore require an appropriate power supply to be used.   Going with a switching regulator is more trouble than it's worth.   The Willem 4.5 comes stock with a VPP=12.5V option, but is easily modified to get 21 and 25V.   The 4.1 already has 12.5, 21, and 25V settings.

Switching regulators are more applicable to high power applications where the increased power consumption makes the increased efficiency, complexity, and switching noise a worthwhile compromise.   Inappropriate component selection has caused problems for some programmers for VPP=21 and 25V.

I have been recommending that people modify their programmers that use the step up regulator and replace it with a more trouble free step down regulator.

Regarding programming EPROMs at an elevated VCC.   I've been promoting this for quite some time.   It used to be generally accepted that if a device programmed and verified at VCC=5V, everything was fine.   I think word is getting out that this is not the same as saying the device was programmed reliably.   Since the programmer and program don't have the ability to change VCC under program control and the correct programming VCC is dependent on the algorithm (and possibly manufacturer), it's up to the User to do the right thing.

Regards,
Dennis

Re: Adjustable Vpp Voltage

By: shirsch - 2008-05-30 01:19:42

DL wrote on 09/27/06 at 19:52:57:
I have been recommending that people modify their programmers that use the step up regulator and replace it with a more trouble free step down regulator.


Are the details for this mod available anywhere?  I have a Sivava PCB4.5 and would be interested in implementing it.

Steve

Re: Adjustable Vpp Voltage

By: targa - 2008-06-05 11:09:43

Hi all,
I don't have a power supply. which one is correct ? I wonder whether it'll be an AC one because there are rectification diodes mounted ?!
Thanks,
/Tomas

Re: Adjustable Vpp Voltage

By: DL - 2008-06-06 04:58:18

Hi Tomas,

It depends on which programmer you have.  If it's a PCB3 variant, you need 10-12VDC @ 500mA.  Others require the input voltage to be 3-5VDC higher than the VPP you need @ 300mA.  PCB3 require higher current because step-up regulator draws ~300mA at VPP=25V.

All programmers will take an AC supply, but some programmers have a half wave rectifier and will need a certain polarity for DC.  Most seem to be center positive, but I know of at least one that's center negative.

HTH,
Dennis

Re: Adjustable Vpp Voltage

By: targa - 2008-06-06 21:27:49

Thanks a lot.

Any working linux SW out there ? it's not quite clear from the topics in this forum.

Otherwise I'll have to revive my old Win2k installation.
/To

Re: Adjustable Vpp Voltage

By: DL - 2008-06-07 02:01:47

Hi,
targa wrote on 06/06/08 at 21:27:49:
Any working linux SW out there ? it's not quite clear from the topics in this forum.
I recall a Member saying it ran under Wine.

HTH,
Dennis