TinyCPLD

[Mariss Freimanis]

I've started this thread to continue where it left off regarding a CPLD solution for problems encountered using the A3986 on the "New Allegro Bipolar Stepper Driver A3986" thread in this forum.

Mariss

[Mariss Freimanis]

(Moved from previous thread)
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"Mariss,
Two questions :
1. Regarding cpld firmware, do you plan to implement on it any kind of midband resonance compensation ?
2. Following the thread topic : would you like to "coach" a team to develop an open source board (without any fancy characteristics) ? I mean that I would be more interested to make such a board rather than trying to sell kits.

Regards,
Daniel
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1) No. (a) Other single-chip solutions don't offer it, (b) it would directly conflict with our commercial products. I'm looking at the CPLD solution to provide what other application specific ICs promise but don't quite deliver; an IC specifically designed (programmed) to provide a well behaved CNC-rated drive.

2) In essence that is already accomplished. The CPLD circuit design governs what the external support circuit has to look like. The bridge design is more open to a "roll your own" approach as is the STP/DIR interface (optos, no optos, etc.). Current set is the same as well; provide the circuit with a 0 to 3.3V range reference and you get 0A to 7A output current range.

Mariss

[tivoidethuong]

To Mariss
In your Tiny CPLD schematic, How 12V regulator work?

thanks you

[tivoidethuong]

To Mariss

I see in xilinx XC2C32 was discont product

[joshua221]

Mariss,

In the previous A3986 thread you mentioned that chopper circuits were 70's tech. What is the alternative?

[pminmo]

Originally Posted by tivoidethuong To Mariss I see in xilinx XC2C32 was discont product

not the a version.

[pminmo]

Maris,
I'm curious about the 1.8V led supply. The cpld is rated 2V max. I've seen LED's go as high as 2V, and the 1st three I looked up, specd 2.1 to 2.4V max. Is there a specific led your comfortable with that meets the 1.7 to 1.9V spec?

[Mariss Freimanis]

LED voltage depends on color; green will be over 2V, infrared will be under 1.5V and GaAs red is 1.8V at 4mA in an 0603 package. The tempco is -2mV/C giving a 100C operating range from 1.7V to 1.9V. The CPLD consumes microamps at 5MHz so a shunt regulator is dandy.

Mariss

[Mariss Freimanis]

joshua221,

The PWM circuit I have presented.

Mariss

[Mariss Freimanis]

tivoidethuong,

The MOSFET is turned 'on' by the drain to gate resistor. As it turns on, the voltage rises until the 12V zener conducts. As it conducts, it begins to turn on the NPN. The collector of the NPN works by decreasing the MOSFET gate voltage and therefore the output voltage. Emitter degeneration is used to limit gain to keep the circuit stable, the 33 Ohm resistor in the source path is designed to burn open should the 12VDC load exceed 60mA. This protects the regulator against short-circuit damage.

Mariss

[hab82]

Are we trying to hide the purpose of this device. The title of the thread means something only to those people who read the end of the A3986 thread. Also the function schematic and layout still exist on that thread with no pointers from here. Could we extend the title to indicate the purpose of the TinyCPLD. It might catch much more interest so we could indeed justify the programing of >100 of these devices. By the way how are we coming on a potential purchase date etc. I believe I have seen about 5 offers to purchase at least 10 of the devices with some expression that even more would be of interest.

Hubert

[MrWild]

Think outside the box. The problem Mariss is addressing is to a whole slew of drive questions across several threads. One person asked if they could change some parts on the 250/251 and up the voltage and or amps. Another person asked if the 201s could be upped to 10 or 12 amps. Mariss is giving something valuable for just $5 (when bought by the 100 piece lot) This is the ability to take this device and make as high a power stepper driver as you care to get silly with.

Mariss is giving a a slightly dumbed down version of the brain that makes his drives so good. Mid band damping? You'll need mechanical dampers, but you get PWM, not chopper. Not a bad trade off.