Anyone ever use the PIC12HV6xx family? - Page 1
Forum section: electronics / general

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2022, 07:14:47 pm
content: Looking at a new project that needs an 8 pin MCU and modest horsepower. I'm familiar with several varieties of PIC's but have never used the PIC12 flavor. Looking at the PIC12HV6xx for its 5V operation and A/D. Any pros or cons?Thanks!

author: JPortici
author_rank: Super Contributor
timestamp: February 24, 2022, 07:30:44 pm
content: The regular PIC12 runs at 5V.the PIC12HV has an integrated zener across VDD/VSS so you can power the chip from a higher voltage (just add a resistor between high voltage and VDD)IIRC the zener is 5V

author: jpanhalt
author_rank: Super Contributor
timestamp: February 24, 2022, 08:39:27 pm
content: Disadvantages?You are limited to the standard 14-bit core instruction set. The enhanced and later 14-bit instruction set (tables and indirect addressing are easier) and memory organization (e.g, linear, contiguous memory) have definite advantages. I would go enhanced midrange or later and take care of the voltage pre-MCU.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2022, 09:00:00 pm
content: Quote from: jpanhalt on February 24, 2022, 08:39:27 pmNormally I'd agree but for this application it's REALLY low level processing. Basically the MCU is just there to eliminate a handful of discrete digital and analog components. We prototyped this using an existing PIC18 board and the entire consumed program space was 539 bytes. Slower (20MHz) internal oscillator won't matter either.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2022, 09:04:20 pm
content: Quote from: JPortici on February 24, 2022, 07:30:44 pmEither the F or HV version would work for us. I only mentioned the HV because it's far more deeply stocked (at the moment!) with various distributors and mentioned its part number in case there are any problems folks have found with that specific version. Quick example: DigiKey has zero pieces of the F version but 10K+ of the HV version (both in SOIC packages). HV is in stock at Mouser and others too. Maybe the F is more popular...?Neither one has much stock at MicrochipDirect but they do have production coming in over the next couple of quarters.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 24, 2022, 09:23:05 pm
content: Quote from: IDEngineer on February 24, 2022, 09:00:00 pmYou asked for "disadvantages" of the 12HV6xx series. I presumed you were interested in speed and programmability. Apparently not. Give more information and get better answers.

author: mariush
author_rank: Super Contributor
timestamp: February 24, 2022, 09:30:09 pm
content: Have a look at PIC16F1521*https://www.digikey.com/en/products/detail/microchip-technology/PIC16F15213-E-P/12807187https://www.digikey.com/en/products/detail/microchip-technology/PIC16F15214-I-P/12807471If you don't mind it's not through hole, there's PIC16F1522x ... not hard to solderttsophttps://www.digikey.com/en/products/detail/microchip-technology/PIC16F15223-I-ST/12807539https://www.digikey.com/en/products/detail/microchip-technology/PIC16F15224-I-ST/12807184soichttps://www.digikey.com/en/products/detail/microchip-technology/PIC16F15225-I-SL/12807441

author: Ian.M
author_rank: Super Contributor
timestamp: February 24, 2022, 09:49:06 pm
content: You cannot use a PIC12HV6xx from an existing 5V supply rail. The internal shunt regulator is specced for operation between 4mA and 50mA (subject to total package dissipation limits) and direct connection to a 'stiff' 5V will destroy the PIC. Either power it from a regulated voltage <4.5V or from a current limited (<50mA) source with a compliance voltage over 5V. If a simple dropper resistor is used, from a supply that is not closely regulated, it needs significant 'headroom' for the variation of current with supply voltage to be small enough for the regulator as its acceptable range is likely to be further restricted by your application.AN1035contains some majestic kludges to work around this limitation!

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2022, 10:52:57 pm
content: Quote from: jpanhalt on February 24, 2022, 09:23:05 pmFair enough, though I did try to convey that in my OP with the phrase "modest horsepower".Better phrased: I'm wondering if anyone has had problems with this family, or reasons to avoid it. Ian.M's comment about the 5V supply is right on target, for example.Thanks!

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2022, 10:54:16 pm
content: Quote from: Ian.M on February 24, 2022, 09:49:06 pmWhoa, thanks for pointing this out.Exactlythe sort of tip I was hoping to learn. Downloading the appnote now!Edit: "Majestic" was very appropriate. The use of a shunt regulator is really quite clever for their use case (allowing external access to the regulated voltage) but... wow. I'm especially in awe of the idea to use the MCU's own I/O pins to manage the current draw in real time for the benefit of the internal shunt regulator. These are low pin count devices to start with!Edit2: Yeah, I have to agree that the HV part isn't the right way to go. We have a nice regulated 5V ready to use so kludging up a bunch of stuff to prevent overtemping the PIC is just dumb. I have to admit my attention was grabbed by the relatively high availability of this part and I hadn't dug into its details, especially noticing the shunt regulator. Thanks for pointing that out, saved me a lot of time reading a spec sheet that's ultimately a poor choice in this case.

author: Avelino Sampaio
author_rank: Frequent Contributor
timestamp: February 25, 2022, 07:10:04 am
content: HiThe LCSC has the PIC12F675 - 5k (DIP) and 365 (SOIC). The price is a little scary.https://lcsc.com/search?q=pic12f675

author: IDEngineer
author_rank: Super Contributor
timestamp: February 25, 2022, 07:27:35 am
content: The '615 is barely stocked at all.https://lcsc.com/mobile/products/MICROCHIP_471.html?keyword=Pic12f615

author: jpanhalt
author_rank: Super Contributor
timestamp: February 25, 2022, 09:13:33 am
content: DigiKey seems to have a good supply of 12Fxxx and later MCU's:https://www.digikey.com/en/products/filter/embedded-microcontrollers/685?s=N4IgTCBcDaIAoEkDCBGMAxEBdAvkAYou might want to avoid the 12F5xx as it is only a 12-bit core with a slightly smaller instruction set and lacks interrupts. What package do you need?

author: IDEngineer
author_rank: Super Contributor
timestamp: February 25, 2022, 05:32:25 pm
content: Quote from: jpanhalt on February 25, 2022, 09:13:33 amStrictly speaking, eight pins will do the job. 5V operation, A/D, internal oscillator, and some combination of Timers/CCP's to do minor time tracking. Probably don't need interrupts, just run the peripherals polled because it won't be really busy anyway.We'll have some extra room on the PCB so I may have it laid out with multiple MCU footprints to improve sourcing given today's conditions.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 25, 2022, 06:01:13 pm
content: By package, I meant DIP, SOIC, etc. All 12F MCU's have 8 pins. As a little trivia, the 16F505 is a 12F508 with 14 pins. It's still a 12-bit core.

author: hans
author_rank: Super Contributor
timestamp: February 27, 2022, 01:09:18 pm
content: Quote from: Ian.M on February 24, 2022, 09:49:06 pmPerhaps I'm misinterpreting the spirit ("majesty") of your comment, but aren't these basically the same limitations/characteristics of a zener circuit? Or even to LEDs. E.g. if you use a dropper resistor with only 0.5V drop for an LED, then a supply variation of 0.5V will (roughly) double the LED current. So in order to get a stable current regulation, the minimum voltage input must be high enough to not vary the current too much (e.g. a 9-60V input has a drop of 4-55V, which is a range of 13.75x... which is greater than the shunt current of 4-50mA -> 12.5x range).The biggest advantage of this PIC is that the excess voltage and power is dropped in a resistor, which is very cheap to get in a large voltage/power rating, opposed to a small voltage regulator. It also saves space by avoiding the zener diode on the board..However, that cheapness is also a disadvantage. Such a setup may waste a lot of power. Say we have a rectified mains application that needs to survive on 120Vdc-400Vdc input. Then the zener will draw roughly 13.3mA at 400Vdc (if 4mA at 120V), and so maximum quiescent power is 400V*13.3mA=5.3W(!) That very likely won't meet energy/power regulations in many area's.

author: Ian.M
author_rank: Super Contributor
timestamp: February 27, 2022, 03:10:16 pm
content: Yes, its equivalent to a shunt Zener regulator e.g. a 5.1v Zener in parallel to an ordinary PIC's Vdd and Vss pins. However the HV PIC is far more restrictive as you can't disconnect the internal 'Zener' and it shares a dissipation limit with the rest of the PIC's die. Use an ordinary PIC + a separate Zener (or other regulator) and you can pick one with dissipation suitable to handle shunting the max. load current and don't have to resort to AN1035 kludges.Its really only suited to Muntzed to the max high volume designs where quiescent current draw is not important.