16F88 vs. 16LF88?

[Hank Fletcher]

What's the difference between the PIC 16F88 and the 16LF88? I've been looking at the datasheet, but could only find the part in reference to the 16LF87 as having an extended supply range. Is the 16LF88 just have a lower supply voltage feature? Can anyone point me to where in the datasheet it describes this? Sorry for the noob question, I just want to know if I can pretend that a 16LF88 is a 16F88. Thanks!

 

[bananasiong]

Yes, LF has the lower supply. The programming method for both of them are still the same. I think they have different working temperature range.s

 

[Hank Fletcher]

By lower do you mean that it can be operated lower, or that it must be operated on a lower supply? That's what I was looking for the specifics of. It's just that the store I was going to buy it from has the 16LF88 but not the 16F88. I'm trying to keep things simple because this will be my first time with a mcu - my preference is to keep everything at 5V supply (other than the motors, but that's another story).

 

[bananasiong]

It can be operated in lower power. You can see the graph showing their different range of supply voltage, under electrical characteristics in the datasheet.

 

[upand_at_them]

Section 18.1, DC Characteristics, Supply Voltage (page 165):

16LF88: 2.0-5.5V
16F88: 4.0-5.5V

 

[Hank Fletcher]

That's what I was looking for! Thanks both!

 

[donniedj]

The device MAY be operated on a lower supply. Look at the table for Supply Voltage, should the first couple of the DC Characteristics at the bottom of the datasheet. LF has a 2.0v to 5.5v range and F a 4.0v to 5.5v range.

This place is getting too slow. I posted as #4 and ended up as #7. Not only do I look like i repeated what someone else wrote, I ended up posting for no reason because answer already exist!

 

[Pommie]

You should also be aware that the LF has a maximum operating frequency of 10MHz.

Mike.

 

[Hank Fletcher]

You should also be aware that the LF has a maximum operating frequency of 10MHz.

Mike.

I hadn't seen that yet! Is that definitey the top end, even if you're running it at 5V?

 

[eblc1388]

I hadn't seen that yet! Is that definitey the top end, even if you're running it at 5V?

Yes, 10MHz maximum even at +5V.

If the LF part can operate at the same frequency range as the non-LF part but also comes with a wider range of operating voltage, no one would buy the regular part but all get the LF part instead.

I think you would.

 

[3v0]

PIC16F88
Oscillators:
• Three Crystal modes:
- LP, XT, HS: up to 20 MHz
• Two External RC modes
• One External Clock mode:
- ECIO: up to 20 MHz
• Internal oscillator block:
- 8 user selectable frequencies: 31 kHz,
125 kHz, 250 kHz, 500 kHz, 1 MHz, 2 MHz,
4 MHz, 8 MHz

 

[justDIY]

refer to pg 164 of the 16f88 datasheet, figure 18-2:

2: FMAX has a maximum frequency of 10 MHz.

I'd hazard a guess most applications implementing the LF version of a chip will be using its internal osc, so the higher speed is nothing but wasted capacity in that regard.

 

[Pommie]

PIC16F88
Oscillators:
• Three Crystal modes:
- LP, XT, HS: up to 20 MHz
• Two External RC modes
• One External Clock mode:
- ECIO: up to 20 MHz
• Internal oscillator block:
- 8 user selectable frequencies: 31 kHz,
125 kHz, 250 kHz, 500 kHz, 1 MHz, 2 MHz,
4 MHz, 8 MHz

What was the point of quoting datasheets. It doesn't even mention any fact that is relevant! Your post suggests that the LF can run at 20mhZ. I posted earlier that the LF has an upper limit of 10MHz.

Please explain what you didn't understand about my earlier post. Or, why you think quoting the data sheet is relevant.

Mike.

 

[Nigel Goodwin]

Your post suggests that the LF can run at 20mhZ. I posted earlier that the LF has an upper limit of 10MHz.

As with all PIC's, the stated maximum isn't a 'limit', just an advisory value. But generally if you're using a low voltage supply it's to reduce current consumption (amongst other things), and running at a lower frequency drastically reduces consumption.

I'd be surprised if a 16LF88 won't actually work at 20MHz, but is the OP even wanting to do this? - mostly you can run far lower clock speeds.

 

[Hank Fletcher]

If the LF part can operate at the same frequency range as the non-LF part but also comes with a wider range of operating voltage, no one would buy the regular part but all get the LF part instead.

That's really what I was looking for: what the trade-off was for having a PIC that was essentially the same as the 16F88 in every respect but had a greater supply voltage range. I'm guessing 10MHz will be plenty fast enough for my project, and if I can run it at 5V anyway, that's one less thing I have to think about.

 

[Nigel Goodwin]

That's really what I was looking for: what the trade-off was for having a PIC that was essentially the same as the 16F88 in every respect but had a greater supply voltage range. I'm guessing 10MHz will be plenty fast enough for my project, and if I can run it at 5V anyway, that's one less thing I have to think about.

What is your project?, often running at 4MHz is many, many times faster than needed.

 

[Hank Fletcher]

It's the trombone robot I was going on about a couple months back. I recently posted some photos in another thread where I started looking for some encoder information:
https://www.electro-tech-online.com/threads/rotary-encoder-sales-site.30762/
Like I said there, I have a short video that perhaps better illustrates the movement of the slide, but I don't think I can post a <1MB .avi.

I've also started another project recently which will hopefully be finished by the end of the summer. This will be an autonomous recorder, and will run off the PIC 16F88 (or 16LF88, as it's shaping up to be) also. I don't doubt that for both projects the PIC's processing speed will be plenty fast enough, it's more of a question of whether the 16LF88 will have enough I/O pins for both control and feedback in either project. For instance, in the case of the trombone robot I thought it'd be nice to have a three digit LED display indicating the slide position measurement at any given time (so I'm thinking ten output pins for 10-bit parallel output, unless someone can clue me in on how to do that serially).

In the case of the recorder, I'm planning on using one output pin per solenoid "finger." For the first crack at the recorder project I'll need at least eight solenoids for the fingers (it'll just play at a beginner recorder level: range of one octave and a minor third, only plays in keys of C, F, and G major - i.e. no half-holing). And then another solenoid (or something) to control the articulation (tonguing) of the notes. Not to mention some means of control over the wind production!

If you've read this far, you've no doubt figured out that I'm new to the world of PICs. I'm sure there's a better choice than the 16LF88 for these applications, but given that I'll be working up the learning curve of PICs this summer, I figure I'll cross the bridge to a better PIC when the time comes, which will be after I've learned how to use the most common of PICs.

 

[3v0]

What was the point of quoting datasheets...

Sorry Mike. Must have had my shirt on backwards. That is to say I misread one of the other posts. It makes no sense at all.

 

[Nigel Goodwin]

In that case speed is the least of your problems, you could probably run at only tens of kilohertz and still be more than fast enough - anything mechanical is SLOWWWWWWWWW!.

 

[Hank Fletcher]

...you could probably run at only tens of kilohertz and still be more than fast enough - anything mechanical is SLOWWWWWWWWW!.

I get your point, but 10K might be exaggerating (i.e. under) a bit. The goal for the speed of the trombone robot was to have it capable of moving the slide as fast and as accurately as a professional trombone player. That means moving the slide between any consecutive semitones with a rhythm of sixteenth notes at a tempo of 150bpm. And that's just moving the slide, not stopping it for notes! So already we're talking on the scale of 1KHz, and we haven't even taken into account the time it will take to calculate for PID at any given moment in any given situation (i.e. how fast, how far, for how long the slide is moving), or the programming that will eventually be required to coordinate the slide movement with air and articulation in the rest of the robot.

Mechanical movement is slow, but not when it comes to emulating the capabilities of the human body. Do I really need to explain that to a Martial Artist?