40

I've worked on AVRs as well as ARM Cortex-M3/M4/R4-based MCUs. I think I can offer some general advice. This will assume you're programming in C, not assembly. The CPU is actually the easy part. The basic C data types will be different sizes, but you're using uint8/16/32_t anyway, right? :-) And now all integer types should be reasonably fast, with 32-bit (...


38

Yes, this is widely known. Anyone who has tested it knows that. The die manufacturers certainly know it. They don't specify LEDs for more than 5V reverse voltage because it would not measurably increase sales (ie. very few need that capability) and would require them to actually consider each LED type and what voltage it might withstand (maybe 12V for some,...


36

I've always been told that the reason for using letters or symbols in place of the decimal point is neither for international relations or variable names in code but for clarity in print. The issue being that when datasheets were typed up, or schematics drawn, and then copied/photocopied/faxed/etc the dot may get dropped. This issue obviously isn't such a ...


34

That's the new politically correct way of writing numbers that would normally have decimal points. Some parts of the world (Germany for example) use a comma to separate the integer and fraction digits. To avoid ambiguity in international situations, some people now put the letter for the units where the decimal point should be. So "3V3" really means 3.3 ...


33

I'm sorry @Passerby. I couldn't resist.


31

Its never safe to exceed the maximum ratings. Even operating at a point within the ratings can result in failures if for example the manufacturing process has drifted out of spec (I've had power transistors fail in a prototype run soak test, and the manufacturer admit to a fault). The further from the 'safe' region you operate, the higher the chance of ...


25

If you stand under a tree in a lightning storm and you survived, does that mean anything significant? This is somewhat like reverse biasing an LED > -5V. Graph , courtesy of This shows the sensitivity of LEDs in both reverse and forward bias exposed to ESD. Note below, that it is far more sensitive to the left when Vr goes below -5V (I could write a ...


25

This is your circuit drawn as a schematic to read for understanding rather than as a wiring diagram (which is more about getting everything connected and not so much for understanding it.) simulate this circuit – Schematic created using CircuitLab The idea illustrated in your diagram, where the LED and a current-limiting resistor are placed in series ...


24

"Volt per square root hertz". Noise has a power spectrum, and as you might expect the wider the spectrum the more noise you'll see. That's why the bandwidth is part of the equation. The easiest is to illustrate with the equation for thermal noise in a resistor: \$ \dfrac{v^2}{R} = 4kT\Delta f \$ where \$k\$ is Boltzmann's constant in joules per kelvin,...


24

I've never seen the ND suffix at Mouser, only at Digi-Key. According to a blog article at Skywired: In those days, the “-ND” suffix meant No Discount. Prominently displayed on the catalog front cover was a schedule of discount percentages, with better discounts for larger orders. Full reels of parts and certain expensive items had an “-ND” on their part ...


23

Generally, the primary specifications will be the same, but beware as the devil is in the details as noted by Olin. As an example, take the LM1117. Parts with the same base number are also made by On Semiconductor and AMS. Looking at the datasheets, TI has this to say on stability: The output capacitor is critical in maintaining regulator stability, ...


22

BSC means "Basic Spacing Between Centers". This is often used if the reference lines don't refer to a physical point or edge, like in the case of the pins: the reference is in the middle of the pin, instead of one of the edges. BSC SQ = BSC square, i.e. in both X and Y dimensions. The abbreviation BSC is misused in the case of the package outline, and ...


22

Look at chapter 5 under line regulation. For the 5V regulator at \$V_{IN} = 7 V\$, then you will typically see a \$3 mV\$ ripple with varying load, up to \$50 mV\$ worst case. At \$V_{IN} = 8 V\$ this reduces to \$1 mV\$ typical and \$25 mV\$ worst case. So you'll need at least \$2V\$ head room, but \$3V\$ has less ripple (which is better) Another ...


21

First let's do a quick number crunch: 6.528W/10W = 65% (of 10W) Referring to the datasheet: There is about a 165C rise in temp. Do not touch!. As for "Is it a safe temperature for the resistor?", refer to the next figure: I'll admit that the Derating Curve Graph kinda hurts my head. But, if you follow the 10W curve over to 25C (about room temperautre), ...


19

Exceeding absolute maximum ratings is a bad idea. In some very limited circumstances, carefully pushing something past the limits might be worth the risk. This might apply to one-off situations where you know, for example, that the temperature will always be below 25°C and you think you can get away with violating something else a bit as a result. It ...


19

It looks for all the world like an Atmel AT24C16B, a 16kbit two-wire serial EEPROM chip. In particular, page 14 of the datasheet has this diagram explaining the markings on the DIP version of the chip: Seal Year | Seal Week | | | |---|---|---|---|---|---|---|---| A T M L U ...


19

The CAN pins do not have fixed pin assignments. Instead you are able to select which of the "Remappable Pins" you wish to use (RP0 through RP15). If you refer to page 180 of the datasheet, specifically the table titled "REGISTER 11-16" (RPINR26: Peripheral Pin Select Input Register 26), it details the register used to select the CAN RX pin location (C1RXR). ...


17

I once came across an app note from Atmel (not TI, I know - still interesting) that condones such a construction... For zero-cross sensing on mains! To protect the device from voltages above VCC and below GND, the AVR has internal clamping diodes on the I/O pins (see Figure -1). The diodes are connected from the pins to VCC and GND and keep all input ...


16

They indicate data direction. Arrows pointing to the chip indicate that those pins are inputs and vice versa. Bidirectional arrows indicate they are either inputs/outputs, depending on the circumstances. If you want to memorize it, I think you should memorize those pins meanings first.


16

The switch is available in Gold (Au) and Silver (Ag) alloy. Gold allows switching of low voltage and current signals, such as measurements. Silver allows switching of high voltage and current, such as power and coils. This difference is because the contact material degrades over time and per switching action, and a low voltage might not be able to get any ...


15

Ask Olin :-) - but wear a flame suit. Unlike data sheets, which SHOULD be holy writ (but often don't quite make it), Application Notes are a very "mixed bag". It does not pay to just take what is in an AN as gospel, although you'd hope it was at least usable without magic smoke. The following is opinion (of course). people are most welcome to offer ...


15

The leakage spec- in this case 0.01CV (or 3\$\mu\$A) is the product of rated voltage and rated capacitance, not applied voltage. The 3\$\mu\$A, of course, means "whichever is higher" (aka "worse"). So if your cap is rated at 10V/100\$\mu\$F, leakage would be less than 10\$\mu\$A. SP's rule #1 of data sheet interpretation is: If a spec can be interpreted ...


15

So, short story is the definition of absolute maximum rating does vary from manufacturer to manufacturer. Most every manufacture (of those sampled) will give a variation of this warning: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Then proceed to tell you that this might happen over time: ...


14

At the top of the chart it says "Vcc +- 15V." Then it gives the maximum output values Vom as +- 13.5V. So, it does not have rail to rail output. Then look at Vicr. That's common mode input voltage range. Typical is +-11V when operated on +-15V. So, input is not rail to rail.


14

\$V_{EB}=V_E-V_B\$. The datasheet is saying the emitter can be (up to) 6 V above the base, not that the base can be 6 V above the emitter. With \$V_{BE}\$ (\$V_B-V_E\$) at 6 V, an absurdly large current will flow into the base and burn out your transistor very quickly.


14

In the datasheet of any PIC there are registers and each bit of those registers are showed and explained. But in the datasheet of STM32 chips I could not find any registers. How can I find all registers in STM32 chips and specific bits of these register. The Datasheet contains the external description of the MCU, i.e. pin mappings, electrical ...


13

No, using one manufacturer's datasheet to get specs on another manufacturer's part is not a good idea, even for common parts like a 1N4148. In this case, there should be the minimum specs somewhere for what a 1N4148 must do, but individual manufacturers may exceed those. You can only count on the minimum specified in the generic 1N4148 definition when ...


13

You are looking at the datasheet. It is not there. It is in the reference manual. For STM32, datasheet is mostly for package specific things like pinouts and electrical specifications (that's the only time I ever look at it anyways). User reference manual is for device common things like registers and peripherals which is almost everything else.


12

NOM = Nominal, that's the value you normally can expect, and what the device is designed to. Note that nominal values are often not the best to calculate with. If you want to go worst case you'll have to calculate with Minimum or Maximum, depending on the parameter and the application.


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