# Tag Info

6

Short answer: You are absolutely right not to worry about the smaller pullup resistors, since your bus will be in a high state the vast majority of the time. Moreover, the slow rise times will probably increase the power consumption significantly. Just use the 2.4kΩ resistors. Long Answer Very slow edge rates will actually cause CMOS inputs to consume ...

6

The datasheet for a specific part is the law. Some parts in the LVC family were designed specifically to interface between different supply voltage levels, and their specifications will be different than standard logic chips. Your links are to entire manuals so it's difficult to figure out exactly which specifications you are talking about. The "absolute ...

6

You need a wheel. A bicycle wheel should work, and the flashing light makes sense on a bike. Some other wheel may work, depending on what do you have at hand. Maybe a fan would work. Buy a magnet and reed contact like these. Connect battery, LED, resistor and the reed contact in place of the switch. Now just approach the magnet to the reed contact, it ...

5

but won't be more efficent to just cut de power with a transistor controlled by the MCU? Start looking at the datasheet! If standby mode consumes no more power than the leakage of your FET, then the FET is pointless. There's probably no leverage to be had here because of your 1-day interval, but a GPS receiver takes time to lock on to enough satellites to ...

4

There are two kinds of power losses in a chip: static (leakage) dynamic (switching) Voltage scaling reduces both power losses as a square of the voltage so the benefit of reduced voltage is substantial, especially for a mobile device where battery life is king. There is a trade off however. Generally, a lower voltage results in a longer switching time ...

4

LVC stands for "Low-Voltage CMOS"; this family was originally not designed to work with a 5 V power supply. LVC1G/2G/3G devices are newer and have additional features: not only full 5 V capability, but also support for partial power-down, i.e., when VCC = 0 V, all I/Os are allowed to be pulled high. (For those devices, see newer manuals like How to Select ...

3

It is generally a diode OR circuit, a diode from the battery and a diode from the solar panel, when ever the solar panel has enough light, its voltage is higher than the batteries, so it stops it discharging and runs off only the panel, the earlier devices would also have a shunt regulator to keep the maximum solar panel voltage from getting too high, A ...

3

as your micro controller is only drawing such a tiny amount of power, an LDO with a low quiescent current, ideally lower than your microcontroller, will likely end up more efficient, most inductor based switching converters struggle at very low loads, e.g. the LDO you linked draws 15uA at idle, so your power wasted is (the supply current of your micro * ...

3

Can I expect the RC oscillator to draw even less current than crystal one? You can expect nothing. However, a guideline to reading datasheets that I rather disdained when I heard it from an old guy with bushy white eyebrows 35 years ago, and which I've come to believe solidly since, is that if the parameter isn't mentioned in the datasheet, it's because ...

3

CC1101 radio should consume 0.5 µA when in Wake on Radio (WOR) sleep mode. See section 4.1 of the datasheet. Thanks to Chris Stratton I realized that I missed the radio needs to periodically wake up, which makes CC2500 to consume depending on conditions 6.3 µA to 544.5 µA, see Current Consumption for a Polling Receiver.

3

Put an impedance converter (voltage follower) at the output of the low pass filter. This will have high input impedance and deliver your 10mA at the ouput.

3

Indeed a normally closed switch means that a current must flow otherwise you cannot detect when the switch opens (and there is no more current flow). Fortunately there are several ways to minimize the current consumption. The simplest way is to use a very high value pull-up (or pull down if you prefer) resistor, a value of a couple of Mega-ohms will reduce ...

3

You need to work out a power management strategy: Will each circuit be powered all the time? Can the MCU be put in power-save modes and if so, how often? Should you use extra components to power off power-hungry parts completely? For example, you might be able to only power the RTC and wire it up to power up the voltage regulator at the right times, for a ...

3

Because you've done some adequate research into a solution and have put together a half decent requirement I'm making an answer... The ADG819 2:1 multiplexer operates from 1.8 volts to 5.5 volts and has a maximum D-S leakage current of +/- 10 nA across the full -40 C to +125 C temperature range. On-resistance is 0.8 ohms maximum and this would result in a ...

3

Regarding the latter, how can the CPU enter sleep mode and keep the OS running? I am open to any suggestions. You use co-processors. Phones are doing this for years now. They have one or more big ARM Cortex-A cores for the *unix based operating system. And one or more smaller ARM Cortex-M like processors for the background stuff. Like counting your steps ...

3

The datasheet is providing a promise that 10 uA is the worst-case (non-switching) current across the -40 to +85 degC temperature range. As you mention, there are hints both in semiconductor physics and elsewhere in the datasheet that the high temperature condition is likely to be critical for power usage. Notice that as the temperature range extends upwards (...

3

In active mode the current consumption of the ICs are around 20 mA and according to the datasheet the efficiency of MAX640 is around 90 %. Hence the total current consumption will be around (20 mA/ 90 %) = 22-23 mA, right? No, that doesn't make any sense. Look at the graphs in the data sheet typically this one: - With a load current of 20 mA (not ...

3

There are LDOs available for that purpose. Some examples, I know of: - NCP785A, NCP786A from On Semiconductor - TPS7A78 from Texas Instruments - LR8 from Microchip The devices from On Semi for example only need a diode and two caps to deliver 10mA of stabilized power at the rated voltage, eg. 3.3V, 5V, 12V, 15V, directly from the mains with 85VAC to 260VAC ...

2

A circuit diagram of ALL the components involved is always a good idea. If you have told us about ALL the components the diagram will be simple and easy. However, OFTEN we find there is "stuff" not mentioned. The term "comparator window" suggests hysteresis but this may not be what you mean. Just moving the window is unlikely to be a vast help - except if ...

2

There may be problems if you have unpowered peripheral devices connected to a powered microcontroller. You need to make sure that all microcontroller pins that are connected to these peripherals are set to a low voltage (logic 0) before removing power to the peripherals. Otherwise, significant current will flow through the input protection circuits of the ...

2

I have a little device which is normally powered by 5V 2A. But the manufacturer says it is compatible up to 16V 2A and I tested it with a powerbank which outputs 12V 2A. Will I be fine with simply connecting the battery to the device and it will self regulate the Ampere? The maximum output voltage of a LiPo is 4.2V/cell or 12.6V for 3 cells in series ...

2

@rdtsc has removed his answer which IMO raises a valid concern. I don't think the OP can rely on +5V to always be present (else, they wouldn't need the battery, would they?), and when that +5V is removed, the MCU will be powered via the pin's clamping diodes. It is therefore recommended to either add a significant series resistor to the measurement pin ...

2

A 32 bit timer at 32768 Hz will give you that kind of time period (up to 36 hours.) Maybe a Silego GPAK3 could do it. It has logic, counters and an internal clock reference that together could make that long of a resettable timeout. In volume they’re about 15 - 20 cents. And they’re really small.

2

As mentioned above, mosfets have leakage currents that might be in the same range as your minimum current requirements. The blocking mosfets have a Drain-to-Source Leakage Current and the conducting mosfets will have a Gate-to-Source Leakage Current. If these issues can be tackled, then your suggested circuit will work nicely. Therefore: search internet ...

2

The circuit simulator isn't working for me today (grr). PNP. Emitter to +V, base to RTC through a resistor (100k$\Omega$?). Collector to boost converter, with resistor to ground (same as base resistor). Size the resistor for a happy medium between turning on & off reliably, and not consuming too much current. It should consume very little current ...

2

Adding a capacitor bank will defintely help in sharing the peak current load, but super caps especially have higher significant internal self discharge and also significant ESRs. Below sample datasheet is from ELNA Here I have worked out a simple example to find the right value of the capacitance needed: Requirements: 1. Voltage should not drop by ...

2

Updating from new question's comments, Image Source: http://ultran.ru/sites/default/files/catalog/svetodiody/brend/datasheets/er18505.pdf You're ER18505 lithium cell looks to have an ESR of about 4 $\Omega$ for most of its discharge curve, , you're drawing surges up to 200mA for 100 milliseconds Based on what you have given, you can expect a voltage ...

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I will try to answer 1. Aesthetics: Please never draw a schematics like this. I wish your second schematics will be nicer one. The ground should always be in the bottom and the supply should always be on the top. Poor drawing simply sets off readers because it is so difficult to comprehend and needless to say it doesn't look good. You should really ...

2

The letter of the I2C spec says that the powered-down device is not supposed to drag down the I2C lines. In practice, this may not be the case, depending on how the chip designer implemented their I2C I/O pads. I2C is supposed to be open-drain. However, sometimes designers will use a 'pseudo-open-drain', that is, a regular I/O pad that's wired to use output ...

2

Each manufacturer of a battery chemistry category will try and evaluate the temperature behavior of their commercial technologies, because doing so may give them a new market worth pursuing. (Or let them know which markets NOT to pursue.) Some battery types don't even work until the temperature is over $60^\circ\text{C}$. While that might seem bad, it's ...

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