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18 votes
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What is purpose of an Undervoltage Sensing Circuit?

I guess you are trying to understand why you need an IC to do what a simple transistor could do "in the old days", which is pulling a reset pin low (or high), right? If that's the case, a couple of ...
Lucas's user avatar
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7 votes
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Under-voltage lockout and a 555 (astable 50% duty cycle) lets LED flash – now save more power

At 50% duty cycle about an average 8mA is going into the LED and another 4.5mA is going into Ra. The TLC555 itself draws maybe another 0.6mA. That's 13mA * 60h = 780mAh. not so far from your 1200mAh ...
Spehro Pefhany's user avatar
6 votes

What is purpose of an Undervoltage Sensing Circuit?

From the product page at On Semi website. ."The MC33064/MC34064 is an undervoltage sensing circuit specifically designed for use as a reset controller in microprocessor-based systems."
vicatcu's user avatar
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6 votes
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Undervoltage lockout

This is the simplest circuit I can think of using BJTs that will provide under-voltage lockout. simulate this circuit – Schematic created using CircuitLab How it works: If Vin is higher than ...
Math Keeps Me Busy's user avatar
5 votes

What is purpose of an Undervoltage Sensing Circuit?

There is a bunch of voltage-sensitive activity inside a MCU, and not all activity has problems at the same (out of spec) VDD. A precise UVD ensures all the activities get the desired VDD, even tho ...
analogsystemsrf's user avatar
5 votes
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Powering 4 12V 0.45Amp fans off USB?

The piece of knowledge missing is the relationship between voltage, current and power, \$ P = VI \$. From this we can work out: One fan will require \$ P = VI = 12 \times 0.45 = 5.4 \; W \$. Four ...
Transistor's user avatar
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5 votes
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What is the maximum DOD for a Li-Ion Battery?

The lowest safe voltage for a lithium cell is around 3.0V irrespective of the capacity. Below this the cell will be damaged, but for longer life don’t discharge below 3.2V
Frog's user avatar
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4 votes

How bad is it to undervoltage a 12-volt lead-acid battery?

Answering to the question "Is there data available to quantify a loss in lead-acid battery quality from low-voltage events?" here are two good sources: "Battery life is directly related to how deep ...
ndemou's user avatar
  • 163
4 votes

What is purpose of an Undervoltage Sensing Circuit?

In a normal usage, the user will press the power button to turn a device off. When the MCU sense the button press, it will initiate shut down sequence and the firmware should set the pointer to the ...
Jason Han's user avatar
  • 1,780
3 votes

How to supply either 5V or 0V without the gradual PSU voltage bleed?

simulate this circuit – Schematic created using CircuitLab Figure 1. AC monitoring and shut-off. Monitor the AC instead. RLY1 will drop out when the AC is switched off. It's contact will open ...
Transistor's user avatar
  • 177k
3 votes

Lead-Acid battery discharged to 5V - how much damage?

When a battery sits for a length of time in a discharged state that's when the plates will suffer the most damage, the lower the voltage the worse it gets of course. if the discharge is very brief and ...
John Morgan's user avatar
3 votes

What is purpose of an Undervoltage Sensing Circuit?

Undervoltage situations can be bad for microcontrollers and memories. Many microcontrollers have a basic undervoltage protection system built in for this reason. The most common failure mode is ...
user's user avatar
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3 votes

Can the UVLO threshold be below the minimum supply voltage?

You are looking at two different bits of information. Both of which can be true. Minimum supply voltage is 8.7V. This is the lowest the input voltage can be where the performance of the IC is ...
Puffafish's user avatar
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2 votes

How bad is it to undervoltage a 12-volt lead-acid battery?

What normally kills brand new batteries fast is to have them discharge and leave them standing for weeks or months in depleted state. That is the typical fate for most "recreational" batteries. They ...
flodis's user avatar
  • 161
2 votes

How bad is it to undervoltage a 12-volt lead-acid battery?

I have experience with well over ten thousand batteries. Under Voltage batteries destroy the battery by causing sulfation in Lead Acid Batteries, or Dendrites in Lithium. Both are very destructive. ...
GreatBehoover's user avatar
2 votes
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Controlling BLDC with IR 2130 - stuck at fault, unable to reset

the /FAULT output is an open-drain output. You need an external pull-up resistor to your VCCIO logic supply voltage (3.3V or 5V). The open-drain output has a low-on resistance in the 55-75 Ohm range. ...
romain145's user avatar
  • 131
2 votes

Voltage Cutoff Circuit for battery based application

You will need an additional "switch" in series with the load circuit to disconnect the load. Q1 Cannot disconnect the load because of the manner in which it is connected in its present role. A P ...
Russell McMahon's user avatar
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2 votes

Circuit to protect against undervoltage?

You can connect a push/pull voltage detector (PMIC supervisor) such as the Microchip MCP112 or TC54 to a logic-level MOSFET, e.g. as described in the TC54 datasheet: (page 6) There are some popular ...
maxschlepzig's user avatar
2 votes
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Why does this LTC1440 Comparator switch so slowly?

You've only plotted four points on the curve (which are joined by straight lines). Try decreasing the increment in the DC sweep to 0.01 or something like that.
Spehro Pefhany's user avatar
2 votes

Should I add an undervoltage protection for lithium battery-powered projects?

It depends on whether you have a cell or a pack. A cell (usually referred to as a battery) is only the element itself. A pack contains a cell(s) but will have additional protection, usually ...
Cristobol Polychronopolis's user avatar
2 votes

How do ASIC designers approach designing for extremely low supply voltages like 0.3V?

I think you may have confused energy and power. One major component of power consumption in CMOS digital circuits is the power required to switch signal capacitance, and this power is proportional to \...
Elliot Alderson's user avatar
2 votes
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Implementing UVLO on battery charging and boost controller ICs

Is there a way to utilize LBO to build a UVLO ? with a transistor perhaps ? I don't think so. Reason: To be able to use LBI/LBO requires that the enable remains active all the time and, if enable is ...
Andy aka's user avatar
  • 465k
2 votes

Node voltage calculation

It would depend on the microcontroller output, how much current it can source and sink, if it's high, low or high impedance, how close to the supply rails it can go. If the controller was able to go ...
GodJihyo's user avatar
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2 votes
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Buck converter voltage drop and brownout

Straying from the recommended layout is begging for problems unless you know the effects of thermal and inductive properties of traces. Crosstalk and positive feedback leads to oscillations and ...
Tony Stewart EE75's user avatar
2 votes

Can the UVLO threshold be below the minimum supply voltage?

The UVLO threshold specification says that the device might not start at any voltage below 8.9 V. So in practice, your supply must be above 8.9 V. However, if your particular chip happens to start at ...
CL.'s user avatar
  • 19.6k
2 votes

Trying to fix leakage issue in this under-voltage cut-off circuit

Get rid of the 741 op amp and use an op amp whose output can go to near zero volts. As a result, Q2 is never completely off, resulting in Q1 never being completely off. Also, in simulation you can try ...
Marla's user avatar
  • 5,270
2 votes

Trying to fix leakage issue in this under-voltage cut-off circuit

The 1N750 is a 4.7V (nominal) zener diode. That's a bit too close to the 5V supply for even a rail-to-rail input op-amp, let alone a 741. The 741 cannot operate properly from 5V (10V minimum), the ...
Spehro Pefhany's user avatar
2 votes
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Can Li-ion BMSs be used with Li-po batteries?

Can Li-Ion BMSs be used with LiPo batteries? What you call a "LiPo" cell IS a Li-ion cell. It happens to be in a pouch, but it is still a Li-ion cell. Yes, that BMS will work, because the ...
Davide Andrea's user avatar
1 vote
Accepted

Lead-Acid battery discharged to 5V - how much damage?

Your battery has most likely lost some capacity. If this is a "car" battery, then it is probably significantly damaged. If it is a industrial battery with "deep cycle" capability, then it should be ...
Olin Lathrop's user avatar
1 vote

Voltage protection with 555 timer not working

The 555 Trigger input is dead-shorted to GND. Update 1: With the short removed, the Trigger input cannot be pulled low by the 675 output because the diodes are pointed the wrong way. The trigger ...
AnalogKid's user avatar
  • 21.4k

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