Questions tagged [ldo]

A Low Drop-Out or LDO regulator is a DC linear voltage regulator which can operate with a very small input–output differential voltage.

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Stepping down DC-DC 24v to 5v using LDO [closed]

Newbie question. I was wondering if its possible to step down dc-dc from 24v to 5v using a LDO or do I have to use a buck converter. Max current (peak value) will be 400mA, with continuous 100mA. ...
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TV Hisense HLE4815RT not tuning cable signal

I have a Hisense TV HLE4815RT (mainboard: RSAG7.820.5649), that suddenly stopped tuning cable signal, it just says "No signal". I tried different cables, removing some splitter, ...
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Need help identifying this ldo pinlayout

I have this regulator in sot package measures 4.5mm x 2.5mm xy, The layout is 1-out, 2-in(together with the undersidepin), 3- ground. I believe this is a 3.8v regulator, i want to find a compatible 3....
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Linear Regulator: What is Current - Supply (max)?

I am using an LDO to step 3.0V from a battery down to 2.8V, and I am trying to figure out what the "Current - Supply (max)" parameter means. Is it how much current can be supplied to the IC ...
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Should I use a DC-DC converter or an LDO?

In my project, I am designing a board which is supplied by a battery. The battery is a LiPo, 3.7 V, 1000 mAh, so its voltage range is 3 - 4.2 V. All the components on the board need a fixed voltage of ...
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Identification IC: LDO, SOT23-5, Marking HR1zG

I am searching for a few days now for what is presumably a LDO. The package is SOT23-5, marking HR1zG (or with a bit of fantasy HR1z6) ...
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LDO units for noise [duplicate]

In this Link, on page 6,they have mentioned the LDO noise in terms of uV/(sqrt)Hz. Can someone tell me what does this unit mean and how to understand this unit?
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Is it better if each integrated circuit has a dedicated voltage regulator?

I have a circuit consisting of an ESP32 microcontroller and some integrated circuits. Is it better if each integrated circuit has its own voltage regulator? Example: Full circuit after modification :...
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FoldBack Desing [duplicate]

I'm having a problem designing a foldback. I need it to have an opamp and a transistor. The problem is that the models I've been looking at don't work. I have to fulfill that for Imax=1.5 amp, go to 0....
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3 votes
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373 views

Open ended LM2937-5 outputs 12V

The LDO, LM2937-5, with 12V input voltage and nothing connected to the output terminal, outputs 12 V (measuring using voltmeter). As soon as I connected 100 uF capacitor, it shows 5V. Datasheet ...
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STM32 Low Quescient Current Power Supply

I want to find the most efficient way to power an STM32 microcontroller from a lipo (3.7V nominal). I have calculated that @ 3.3V, the current consumption is approximately: in run mode:1.75mA in idle ...
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LDO not improving power supply noise

I'm trying to create a low-noise 3.3V power supply to power an ADC. The TI TPS7A53 LDO seems like a good option for this. It has low noise of 4.4 μVRMS and a worst-...
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LDO PSRR Value Problem

I am searching a LDO for my design but I have a problem. Some of the LDOs don't have PSRR value. So, I can not compare these LDOs then others for noise feature. For example here are 2 LDO. Why these ...
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+12V main voltage tolerance as power input for an industrial PC motherboard

Regarding the following circuit, we have two main devices: MAX8792 Step-Down Controller. LT3065 LDO. I want to know the minimal "+12_Main" voltage that can be applied and still make this ...
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How to limit voltage to equal or less than 6 volts for MCP1826 Vin?

Voltage from solar panel could exceed the 6 volt maximum Vin specification of the MCP1826-3302 LDO. How can voltage be kept below Vin maximum specification? MCP1826 datasheet How should the PWRGD pin ...
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Switching off an LDO to avoid damages?

Say I'm using an LDO to power an MCU such as the ATmega328p with 3.3V from 3 NiMH AA batteries. What it isn't clear to me how to deal with brown-out situations. I can think of 2 possible risks (i.e. ...
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LDO not working correctly

I am making a custom PCB for an ESP32-S2 chip and the LDO controller is returning me 1.88 V instead of 3 V. Of course this is not enough for the ESP, but no matter what I do I can't get it to work. At ...
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12v to 5v + 3.3v regulation capacitors help

I am using a K7805 buck converter module to drop 12v down to 5v, with a ceramic capacitor on the input and output as per the datasheet. Directly after this i have am AMS1117-3.3 to give me the 3.3v ...
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103 views

Can you place a large series resistor on the input of an LDO?

I would like to use an RC filter to filter out noise, since the down stream components only needs a maximum of 30mA. Is it possible to use such a large resistor on the RC filter to achieve very low ...
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PCB Layout - Option to power from LDOs or benchtop PSU

I have a problem where I would like to have 2 options for powering my board - via multiple LDOs or via a benchtop DC power supply with one output. The issue is that there are four HPAs each consuming ...
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Supporting different voltage power bricks

I'm designing a simple PCB that will control some sensors/actuators with a microcontroller. The microcontroller requires 3.3V and I'm planning to support different types of sensors/actuators that can ...
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Adjustable LDO's - Voltage Input, Output, & Potentiometer Use

I am looking to use an LDO with a negative adjustable output voltage. I have found two products sold by TI that have similar schemes for setting the output through external resistors. I am slightly ...
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Does voltage drop resistor affect power dissipation?

I need to power an RFID from 24 V DC voltage. The RFID requires max. 9 V and max. 120 mA. The RFID suggests a 7809 linear voltage regulator. I thought too much and I want to use a 7809 because if I ...
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LM27762: 200 mV difference between positive and negative

I'm trying to figure out why there is 200 mV difference between positive and negative voltage on LM27762 (measured these values at op-amp pins). I used a schematic from their datasheet and everything ...
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DC resistance on soldered PCB between power and ground

I have just finished soldering a PCB I made with a couple of components (Spartan 3e FPGA), and I was checking the DC resistance between my power rails and GND to make sure they were not shorted. I ...
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Is this an acceptable way to create +/-5V from +/-12V?

The TLV76750 is a 5 V fixed-voltage LDO. I plan to use it to create ±5 V from ±12 V. Is there any caveat in hooking two of them up as shown below? The setup at the top is the standard configuration. ...
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LDO Outputs wrong voltage

I am working with a very low profile LDO, TCR5RG18A and I'm having issues at the regulators output. It's outputting 0.9V which is half its nominated value (nominal value = 1.8V) The LDO is operated at ...
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14 votes
4 answers
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What is the difference between a linear regulator and an LDO

Can someone tell me what the difference between linear regulators and LDOs is? From what I have read and understood, it is that linear regulators and LDOs don't use switching elements, but I think ...
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Minimise voltage drop during switching between external power supply and USB power for uC

When I want to use 5V from a LDO as the regular main power supply for my circuit and only want to switch to 5V USB from the USB connector when no external 5V from the LDO are recognised, I could do ...
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Why is it suggested to power XOs with LDOs?

I've read in various places that crystal oscillator ICs require very clean power (as opposed e.g. to your usual 3.3V rail from some switching regulator) and one way to achieve that was via LDOs. (Ref1)...
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Calculating the Input Current of the LDO

I have an LDO with output specification of 1.8V and 0.45A of load current. Input voltage is 3.3V. To find out the input current, is my below calculation correct? Input Current = (1.8V * 0.45A) / 3.3V =...
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Wrong voltage out of ST LE33: 1V instead of 3.3V

I got an ST LE33 and I am providing +5V between pin 2 and pin 3 as per specs. Checked with a multimeter. I am reading +1V between pin 1 and pin 2, without any load, no capacitors. If I put a 1MOhm ...
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Best method for generating low current (5 - 10 mA) -2.5 V supply

I am designing a digital system with various power supplies. I need to generate positive and negative supplies for a component. The voltages are +6.5 V and -2.5 V. Both supplies will pull in the ~5 ...
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How to calculate accuracy of LDO

I will be using a TPS7H1101A LDO and wanted to calculate the accuracy of it. I see in the datasheet they list the output voltage accuracy of +/- 2%. I think this number in some datasheets covers the ...
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How to make AT90USB646 run at 3.3v VCC?

[WHAT I DID] I've made one prototype of AT90USB646 running at 16MHz, 5V. The design is almost the same as Teensy++ (schematics can be found here https://www.pjrc.com/teensy/schematic.html). [WHAT I AM ...
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How to configure LDO output

I am using an LDO to convert a 5V rail to 3.3V for a microcontroller. I am using the TLV707 from Texas Instruments. It gives a recommended schematic as shown here: and I have used this. I have used ...
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ESP32 3.3V Voltage Regulator

I'm designing a circuit which will include an ESP32 and 5V DC power provided by a AC/DC SMPS. The 5V is needed for other components in the circuit and I would like to power the ESP32 through its 3v3 ...
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LDO power dissipation

I am trying to design a split power supply from lithium-ion batteries to use with different portable audio projects. In order to have a stable power source, since it comes from batteries, it has to be ...
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LDO with PWM as VCC

I have a 5V fan that needs to be controlled by a 12V PWM output (the PWM is there to control the fan's RPM). Can I use an LDO to step down the 12V PWM to 5V? I'd connect the 12V PWM as the voltage ...
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Vin-Vout Difference vs Dropout Voltage (on the LDL1117 regulator)

I have identified the LDL1117 (specifically the LDL1117S33R) to reduce a 4V DC voltage to 3.3V DC. The max current draw is 500mA. I had initially selected this part because I read the dropout voltage ...
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Low power design - Adjust Vout of a adjustable LDO with feedback voltage from Lipo

TL;DR: Using LDO to drop voltage from Lipo to stable 3V LDO Vout can be adjusted with Voltage Divider Lipo from 4.2V to 3.4V, Vout = 3V Lipo below 3.4V, Vout = 2.3V => How to adjust Vout of LDO ...
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Is there any drawback to directly combining two DC outputs of same (similar) voltage?

I'm designing a module that acquires power from two different sources: USB (5V) or I2C (3.3V.) The USB power routine is converted to two different 3.3V outputs (say, 3.3V1 and 3.3V2) by two different ...
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Problem stabilizing this PMOS LDO

I am considering a discrete LDO for a supply rail that needs ~\$m\Omega\$ impedance at 10 kHz. While the following circuit does what I need (according to Spice), it becomes unstable if C2 is smaller ...
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ESP8266/ESP-12F gets damaged when powered by LDO (LD1117v33) every time

Every time I connect a new ESP8266 (ESP-12F) to a new LD1117v33, as long as I insert an ammeter in between, it runs fine. It consumes about 70mA during normal running, and almost 0mA when in deep ...
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DC split supply from Li ion battery

My goal is to design a split power supply that I can use for different audio project. I need a +-2.8 V supply. My power input will be a 3.7 V nominal Li ion battery (or two of them). My questions are: ...
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5-24 Voltage Input to 5V/500mA Output

I'm looking for an IC with fixed 5V output voltage and a maximum of 500mA (USB standard). I've searched and found some buck converters and LDOs the problem is because of their drop voltage, when Vin=...
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Is it true that buck converter FETs are driven from LDO?

As per the below document https://www.onsemi.com/pub/Collateral/TND388-D.PDF higher switching frequency has the drawbacks listed. Iam unable to understand Is FET driver in a buck converter internally ...
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Line regulator's oscillation , phase margin?

Hi I'm studying LDO with LTspice, with tsmc180nm library. During simulation, I cannot understand this situation... I can obtain this OPEN LOOP GAIN simulation, with phase margin of 50 degrees, at ...
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DC/DC output ripple voltage

Our team is using TI's TPS62740 IC as a DC-DC converter in our device. At Vout (without connecting load) I get a sawtooth waveform of about 9 mV peak to peak. After adding a 2nd order low pass filter ...
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Why does this PMOS LDO require no compensation to be stable?

LDOs with PMOS pass transistors are prone to oscillation due to positive feedback problems as discussed e.g. here. Now the below simple circuit is basically a PMOS LDO, but seems stable in both time ...
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