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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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37 views

Low Dropout Regulator Enable Delay

I have a main buck DCDC 5V that feeds to five different LDOs(3.3V). To create power sequencing, I would like to use a resistor and a capacitor at the input of the enable pin of each LDOs and by ...
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24 views

Making a redundant power source

I want to have redundant power sources for my load in case one of the sources fail. i have 2 separate dc power sources ( from chargers ) and both is rated 5v 2.a. According to my understanding and ...
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Reverse Current building up Voltage

Just wanted to clarify my understanding before I design my circuit. This is based on my previous question I have an 3.3V LDO Regulator. Vin = Regulated 5V Vout = 3.3V Load Current = 100mA. At ...
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55 views

Effect of Pi Filter on the Output of LDO

Similar to my previous question on +5V Sneak path, I ran into another question now. I have this circuit as shown. I have an Pi Filter at the Output. ATT has 600Ohm Impedance at 100MHz and 0.1Ohm ...
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33 views

Mitigate TPS56* ecomode ripple effect under lighter loads

Following my question Powering up analog part of the video card (thanks everyone for their inputs and advices) I have chosen the devices, and even have drawn the circuit diagram of 12 V to 5 V power ...
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78 views

Microcontroller and LDO and +5V pull up sneak path

I am using this 3.3V LDO whose input Vin=5V (regulated input.) Output is 3.3V with load current of 200mA This 3.3V is given to this Microcontroller for GPIOs. I have taken 2 outputs (these are ...
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53 views

Adjustable LDO feedback resistor values

I'm designing a circuit using an LDO voltage regulator; specifically the LD39130SPUR from ST. This variant of the part allows for an adjustable output voltage via a potential divider as seen on page 8 ...
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1answer
123 views

LDO Heating Issue

I am working on a PCB project and having a problem with the linear regulator IC. I want to be able to maintain a relatively constant temperature for the heating element. The whole system is ...
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91 views

Low Quiescent LDO vs. Buck Converter: Which is better for low power applications?

I'm stuck between choosing to use either a buck converter or a LDO voltage regulator for my heated glove project. The voltage regulator's function in question will be to power the microcontroller. ...
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57 views

Multiple rails I2C bus device from PMIC

I want to use a PMIC chip in my project. As any PMIC, it has a couple of outputs: buck Vout, and an LDO out. The PMIC is operated over the I2C bus. The MCU acts as the host device and runs on Vout, so ...
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62 views

Is it possible to use an LDO as an Auxiliary source to a smps?

My SMPS controller can supply about 250mA and 3.3V output. There are rare but crucial moments when power demand goes above 250mA, voltage sags below 2.7V, and the MCU brown-out occurs. The ...
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81 views

What are the differences between LDOs for positive and negative voltages?

I am trying to understand the negative LDO. I have the following questions regarding that: What is the main difference between positive and negative LDO? Is the reference voltage of LDO connected to ...
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86 views

LDO voltage regulator, no output

I'm making my own board based on Arduino. To power it I use one LIR2032 cell (button cell 3.6V li-ion battery) that's driven through 3.3V LDO voltage regulator. So far I have tried two different ...
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49 views

Stable LDO voltage when Vin goes down momentarily

I have an application where Vin comes from a battery pack (3V - 7V) but on occasion and under heavy load, Vin drops to just above 2V for ~ 1 seconds before recovering. There is a 3.3V LDO that ...
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74 views

Is it possible using two 3.3v LDOs from one SMPS AC-DC 5V to power 2 MCUs?

I'm planning to use two 3.3V LDOs to supply power for two MCUs, one is STM32, one is ESP-12. Input power of these two LDOs come from one SMPS module 5V, 3W (HLK-PM01). The reason for two seperate LDOs:...
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Problem using 5V LDO (AP7381) as power source for Arduino

Goal I'm trying to build a portable speaker. I want to use an arduino to handle several tasks. The speaker uses a 6s Lipo ~24v as power source. An LDO the AP7381 has been selected as power source for ...
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48 views

MCP3008 sharing power supply with low-noise DAC

Asked this question on the Raspberry Pi Stack exchange and was redirected here! I'm designing a low-noise audio gadget that uses an MCP3008 ADC (for sensors) together with a Raspberry Pi and a ...
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79 views

LDO vs Switching Voltage Regulator for Drone Application

I have been designing a drone flight controller and currently have been using LDOs to regulate the voltage to 5V. As I have started to use higher voltage batteries the LDOs have started to overheat. ...
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91 views

Negative current displayed on the power supply

I have a problem regarding the power supply and my circuit. As the picture shown, my power supply is connected to a voltage regulator, Low Dropout Voltage regulator (LDO) to be precise. The part ...
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1answer
88 views

Drawback of using Schottky Diode to lower MOSFET threshold voltage?

I am considering using Schottky diode to lower PMOS's Vth as the following diagram: As the current extracted from Schottky diode is small enough to provide 0.3-0.4V voltage drop, PMOS's threshold ...
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1answer
144 views

Test cases for for OTA in LTSpice

Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice. I reffered this link for ...
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123 views

Output capacitor in LDO regulator

I want to use an Analog Devices LDO regulator (ADP7104ARDZ-5v.) When I checked the datasheet, I found out that it requires just a 1uF capacitor on the output pin. Then I searched more and I found an ...
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Analyzing and Improving Power Filtering

I have a wireless radio NRF24L01+ hooked up to a 3.3V LDO voltage regulator. The battery that powers the LDO also powers high current motors. The NRF24L01+ already has 100uF capacitors near the device ...
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128 views

Latching power with LDO enable pin

There are lots of examples of latching circuits that use a single momentary push-button to turn on/off a circuit by combining two or more transistors. Some examples are: Simple soft power latching ...
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125 views

How can calculate the turn-off time of an LDO?

This is the datasheet of TPS7A8101 LDO I am analyzing. In the datasheet, start-up time of the LDO is given as 80 ms for given conditions. My question is, how can I calculate the turn-off time of the ...
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79 views

LDO as a constant current LED driver

I am doing some research about using a LDO as a constant current LED driver and For this project, it is imperative that the LEDs remain as stable as possible. I also need to be able to easily adjust ...
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1answer
73 views

Split capacitor PCB mounting?

I've been looking at the PCB layout for the LT3045, a high PSRR LDO. The datasheet of the LT3045's demo board, the DC2491A, includes a recommended PCB layout. One section of the datasheet mentions ...
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187 views

Difference Between RMS noise and PSRR in an LDO

I am trying to choose a low dropout linear regulator to partially smooth the output of a dual rail SMPS I'm using to power analog circuits. I'm confused about the difference between the specified RMS ...
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72 views

Low pass filter vs low noise regulator

I’ve been spending a lot of time looking at different low noise voltage regulators, and it dawned on me-why am I not just putting a filter on the output of the regulator I already have? What are the ...
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102 views

High frequency reduces power on circuit

I am not expert in electronics so there must be many errors that I am not considering. I designed a simple half wave rectifier that gives signal to a LDO voltage regulator of 3V3. In the input I have ...
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1answer
79 views

Powering phone using LDO regulator on battery terminals - what reservoir cap to use?

I have rigged up an old phone that does not run without a battery by attaching an AMS1117 regulator to the battery terminals. The regular is fed from +5V USB, and outputs 3.3V. The regulator comes on ...
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133 views

3.3V LDO Selection

If you've ever tried to find an appropriate LDO for your project you may have noticed the incredibly vast range available on the market. During my searches, I discovered this particular regulator ...
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70 views

Why does adding a capacitor to the adjust pin of a voltage regulator improve PSRR?

When looking into the datasheet of an voltage regulator, they often recommend adding a capacitor from the ADJ pin to ground, to improve ripple rejection. It can also often lead to an significant ...
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33 views

TLE42744 outputs lower voltage than expected

I am an engineering student and have just finished designing a PCB containing an STM32F405 MCU, an LSM9DS1 Accelerometer/Gyroscope/Magnetometer and 7 connections for potentiometer reading. My power ...
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34 views

LM2937 Replacement/Upgrade Thermal issues

We are using an LM2937-5v LDO regulator in an SOT223 package - currently flowing approx 150mA with a 14V input (9V drop over it), and, as you can imagine it gets quite warm: 70degC (though from my ...
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91 views

Ultra Low Power, LDO Enable from RTC vs. deep sleep MCU interupt

I have a question regarding optimising design for ultra low power consumption device. I'm trying to develop a remote sensor node that should measure and send data every few hours. Currently I have an ...
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106 views

Read voltage of the battery that feeds ATmega328p

I am designing a system focused on the uC ATmega328p and I am feeding it directly with a 3.7V LiPo battery. I also have a 3.3V LDO feeding several sensors in the system. My question is the next, If I ...
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231 views

Use 5v Linear Regulator and LDO 3.3V

I am designing a PCB with a STM32 microcontroller, a GPS, DataLogger and X-Bee module. The power supply is a 12V Battery. So in my project I need 5V and 3.3V, at the same time. I don't know if it is ...
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1answer
119 views

Questions about a design for an SMPS post regulator filter circuit?

For minimizing SMPS ripple and especially noise, I’m trying to make a small interface which is a post regulator cascaded after an LC filter. I have come across some papers related to this topic and ...
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123 views

How does the coupled inductor, capacitor and diode combination work?

I was reviewing a buck regulator circuit. Circuit was designed for 3.3 V output (Vout1) simulate this circuit – Schematic created using CircuitLab From this buck regulator output, a coupled ...
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4k views

What is the purpose of a 1 Ω resistor to ground in the output filter of a voltage regulator?

This is the LDO regulator I am analyzing. While I was a referring to an existing design based on LP2951, it is noted there is an additional 1 Ω resistor at the output filter capacitor to ground. ...
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1answer
74 views

Voltage Regulator for GPS vs. BMP280

I am using the Bosch BMP280 pressure sensor and the FGPMMOPA6H GPS chip together on a PCB. I am using the reference designs from Adafruit's breakout boards for each chip (found via the product links: ...
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141 views

Keeping voltage above 3.7 Volt with a lipo

I am driving an audio amplifier with a 3.7V lipo. With a latching circuit in front. [![enter image description here][1]][1] The problem is, that when I turn up the volume, the voltage drops under ...
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118 views

Feeding AMS1117-5V with 3.3V [closed]

I need that an Arduino NANO clone work with 3.3V. Can an AMS1117-5V give 3.3V if supplied with only 3.3V? edit: current consumption is 400mA max. the AMS1117 output current is 800mA.
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65 views

Can I use same LDO for two outputs?

Can I use same LDO for two or three outputs? Given that the LDO provides enough needed current for three devices.
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Reverse voltage on MIC5225 in particular and other LDO in general

This question has been asked many times before, for example about LD1117, MCP1703, LM78M05CT, MIC2920A, ADP7142 etc. Why am I asking it again? a) From reading all those topics it seems that the ...
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1answer
215 views

How to connect two LDOs in parallel?

I have two LDOs that convert different input voltages into the same voltage. I'm not sure how to safely connect the outputs together so they become the same signal and can be both be used to power the ...
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197 views

LDO, linear regulator or DCDC buck converter

I would like to power an ESP32 in my car, so the input voltage is between 11 and 15v, and the output voltage should be 3.3v to power the Arduino board. I thought that LDO were only for low dropout ...
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325 views

How to convert a wide voltage range (1 V-12 V) to 5 V?

I have an unusual application where the input voltage can vary from 1-12 V DC. This must be converted to 5 V @ ~200-250 mA. Since there are no available buck-boost converters suitable for this wide ...
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149 views

Understanding power dissipation by LDO regulator as it relates to battery life

We are looking at using an AP2204K-3.3TRG1 to convert 6V from 4 AA batteries to 3.3V to power a microcontroller. I found that the efficiency of a linear regulator is (ignoring quiescent current) ...