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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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166 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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1answer
46 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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2answers
82 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
73 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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102 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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1answer
57 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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1answer
31 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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2answers
31 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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50 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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2answers
79 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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3answers
132 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
73 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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1answer
115 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 ...
16
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1answer
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
47 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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2answers
122 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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1answer
87 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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61 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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49 views

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
88 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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1answer
140 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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4answers
296 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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3answers
115 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) ...
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3answers
122 views

How to improve an elegant design for an LED dimmer, low-powered with LDO

I am building a sunrise alarm clock. The LED is supposed to get brighter over the course of 30 minutes, then remain fully lit for another 30 minutes, then switch off. I am using a digital pin on an ...
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1answer
240 views

Why do I measure 5V in this circuit when I should measure 3.3V?

I have an audio processor board that has a 5V -> 3.3V LDO. For some very strange reason, when I measure the voltage of the output of the LDO, I read 5 instead of 3.3V -- which by the way is a lethal ...
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2answers
61 views

Can I use an LDO to control several diodes at a speed in the order of kHz?

I wish to control the switching on and off of several LEDs as indicated in the following figure: simulate this circuit – Schematic created using CircuitLab The bases of transistors and the ON/...
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1answer
53 views

Variable LDO implementation - capacitor size

I am designing two linear power supplies that will: Drop 9V DC to 5V DC to power a Raspberry Pi around 2.5A Drop 9V DC to 7.5V DC to power a DAC under 3A I plan to use Texas Instruments LDO UCC283-...
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1answer
93 views

LDO in split supply behaving incorrectly when power supply sequence is “wrong”

I'm powering an op-amp (OPA657) in transimpedance configuration. I externally supply ±15V, with LDOs to drop to ±5V; here I omit the feedback loop for simplicity: When I turn on the negative rail (-...
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1answer
109 views

How can I enable a LDO using the I2C SCL signal

Can I enable/disable an LDO (more specifically NCV8163AMX280TBG) by using the I2C SCL signal? This would allow me to turn ON the regulator once a master starts the I2C protocol and turn it off once ...
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1answer
34 views

LM2940, 7808 and Multichannel PWM chip

I'm putting together a circuit board to power and dim 5 LED channels. The average voltages on the channels are 12.3V, 11V, 11.4V, 7.8V, 6.6V, and max current is 1A. So my current plan is: 12V ...
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2answers
61 views

LDO ground with Diode for temperature Drfit compensation

I work the below circuit. LDO is 3.2V fixed , Two diode is connected one at output and one at ground for compensate the temperature drift occur. Op is connected to a micro controller VDD-BUS which ...
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132 views

Laser Diode Driver and Cooling

I am a newbie at analog design, and trying to design a laser diode driving circuit and TEC cooling circuit for a 14 pin laser diode, such as P1550-ADF-B: 1550NM ADF LASER DIODE which has forward ...
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2answers
460 views

What is a simple voltage limiting circuit?

I am searching for a neat solution for an input voltage limiting circuit. Situation: I have a circuit with an input voltage range from 6 V to 20 V at 3 A peak (the load), however my source can be ...
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4answers
453 views

How do I measure very low frequency noise?

I'd like to measure low-level noise in the 1 Hz to 100 kHz range, for example at the output of a LDO. For higher frequencies a spectrum analyzer would do the job, but most only go down to the MHz ...
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2answers
2k views

Ferrite instead of LDO

Currently we are using the following power supply scheme: This solution effectively separates the analog sub-part of the PCB from the noise of the digital sub-part. Now we are going to use the ...
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1answer
99 views

High pitch sound coming from Low-Dropout Linear Regulator (1117 3.3V) setup

I am using the below schematic to drop voltage from 5V to 3.3V (1117 3.3V - http://www.farnell.com/datasheets/2100276.pdf?_ga=2.141255921.210515873.1532314816-790306462.1508240417) for a Wifi Micro-...
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2answers
247 views

In a simple LDO regulator, is the op amp working in positive feedback?

Below they're connecting the feedback voltage FB to positive pin of op amp. Isn't this positive feedback ? Because, when the output voltage increases, the feedback voltage increases, which then ...
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3answers
282 views

XBee power supply design using a Li-Po 3.7V battery

I'm currently designing the power supply for a device which uses XBee PRO S2C as a medium of communication. We are using a Lipo battery 3.7V 3500 mAh battery and TP4056 based battery charger. The ...
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2answers
227 views

Converting 8-24 V AC into 3.3v DC

I have a circuit running an ESP-12 at 3.3v DC that I would like to power with a doorbell transformer that will deliver between 8 and 24v AC. I was wondering what would be the best way to do that. I'm ...
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0answers
159 views

LT3045 LDO regulator start-up problem

I was using a voltage regulator based on LT3045, everything worked fine but after powering the device after longer time of not using it, it stopped working. The output voltage that i'm getting after ...
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1answer
345 views

MOSFET LDO, how does it work

I can't understand how MOSFET LDO works and when it would be low drop. Below, there is a simple schematic with N channel mosfet and TL431. Providing gate voltage, D-S will open, but minimum Gate-...
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1answer
68 views

Worst case circuit analysis question

How to start with worst case circuit analysis (performance analysis) of a power supply circuit which includes LDO , resistors , capacitors , inductors. Part data base development is done. I need to ...
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3answers
157 views

What is the worst-case PSRR of an LDO?

For a low dropout regulator, what does the worst-case PSRR (power supply rejection ratio) mean? I know what PSRR is, but I am not sure in what case the PSRR of LDO is the worst. Thank you!
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2answers
84 views

What kinds of inputs can an LDO take?

I just recently stumbled across LDOs and understand that they are used to regulate an output voltage. I understand that they require a differential amplifier, a reference voltage, and a pass element ...
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0answers
81 views

1117 voltage regularo ceramic caps

I have made a mistake and I do not have the space on my PCB to add two serial resistors. Is it OK to use only one for two caps? Simulation looks OK but it only the simulation
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2answers
183 views

Linear regulator that regulates even with negative current?

I require a voltage source which holds a large capacitor at a stable voltage. The following secenarios must be supported: Something is feeding current into the capacitor. The voltage source needs to ...
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1answer
60 views

LCD AMS1117 ceramic capacitors

I need to use 0603 ceramic capacitors as I do not have enough space on my PCB. Do I need to add small resistance in series (1-2Ohm) as they have a very small ESR comparing to the electrolitic ones? Or ...
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4answers
1k views

Capacitors with an LDO voltage regulator - how necessary is it?

I’m planning on using an MCP1700 to drop the voltage of a lithium polymer battery from 3.7 V to 3 V. The battery will be connected to the regulator via a charging circuit (https://www....
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1answer
64 views

LDO Voltage Regulator - What happens inside dropout range?

I’m using this 3.3V LDO (https://www.sparkfun.com/products/526) to power a device which normally takes 2 AAs (3V), using a 3.7V LiPo battery. The device won’t power on without the regulator (it can ...
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0answers
290 views

low dropout voltage regulator mosfet region of operation

I am trying to understand LDOs.I read that the crux of voltage regulation using LDO is modification of resistance of series pass element.In case of MOSFET as a series pass element,it should operate in ...