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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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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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113 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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50 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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57 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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35 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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36 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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68 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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246 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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75 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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96 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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221 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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58 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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49 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
48 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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86 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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26 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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53 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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84 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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147 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
228 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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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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88 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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171 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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142 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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133 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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96 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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226 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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57 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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115 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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75 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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60 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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155 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
46 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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50 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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222 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 ...
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111 views

LM1117 same output as input

I have an L298 Dual H-Bridge DC Motor Controller which comes with an LM1117-5 voltage regulator. I want to use this regulator for a logic level converter to go from 3.3v to 5v. I have one board that ...
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131 views

Help identifying a sot-223 ldo voltage regulator

I can't seem to identify this. It's a 1117c but I need to find the correct output voltage. I don't recognize the manufacturer logo. Thanks in advance.
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Best way to power an ESP8266 (3,3V) from AA batteries with LDO

My latest project uses an ESP8266 (ESP-01) to transfer data when a button is pressed. The ESP is always connected to the AP. No deep sleep. Right now I am powering it with an USB-charger which is ...
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168 views

IC voltages and low power design, What todo?

I’m working on a low energy device consisting of a couple of IC’s. What is confusing to me is the following, All ICs has a vcc supply range of 1.7 to 3.6V and most of the time the current reading is ...
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115 views

Please critique my high-current voltage regulator [closed]

A project I'm working on requires a source of power which need to be both regulated (5.00V) and high current (~4A). An external power source may be any from 6V to 12V but it can be assumed that it can ...
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42 views

LDO Load test-Oscilloscope Setting

I am performing a Load test on an LDO. I will be measuring: Input current Input voltage Output current Output voltage. In the oscilloscope measurement settings I can see MAX, MIN, MEAN, RMS, PK-PK ...
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4answers
296 views

What could cause an LDO regulator to fail to regulate properly? [closed]

First, some background. I have two boards, Board A and Board B. Two separate, but extremely similar designs. Let's start with the similarities: Based on AVRXMega Exact same regulator setup. 5V in, ...
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1answer
43 views

Buck converter or LDO with multiple voltage levels

I'm designing a project at the moment that will be powered by USB-C. There's more information about that in this previous question of mine. The project can be easily split into two parts: Control/...
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2answers
185 views

LDO with tantalums and circuit with ceramic bypass capacitors

I'm going to use MIC5205 voltage regulator. According to the datasheet and many sites and discussions I must use tantalum capacitors for the output. This LDO is unstable with ceramic capacitors (low-...
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110 views

LDO Regulator Power Good Output Pin Question

MCP1755 has Power Good Output (PWRGD) output pin which is open drain. In page 15 of data-sheet it says The PWRGD pin may be pulled up to VIN or VOUT. Pulling up to VOUT conserves power when the ...
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276 views

TL431 LDO series pass transister heating up

I designed a low drop out 5v voltage regulator from 24v input. Works fine. But the series pass transistor heating up more than 100 degree Celsius (with heat sink). Is it normal? Or how to reduce heat? ...
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633 views

LDO Output Capacitor Selection and ESR Consideration

For a simple application of a voltage regulator with 5V in and 3.3V out, I am looking at these three regulators. 1)AP2127K-3.3TRG1 2)MIC5504-3.3YM5-TR 3)TLV73333PDBVR They all have different ...
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2answers
259 views

How does the current draw of an IC change with supply voltage?

Suppose I have a device with a number of ICs (microcontroller, logic gates, MEMs sensors, etc) which can operate from a supply voltage in the range of, say, 1.7V to 3.6V. Will the current draw be ...
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2answers
350 views

LDO voltage regulator with passthrough

I'm trying to design a circuit that will power my 12V LEDs. The battery should be 12V and up to 14V when charging. I would like to route it through an LDO voltage regulator when the battery is ...