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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26 views

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

I'm planning use two LDO 3.3V to supply power for two MCU, one is STM32, one is ESP-12. Input power of these two LDO come from one SMPS module 5v 3W (HLK-PM01). The reason is I'm using STM32's ADC and ...
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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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65 views

DC-DC conveter, LDO [on hold]

Can I use a low-drop out (LDO) regulator instead of a DC-DC converter to go from 24V to 3.3V? I heard efficiency also matters, can some one tell me complete information?
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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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Single LDO for powering LMX2582(RF synthesizer) and HMC987(Clock Buffer)

I am using LMX2582 and HMC987 for providing sampling clocks to three RF sampling TI ADC12DJ3200. LMX2582 will generate 3.2GHz and give it to HMC987. Then three outputs of HMC987 will be connected to ...
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72 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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74 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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81 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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70 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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113 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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54 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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115 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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58 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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59 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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179 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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57 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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86 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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77 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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122 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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63 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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32 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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32 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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59 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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88 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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163 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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92 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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119 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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55 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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130 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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104 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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63 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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57 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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144 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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157 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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308 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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129 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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132 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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252 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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65 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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56 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
95 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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115 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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38 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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63 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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145 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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584 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
539 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 ...