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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72 views

Voltage Regulator Overheating

I'm currently designing a simple PCB that uses a MAX3221 to send/receive RS232 over an ethernet cable along with an optional 1-wire thermocouple reading (The thermocouple breakout can be soldered in ...
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5-pin SMD device identification - top marking CaC9A

Please help me to find the name of this SMD device with top marking CaC9A
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100 views

Can I use a low dropout voltage regulator to drop a 5V 100 nSec pulse to 3.3V?

I am using an analog switch IC with 3.6V as a maximum operating voltage. The input to the analog switch is the output pulse from a multi-vibrator which is 5V and 100nSec width. I need to drop the ...
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40 views

Recommended high-PSRR LDO regulator? [closed]

I'm having a hard time finding a regulator that fits these constraints: High PSRR (>80 dB @ 0..50 kHz), low noise. Vin = 5.5V, Vout = 5V, IoutMax = 200mA. Dropout voltage preferably < 200 mV. ...
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Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

Background In EEVBlog #1116, Dave discusses a method to remove power supply ripple, and goes on to show (see 5:17 to 6:15) that you cannot count on linear regulators to remove your input ripple. He ...
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LDO with 2 input sources [duplicate]

The following LDO is supplied from 2 input sources. BAT, which is a battery from 2.5-4.2V and VBUS, which is a power adapter voltage of 12V. My understanding is that a diode has a forward voltage drop ...
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1answer
46 views

Device current consumption [closed]

When I power off and on my device, it draws around 90mA and after sometime (around 1-2 min), the current value drops to around 40mA-50mA. Is it because some of the ICs go into standby mode after a ...
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1answer
50 views

DAC controlled LDO as current source - Pt.2

This is a follow-up question which references to "DAC controlled LDO as current source.". I am now trying to use the recommended LTC6363-0.5 as seen in the schematics. This is a fully differential OP ...
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1answer
99 views

5A constant current/ constant voltage using LM350

I take the circuit below given in a TI application note, and I have some questions about the way the circuit works: The circuit is designed as a 5A constant current/constant voltage regulator. First ...
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2answers
111 views

DAC controlled LDO as current source

Currently I use a LT3083 as a constant current source more or less according to the datasheet as given in the first image. Instead of a single set resistor however is use a fixed resistor in series ...
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4answers
134 views

LDO output voltage lower than expected

I'm aware the same question has been posted before, but unfortunately, it has not led me to an answer. I have a small PCB in which I've added an LDO to convert input voltage to 3.3 V output voltage. ...
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1answer
83 views

LDO requirement for battery powered micro-controllers [closed]

What are the selection parameter for battery powered ultra low powered application? (Battery capacity of 3700mAh, 3.7V 18650 Li-ion) I'm designing an application with MSP430/Atmega328 + RF micro-...
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1answer
28 views

Signal to Noise Ratio and Inflection point (PSRR measurement in Oscilloscopes)

I have a 3.3V LDO for which I am supposed to do the PSRR measurement. I have a keysight scope to do this. While looking at this PSRR YouTube tutorial from Keysight, I have a few doubts. Around 5:...
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660 views

At what point should I switch between a resistor divider and a LDO?

My problem is that I have a RF chip which is supplied 3V3 and interfaces with my MCU over 1V8/2V8. I have an external source of 3V3 which will supply the RF chip. I'm space restrained on my PCB and ...
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1answer
69 views

How can I protect LDO NCP1117 from overheating due to short at output?

I use NCP1117 to supply voltage to various chips, such as the STM32 and buffer driver, voltage sensor, digital insulator ect. But if any of these chips fail, the LDO will heat up. What should I do? ...
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70 views

LDO pass transistor operation region

I am studying about LDO and I came across this App Note While reading, I encountered the following questions. At the end of first paragraph, they mention "This is a closed-loop system based around ...
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78 views

Formula for RC delay time

I found this formula used in a circuit to calculate the RC delay time. Can someone please explain what it means? *Delay time = - 14.7K * 4.7uF * ln(1 - (1.2/5))= 18.96ms Thank you
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Linear regulator doesn't keep the right voltage when connected to ESP8266

I am trying to use a MCP1700-3302E LDO to regulate voltage from single-cell LiPo battery to my ESP8266 (Wemos D1 package). I intend to use the LiPo down to 3.5V, and since ESP8266 requires 3.3V, that ...
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41 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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32 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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1answer
64 views

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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75 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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1answer
40 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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89 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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68 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
149 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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1answer
235 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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61 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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69 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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1answer
96 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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1answer
105 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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97 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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81 views

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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58 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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88 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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111 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
103 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
293 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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166 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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298 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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144 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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2answers
149 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
110 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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1answer
193 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
127 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
112 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
83 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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139 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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