Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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 vs. voltage reference

I need a cheap, somewhat accurate (~0.5%) voltage reference for some DACs. At first I was going to use a LDO voltage regulator (a TC1223 specifically) for this, it seems to fit the bill looking at the datasheet. Then I saw there is a separate…
GrixM
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Arduino Uno R3: Directly supply regulated 5V to 5V pin?

I'd like to use an Arduino Uno R3 battery powered a datalogger. I want do supply it directly with a Step-Up regulated 5V rechargable battery powersource at power pin 5V. I don't want to suppy it with 5V at the PowerJack or Vin because it's not…
try-catch-finally
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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 gave a concrete example in the lab: at 10 kHz input…
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Why are low-dropout (LDO) voltage regulators unstable?

LDO regulators based on P-type transistors seem to be the preferred form of linear voltage regulator today, but I keep hearing about how I have to choose the output capacitor(s) carefully to guarantee stability. The older high-dropout regulators…
Adam Haun
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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. What is the purpose of adding a 1 Ω resistor? How is…
vt673
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For a small Vin-Vout difference, is it worth using an LDO vs a buck regulator?

I want to step down 5V to 3.3V at around 250mA. As far as I see it, there are two options to consider: Buck: more space, higher cost LDO: less space, lower cost, more difficult to remove heat(?), less efficient(?) What I am wondering is will the…
Thomas O
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What is the difference between a linear regulator and an LDO

Can someone tell me what the difference between linear regulators and LDOs is? From what I have read and understood, it is that linear regulators and LDOs don't use switching elements, but I think they are the same basically. Is there something that…
user220456
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Tantalum capacitors vs. ceramic capacitors

I have a negative LDO (-5V from -5.5V to -10V) which requires a tantalum or aluminum capacitor. I'm wondering why it can't use a ceramic capacitor? Is there any specific reason for this? Regulator is a TC59 (datasheet). (Correction: the regulator I…
Thomas O
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Layout advice for LDOs

I'm developing a four layer board which is powered by 3 voltages - 1.8V, 3.3V and 5.0V. The board has the following stackup: Signals Ground 3.3V Signals The ground and 3.3V plane are completely unbroken. No signal or power trace travels on…
Saad
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Does PSRR improve with multiple LDOs in series?

Would having multiple LDOs with different output voltages are in series, for example: 5 V from a buck converter -> LDO1 (3.3 V) -> LDO2 (2.8 V), and assuming all LDOs satisfy the dropout voltage requirement, provide better power supply rejection…
Yuanyi Wu
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How to reach ~50nA p-p current noise in ~200mA current source?

Target application is driving single-frequency laser diodes (@2.5V) which are sensitive to current noise. Current is constant, with no modulation. Strightforward solutions that first comes to mind is low-noise LDO (for example LT1963) that can reach…
BarsMonster
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Best solution to get 3.3V from 5V-20V @ 250mA

For my Super OSD project, I need a +3.3V supply at 250mA from a variable input of 5.5V to 20V. Cost is a concern, as is size. Originally, I considered an LM317 in a SOT-223 package, due to the small size. Unfortunately, it's difficult to get a…
Thomas O
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Why do LDO regulators have so big a voltage drop?

Why do LDO linear regulators not use MOSFETs as the main component to be able to have minimal dropout=0 (well, depending on current, must be still a few mV)? Or can one expect to build a 0-dropout regulator based on a MOSFET and an opamp?
BarsMonster
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Adjustable LDO Regulator

I'm using Microchip TC1071 in a circuit to provide an adjustable output voltage (appears to be pin compatible with LT1761-SD). My plan is to use a digital potentiometer (Microchip MCP4251) to control the output voltage within over some range. The…
vicatcu
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Replace AMS1117 5V-3.3V LDO on NodeMCU for LiPo with low quiescent current

I want use my NodeMCU to drive a SIM808 Module with integrated LiPo Charger. https://www.itead.cc/wiki/SIM808_GSM/GPRS/GPS_Module There are two problems. First of all the SIM808 Module just provides the LiPo Voltage, no steady 3.3V or 5V output. The…
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