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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3.3V regulator does nothing for first ~12 seconds after power-on, then outputs 5 volts
In my circuit I'm using a TPS78633DCQ low-dropout regulator to regulate my 5 volts power input down to 3.3 volts. However, when powering up the circuit board for the first time today and measuring the ...
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2answers
58 views
Is it possible for a DC LDO to be able to take in AC and DC
I have an LDO TPS7B69 which takes in upto 40V dc and regulates it to 5v. This LDO typically take in DC, but i would also like it to be powered by AC 40volts peak max at 50Hz or greater.
Rectification ...
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3answers
73 views
MCU controlled power-on sequence
I would like to implement the power-on sequence of an IC. It has 3 different power supplies plus the clock, which has to be enabled after the power supplies. I am considering employing a ATTINY202 for ...
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2answers
66 views
LDOs in series and impedance
I am unable to understand one thing. I have a 2 LDOs in series , the first a regular LDO with a normal impedance and second is a shunt regulator with an ultra low impedance .
What will my load see... ...
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23 views
LDO draining power
I have this weird issue with a TI LDO behaving badly.
In the picture note that I have 2 connectors which can be plugged and unplugged. Connection 1 is just a 5V power supply and connection 2 is a MCU ...
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1answer
30 views
Undervoltage Testing of a LDO or Switching DC-DC Converter
I am using a Regulator section in - UJA1076 this IC
Input Voltage = 16V
Output Voltage = 5V
Load Current = 0.1A
My question is, I want to test the undervoltage condition 90% and 70% as mentioned in ...
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4answers
189 views
LDO linear regulator output problem
I am using this LDO
Input Voltage is 14V
Output Voltage is 5V
Maximum Load Current is 150mA
Schematic :
I am observing two problems:
Problem 1:
Initially when I power on the LDO by given the input ...
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17 views
Solar Low Current Disconnect Options
I've built a system which allows me to remotely control a well pump which is directly connected to 24v solar array. There is a regulated battery bank/inverter, but it's farther away, and the pump is ...
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1answer
57 views
Is there something called as inrush current at the output of the DC-DC regulator or LDO
I am using this LDO to step down from 14V to 5V with a maximum output load current of 150mA.
The above is the schematic of my LDO.
I want to measure the inrush current of the LDO.
But since I have an ...
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3answers
32 views
3.3V LDO identification similar but smaller than SOT-223
I'd like to identify or find a replacement for a LDO component in the board above:
It's a 3.3V LDO.
It reads "AMS1117 3.3 DN18".
The body is around 4mm width.
Similar to SOT-223 package, ...
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2answers
52 views
Current limiting range on LM723 (from 0 to 5A)
I am building a power supply with LM723 and my intention is to have 0-30V and a range of 0-5A variable. I am regulating voltage normally, however for current limiting, if I want to regulate small ...
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48 views
Connecting multiple DC sources in parallel without the use of diodes
Obviously to have more current is there a way to somehow connect multiple DC sources together not by using trivial series Schottky diodes, but using mosfets and LDO(Low dropout) circuits? To somehow ...
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3answers
64 views
Reduce voltage before LDO
I am working on a remote gate opener setup. It will be powered via a 12v battery (12-13.5v) and charged via pwm solar charger at up to 14.5v. I would like to use the HT7333 LDO datasheet here
It has a ...
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1answer
94 views
How to properly model an linear power supply with LDO in LTspice?
I've build the following linear power supply:
Before building it I tried to model it in LTspice. I couldn't find an LTspice model of L4941BV LDO (datasheet [PDF]) or a suitable replacement. Thus I ...
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2answers
86 views
Adjustable DC/DC converter and/or LDOs for space application
I am currently designing a system for a satellite and I am looking into the components to generate the required low-voltages, and I was wondering if maybe the collective knowledge of stackexchange ...
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1answer
27 views
Using MCP1700-3302E LDO for Arduino/ ESP32 Solar projects
I'm using Solar-powered projects ( including batteries ), for remote sensing/ reporting.
When Battery drains below a certain voltage (~ 2.7-3.0v) due to lack of sun, MCU gets into "zombie" ...
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1answer
40 views
Altium error: “net contains multiple output pins” on LT3045 chip
I have two concerns:
Is it okay to have "contains multiple output pins error" in Altium?
Is anyone familiar with LT3045 chip? Its datasheet applications only have 1 "IN" pin and 1 ...
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1answer
54 views
Wall supply Plug-in “noise”
We have had some issues with resonance overshoot from our 10W wall supply to a products LDO. The theory is that this overshoot will destroy the LDO once in a while rendering the product useless.
While ...
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40 views
Phase margin plot of LDO
For this LDO circuit design at https://github.com/promach/LDO/tree/development ,
1) which exact circuit node(s) contributes to the zeroes near 1MHz after removing CL ?
2) If I remove "AC 1" from ...
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1answer
45 views
Linear dropout voltage transfer function
I am reading this application note from Texas instrument : http://www.ti.com/lit/an/slyt187/slyt187.pdf?ts=1591543592096&ref_url=https://www.google.fr/. The application note give us the transfer ...
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3answers
43 views
LDO output and input capacitor clarification
I would like to understand how to size the input and output capacitor of an LDO.
What I think to know:
About the input capacitor:
The input capacitor is used for filtering high frequency input ...
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1answer
47 views
Continuous Reset generated by LDO to Microcontroller
I have the below schematic
Datasheet of the LDO - L4995 -SSO24 package
LDO Specification :
Input Voltage : 12-16V
Output Voltage : 5V
Load Current : 100mA
Issue :
My LDO is generating RESET ...
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1answer
38 views
LDO datasheet dont provide open loop gain plot
To make LDO stable compensation. How to obtain open loop gain phase plot to compensate LDO, since it is not available in the datasheet.
Since its very much required for LDO load transient, load ...
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1answer
67 views
Strange Error amplifier of LDO
I am trying to work out what function the components in inverter colors serve, this is a schematic I have derived from a net-list to make it easier to explain my answer
...
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1answer
54 views
LDO datasheet parameter extraction
In similarity to previous question Ron setting of LDO. Unfortunately I assumed gain of the error amplifier and trial and error method I matched with dropout curve in the datasheet.
Query: How to ...
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2answers
41 views
What would be an LDOs output if the input is its rated ouput
I have an LDO TLV733 that output 3.3 volts. I need that the rail would always be 3.3v because anything below that the slaves data pins might get damaged because the host signal is 3.3v. The input ...
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0answers
17 views
What's the best option to power up a ComputeModule and a backlight LED with a battery?
this is my first foray in a complete PCB for the Raspberry Pi Compute Module (and my 4th PCB ever) and the first one with power management components. My background is Computer Science. I did study ...
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2answers
63 views
Delay in LDO Output
I am using this LDO
I want to know how to find the delay between my Input Voltage and Output Voltage.
Suppose my Input voltage to the IC is 12V and Output is 5V. How to find the delay between the ...
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1answer
46 views
Use one GPIO output to set two inputs to opposite states (low and high)
This is all still very new to me so apologies if this is a silly question.
I have two LDO voltage regulators, each of the ENable pins are different, to enable them one ENable pin must be LOW and the ...
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3answers
156 views
Discrete LDO Drawbacks
Clarification:
I appreciate everyone's input so far. The alternatives suggested are interesting, but for this application none of them seem better than the one presented here (except possibly ...
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1answer
27 views
Trade-off between LDO max Iout AND PSRR
PSRR is inversely proportional to output impedance of LDO.
But Iout_max of LDO is proportional to width of output mosfet (M20) , Rds of M20 is inversely proportional to width of M20.
Given that ...
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58 views
Why is this MAX86161 internal LDO wired this way?
I'm looking at the MAXM86161EVSYS and am not sure why the pulse-ox senseor LDO_EN and LDO output is wired this way
I see the purpose of R1A and R1B, to allow the ability to pull the enable high or ...
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70 views
How to choose the right ferrite bead for an LDO
I'm trying to design a custom board that will include the FGPMMOPA6H GPS.
Looking at the Adafruit integration of this GPS, I can see a ferrite bead on the output of the LDO (MIC5225-3.3). See below:
...
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1answer
57 views
Best way to switch USB power
I'm looking for a way to switch an USB device's power (a mini waterpump) digitally. I've found some solutions, however I'm not sure what are the advantages/disadvantages of the different approaches, ...
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56 views
Is 23.8°C/W junction-to-ambient thermal resistance for a TO-220 in this datasheet with or without a heatsink?
I've been reading datasheets all night trying to figure out which LDO linear regular would give me the most current at 3.3V with no heatsink from a 2S LiFePO4 battery (assuming a max voltage range of ...
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46 views
LDO circuit questions
I have done a LDO circuit at https://github.com/promach/LDO
I have few questions :
Why in the second bode plot (which might be problematic PSRR), gain going up near unity-gain frequency is often a ...
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5answers
117 views
What is the opposite of the Power Supply Rejection Ratio?
The PSRR of a device is the dB measurement of the power supply noise rejection. In my case, I have an LP5907 LDO with a PSRR of ~80dB, which would mean that if I have 10dBm of powerline noise on the ...
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0answers
28 views
Best connection node of sense pin for regulator?
I'm tring to get a high as PSSR as possible from my ADP7142 LDO. Observe the following application circuit taken from page 1 of the datasheet:
The softstart (SS) pin is not available on my package ...
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0answers
34 views
Calculating LDO thermal requirements
I've got a 5V supply, which I need to pass through an LDO to get 3.3V. The max current that the I need the LDO to support is 1A (at 3.3V). I'm looking at the TI LM3940. Using the DDPAK/TO-263 package, ...
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2answers
91 views
LDO quality with current measurement shunt
I'm designing a power supply block and need to measure the current flowing trough a LDO. It is clear that the current in front of the LDO and after the LDO are the same (apart from some tiny bit used ...
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27 views
LDO TPS7A54 Average Modelling
I am trying to do Average modelling for TPS7a54-q1, Looking at the parameters in the datasheet, I was able to find Line and Load Regulation data from which, I could approximate open loop Output ...
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1answer
25 views
LDO to Power ESP-12F
I am using HLK-PM-03 to power ESP-12F Chip with 3.3V, the recommendation by AI Thinker is to use 3.3V regulator with LDO. What is the recommendation from the community.
Should i remove the PM-03 from ...
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41 views
LDO and LDO Enable Pin typical usage
I have several power sources that are able to power the 3.3v rail in my circuit. Only the U2 needs to ever be disabled. The problem however is when PWR1In is brought up slowly and the other two ...
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1answer
77 views
Setting Rds(Ron) for PMOS for LDO
I am modeling LDO using ZXCL280 Datasheet. By understanding datasheet dropout voltage of the PMOS is seen as 1.46Ī©(From page 5 ...
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2answers
84 views
Ripple voltage for LDO
I would like to understand how to calculate the ripple voltage of an LDO.
Suppose I don't have an electrolytic capacitor.
I have a 3.3V output loaded with 50mA max with a ceramic output capacitor of ...
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1answer
35 views
LDO maximum output current during short circuit
I am using this IC - LIN Mini system basis chip - TJA1128
Using the LDO in that IC to generate 3.3V with 50mA of load current. I see that the maximum output current capability of the IC is 85mA.
...
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1answer
75 views
Battery backed up power supply using LDO
I was looking for a battery(12V, 11.2Ah lead acid) backed up power supply solution for my ESP microcontroller(3.3V) along with few relays(3V) and came across some reference design in the following LDO ...
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1answer
41 views
LDO transient performance enhancement circuit understanding
For the following LDO circuit, how does the transient performance enhancement circuit sub-block in green color works ?
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1answer
47 views
LDO peak-to-peak voltage 280mV
I have an LD1117V33 connected to a 12V powersupply. When I plug the output to my osciloscope I see about 280mv peak-to-peak voltage, sometime more.
Is it normal? Is there anything I can do to improve ...
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2answers
102 views
Rogue resistance between Vout and GND in LDO circuit
I'm currently developing a circuit as seen here:.
I had some suggestions to check my Iout to ensure that I wasn't drawing so much current that I was causing an overheat. After a little checking I ...
