### Author Topic: 7805 regulator related Question  (Read 631 times)

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#### khatus

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##### 7805 regulator related Question
« on: January 22, 2019, 03:03:24 pm »

This is the datasheet of 7805 voltage regulator produced by "Continental Device India Limited"
My question is
2. What is Dropout Voltage??I know it's 2V But i want to know it's definition?
3. What is Quiescent Current and
4. Quiescent Current Change
5. Why peak output current is greater than Short Circuit Output Current?? The Short Circuit Output Current should be > peak output current since at short circuit resistance is zero and maximum current will flow??

#### imo

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##### Re: 7805 regulator related Question
« Reply #1 on: January 22, 2019, 03:27:12 pm »
It is a change of output voltage (delta_Vout) when changing the output current (delta_Iout)
2. What is Dropout Voltage??I know it's 2V But i want to know it's definition?
It is a minimal difference between the Vinput and Voutput such the regulator works reliably
3. What is Quiescent Current and
It is the current flowing off the regulator's GND pin (ie. to ground or elsewhere)
4. Quiescent Current Change
Is how the QCurr changes (delta_Iqc) when input voltage or output current changes by an amount.
5. Why peak output current is greater than Short Circuit Output Current?? The Short Circuit Output Current should be > peak output current since at short circuit resistance is zero and maximum current will flow??
Because the internal protection electronics needs some time to react accordingly (ie current limiting, temperature sensor).
« Last Edit: January 22, 2019, 03:31:24 pm by imo »

#### mvs

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##### Re: 7805 regulator related Question
« Reply #2 on: January 22, 2019, 03:38:52 pm »
2. What is Dropout Voltage??I know it's 2V But i want to know it's definition?
3. What is Quiescent Current and
4. Quiescent Current Change
5. Why peak output current is greater than Short Circuit Output Current?? The Short Circuit Output Current should be > peak output current since at short circuit resistance is zero and maximum current will flow??
1.-3. https://en.wikipedia.org/wiki/Voltage_regulator#Regulator_specification
4. Max change of quiescent current over specified junction temperature, input voltage and load current ranges.
5. This Vreg has built in short circuit current limiting protection.

#### Wolfgang

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##### Re: 7805 regulator related Question
« Reply #3 on: January 23, 2019, 09:18:19 pm »
You need to understand some electronics theory to get the meaning of datasheet values.
My recommendation: Art of Electronics by Horowitz and Hill.

#### khatus

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##### Re: 7805 regulator related Question
« Reply #4 on: February 01, 2019, 03:59:52 pm »
So at the time of theoretical calculation Which value(The peak value of current or short circuit output current) should i take as  maximum output current??

#### metrologist

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##### Re: 7805 regulator related Question
« Reply #5 on: February 01, 2019, 04:40:26 pm »
short circuit is a protection mode so limits the current. Use 2.2A as max possible output.

Smf