Author Topic: why no block diagram linear why u do dis  (Read 1549 times)

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Offline xReM1x

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why no block diagram linear why u do dis
« on: September 26, 2015, 07:25:16 pm »
http://cds.linear.com/docs/en/datasheet/1764afb.pdf
gimme my block diagram for this damn regulator
 

Offline Zero999

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Re: why no block diagram linear why u do dis
« Reply #1 on: September 26, 2015, 07:47:33 pm »
The detailed schematic will be proprietary information. The block diagram for low drop-out regulators is essentially the same: a voltage reference with an op-amp and a pass transistor in the feedback loop.

https://en.wikipedia.org/wiki/Low-dropout_regulator
www.analog.com/library/analogDialogue/archives/43-08/ldo.html

Normally, if the regulator has a positive output, the pass transistor will be P-channel/PNP. If the output is negative an N-channel/NPN transistor will be used. However it's possible to use an N-channel MOSFET on a positive output LDO but a voltage multiplier circuit is needed to bias the gate above the output.
 

Offline sarepairman2

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Re: why no block diagram linear why u do dis
« Reply #2 on: September 26, 2015, 07:54:51 pm »
lol why u stab me??
 

Offline xReM1x

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Re: why no block diagram linear why u do dis
« Reply #3 on: September 26, 2015, 08:52:08 pm »
The detailed schematic will be proprietary information. The block diagram for low drop-out regulators is essentially the same: a voltage reference with an op-amp and a pass transistor in the feedback loop.

https://en.wikipedia.org/wiki/Low-dropout_regulator
www.analog.com/library/analogDialogue/archives/43-08/ldo.html

Normally, if the regulator has a positive output, the pass transistor will be P-channel/PNP. If the output is negative an N-channel/NPN transistor will be used. However it's possible to use an N-channel MOSFET on a positive output LDO but a voltage multiplier circuit is needed to bias the gate above the output.
yes I know this, but how does they make it 340mV dropout at 3A and fast transiet response?
 

Online PeteH

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Re: why no block diagram linear why u do dis
« Reply #4 on: September 26, 2015, 09:20:39 pm »
Its likely a PNP output stage. The low drop out is just the Vce saturation curve of the bipolar transistor. The part operates at very low VIN, and you can see the ground pin current skyrocket at saturated or low VIN-VOUT. This gives away the fact that the part is pulling tons of base current out of the PNP to try and regulate the output while in and near saturation.
 

Online blueskull

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Re: why no block diagram linear why u do dis
« Reply #5 on: September 27, 2015, 03:23:04 am »
I stopped using LT parts for a year. Compared with TI or ADI, LT parts are very expensive and the documents are not as good/clear as the TI ones.

LT parts are good for mass production, I assume, because I have seen many teardowns featuring LT parts. But at low volume, they're are too expensive.
 


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