LM 3-terminal 1A Positive Voltage Regulator DESCRIPTION. The UTC LM78XX family is monolithic fixed voltage regulator integrated circuit. They are. lm are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for lm LM datasheet, LM circuit, LM data sheet: FAIRCHILD – 3- TERMINAL 1A POSITIVE VOLTAGE REGULATORS,alldatasheet, datasheet.
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On the datasheet it doesn’t mention an input voltage. A is a linear regulator, and does not step up the input voltage if the input is below the output for that you need a DC-DC boost regulator.
The input voltage must be above the output.
Dahasheet linear regulators have a minimum dropout voltageor difference. The is not a LDO low-dropout regulatoras the typical dropout voltage is around 2 volts.
An LDO might have a dropout voltage of 0.
On page 6 of the datasheet, the maximum dropout voltage Vd is listed as 2. Voltage regulators basically can be divided in two big groups: That means that when your load consumes 10W the switcher will only dissipate 1W. Linear regulators are different. They are like a variable series resistor between input and output, causing a voltage drop across the regulator. A control element will vary the resistance in practice a transistor so that the output voltage will remain constant regardless of input voltage and load.
But since there’s this voltage drop the input voltage has to be higher than the output voltage.
How much higher depends on the lm78100 of regulator. There are LDOs Low Drop-Out which still can regulate the output if the input is only a few hundreds of mV higher and there are even ultra low drop-out types which only need a few tens of mV.
The is a non-LDO dataseet regulator, which means it needs a higher input voltage. The datasheet does say how much it needs, but you may have to look for it. This is a snapshot lm78100 page All parameters are specified under certain conditions, and for the output voltage we can see that the condition is that the input voltage is minimum If we look further we can see two values for line regulation; it appears that this is best if the input voltage is at least 16V.
So you won’t find a parameter “minimum input voltage”, but it is mentioned as a condition for proper operation within certain limits.
LM datasheet & applicatoin notes – Datasheet Archive
A note on dissipation: From the above it may look like you best make your input voltage a lot higher than the 12V output, darasheet that’s not true. The current to your load flows through the regulator and is the same current as will be drawn from the input voltage.
So if you have a 12W load it will draw 1A from the regulator. If you have an input voltage of 20V the same 1A will be drawn from that 20V. So the 20V delivers 20W, while the load only consumes 12W. The difference of 8W will be dissipated in the regulator.
Therefore it’s best to keep the input voltage just above the minimum to prevent the regulator to become overheated.
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If so, what is the current like that it outputs? Peter Mortensen 1, 3 14 Dean 4, 22 57 From what i understand then from your answer How does it go from a Maximum dropout voltage to datasheeet minimum input voltage?
The maximum dropout voltage Vd is 2. Since the output is 12 volts, you add the two together to get a minimum input of Even though the typical dropout voltage is 2 volts, you should use the maximum value in your design. I’ve seen LDOs with a dropout voltage of 50 mV. This is a snapshot of page 8: Sign up or log in Sign up using Google. Sign up using Facebook.
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