Debug LM1117 voltage Conversion chip __lm1117

LM1117 (not LM117) power supply chip is a low-voltage differential linear regulator, referred to as LDO(Low dropout regulator), is a non-isolated (input and output voltage of the ground is a place) of the voltage conversion chip. Therefore, in the use of the time, as far as possible to the output voltage and input voltage pressure difference not too large, if too large, the consequences should be a serious chip fever. The maximum contact pressure difference is 15 to 3.3V.

The output current of the LM1117 chip is the maximum output current 800ma, so it needs to be considered when used. If the current is too large, it will pull down the chip output voltage, leading to the failure of the voltage regulator.

The pins of the chip below are (adj is the 1,ouput is the 2,input is the 3,tab is V is 4)

The typical application circuit of the non adjustable chip is (adjustable chip modification method is)

The circuit of an adjustable chip

But the one thing to note in the adjustable circuit is that the R1 range is typically 100 to 200 euro.

Note that the Lm1117-adj output voltage range is 1.25v-13.8v, does not mean that the adj end of the resistance, or to allow the R0 to the time the output is 1.25V, the output of 1.25V circuit should be as follows (r1=220,r2=0):

The adjustable 1117 and the output fixed voltage of the 1117 circuit is compatible with the PIN, the peripheral circuit resistance adjustment is as follows (R1, r2=0):

When disconnected from the circuit connection, the Adj version of the partial voltage resistor set to 2k,2k, found that the output voltage is not calculated, 5v out of the voltage is 4v, when the load circuit connected, the voltage back to normal, but high voltage, Is 2.6v, the load circuit's resistance value is about 9.35k, therefore, here to want accurate calculation value, resistance R2 Select Small point is a key.

Relative to lm317/lm117, output current 1.5A, output voltage can be continuously adjustable between 1.25~37v, the connection method is like Figure 19, but R1 current is less than 3.5mA. As for the data manual on the chip can provide more than 1.5A of the current argument, is this, in the input and output of the voltage difference multiplied by the current power under 2 W, can not add the radiator, if it is greater than 2W less than 15W need to add 200x200x4mm3 heatsink Board

Adjustable chip output voltage adjustable range in the 1.25v-13.8v package form has the following several:

So, the only thing that can add a heatsink is TO-220. Because there is overheating inside the chip protection, so in other packages, if the power consumption on the chip to 2W (as the case) above, the chip will occasionally appear thermal protection, the outside performance is the power of the ripple change is very large. So this situation, individuals think can also be tried with LM1117.