Apart from using it as a voltage regulator it can also be used as a current regulator, short-circuit protector, booster circuit and even a variable voltage regulator. The circuits for all these applications can be found at page 27/45 in the 78L05 datasheet given below.
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78l05 smd datasheet pdf 11
Needless to say, at the heart of the module is a XL4015 chip from XLSEMI (www.xlsemi.com) which is a 180 KHz fixed frequency PWM step-down (buck) DC/DC converter, capable of driving a 5A load with high efficiency, low ripple and excellent line and load regulation. According to its datasheet (Rev 1.5) the PWM control circuit can adjust the duty ratio linearly from 0 to 100%. An over current protection function is built inside so that when a short circuit occurs, the operation frequency will be reduced to 48KHz. Below you can see the function block diagram of XL4015 (XL4015E1).
Everything has a tolerance. See the oscillogram taken while my DSO was probed at Pin 3 of XL4015. The switching frequency (Fosc) is about 190kHz. According to the datasheet, this lies in 144-216kHz range (180kHz typical). The output ripple is 18mV. Not bad at all! 2ff7e9595c
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