I am working on a project using a 34063A step up converter to output ~18V (17.82 based on the math) from a "12V" vehicle power supply. Note the quotes around 12V... Data sheet for device is HERE
I have some concerns, I've gone over and over the data sheet and there are some things that confuse me, so I have some questions. I'd be very grateful if I got some input.
The data sheet says "Output switch current to 1.5A". If you look at page 5 at the test conditions there, all conditions are tested with 175mA. Does the output current allowed vary based on what your application is? I need right close to 240mA for my load.
Looking at R1 and R2 values for my desired output of near 18V, R1 = 2.49K and R2 = 33K. Are 1/4W resistors ok here? I know the P = I*E formula but I'm not sure how to determine what kind of voltages and currents these resistors would see.
The last problem I'm having in figuring out values & numbers is power dissipation. The data sheet says "maximum package power dissipation limits must be observed"... which I knew already, been down that road before. With an output voltage of 18V and device current needs at .240A, P=18*.240 = 4.32W? or am I using the wrong values to figure that one out (I have to assume I am). BTW, since max power dissipation values are different from package to package, my project is designed with the SOIC pack in mind.
I've come a long way in 6 months of getting into electronics, but not far enough yet apparently. Please help me!
All the best,
Ryan
I have some concerns, I've gone over and over the data sheet and there are some things that confuse me, so I have some questions. I'd be very grateful if I got some input.
The data sheet says "Output switch current to 1.5A". If you look at page 5 at the test conditions there, all conditions are tested with 175mA. Does the output current allowed vary based on what your application is? I need right close to 240mA for my load.
Looking at R1 and R2 values for my desired output of near 18V, R1 = 2.49K and R2 = 33K. Are 1/4W resistors ok here? I know the P = I*E formula but I'm not sure how to determine what kind of voltages and currents these resistors would see.
The last problem I'm having in figuring out values & numbers is power dissipation. The data sheet says "maximum package power dissipation limits must be observed"... which I knew already, been down that road before. With an output voltage of 18V and device current needs at .240A, P=18*.240 = 4.32W? or am I using the wrong values to figure that one out (I have to assume I am). BTW, since max power dissipation values are different from package to package, my project is designed with the SOIC pack in mind.
I've come a long way in 6 months of getting into electronics, but not far enough yet apparently. Please help me!
All the best,
Ryan