Figure 10 and 11 of MC34063A datasheet

mankun Li

Other Parts Discussed in Thread: MC34063A

Figure 10 and 11, these 2 application seems impossible, since during internal switch off, the SW point is at negative level(Vout-Vd), the base of Q1 and Q2 should be kept no 0.7V higher above that negative level, which seems impossible for the chip to be. Figure 12 is the feasible application of the inverting convert setup. Would TI conside update the datasheet.

over 13 years ago

0 Ron Michallick over 13 years ago

TI__Guru**** 165126 points

Mankun,

Note that on page 9, figure 10 and 11 connect the MC34063A ground pin to Vout.
Therefore the base of Q2 can go as low as Vout (-12V in this application).

0 mankun Li over 13 years ago in reply to Ron Michallick

Prodigy 20 points

Oho, yes, i just noticed the chip's pin 4(GND) connecting to the negaive rail(Vout) of voltage inverting setup as it should be to use the inner comparator, then the applications(figure 10, 11, 12) are all feasible.

Thanks,

Mankun Li

Power management

Power management forum

Figure 10 and 11 of MC34063A datasheet