Electronics > Beginners

Linear Technology LT1963 1.5A LDO - Output current no more than 100mA!

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Nerull:
That's a SO-8 package, and its rated at about 70C/W, if it has 2500mm^2 of copper heatsinking on the board.

That little breakout board is not going to put out 1.2A.

hgg:
Yes sorry, SO8.
The breakout is only for testing.
When I finish the prototype I am going to design a small 30x25mm pcb.
Is it possible?...

David Hess:
It may also be oscillating with the capacitors so far away.  Move the capacitor connections to a spot immediately adjacent to the regulator or even solder them onto the interposer.

hgg:
I've managed to get 800mA.  Its the breadboard.  Genuine Chiniseum.
The trace on the oscilloscope is completely flat with non existent ripple or spikes even in the 2mV range.

hgg:
I have another problem... :palm:

I have connected the FDS6898A N-Channel MOSFET in the circuit as in the schematic below :



The 2.6V output of the LDO is very stable but when I connect the gate of the MOSFET to the 2.6V rail,
the 2.6V rail becomes a 3.2V rail... :)

Its like something is changing the ADJ pin voltage divider.
Normally I measure the ADJ pin at 1.1V and when I connect the gate of the MOSFET directly to
the 2.6V rail, I measure 1.4V on the ADJ pin.


What am I doing wrong?

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