MC33063A, MC34063A
1.5-A PEAK BOOST/BUCK/INVERTING SWITCHING REGULATORS
SLLS636J – DECEMBER 2004 – REVISED OCTOBER 2005
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R*
8
1
V
out
8
1
V
out
7
2
R
SC
7
2
R
SC
V
in
6
V
in
6
* R
"
0 for constant V
in
a) EXTERNAL npn SWITCH
b) EXTERNAL pnp SATURATED SWITCH (see Note A)
A.
If the output switch is driven into hard saturation (non-Darlington configuration) at low switch currents (≤300 mA) and
high driver currents (≥30 mA), it may take up to 2
µs
to come out of saturation. This condition will shorten the off time
at frequencies
≥30
kHz and is magnified at high temperatures. This condition does not occur with a Darlington
configuration because the output switch cannot saturate. If a non-Darlington configuration is used, the output drive
configuration in Figure 7b is recommended.
Figure 7. External Current-Boost Connections for I
C
Peak Greater Than 1.5 A
6
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