MC34063 Datasheet, PDF (6/16 Pages) ON Semiconductor – DC-to-DC Converter Control Circuits

8
7
R_sc
V_in
6
MC34063A, MC33063A
1
V_out
8
7
2
R_sc
V_in
6
R
1
V_out
2
R ³ 0 for
constant V_in
Figure 8. External Current Boost Connections for I_C Peak Greater than 1.5 A
8a. External NPN Switch
8b. External NPN Saturated Switch
(See Note 7.)
7. 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 2.0 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, since the output switch cannot saturate. If a
non–Darlington configuration is used, the following output drive condition is recommended.
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