MC34063A Datasheet, PDF (5/12 Pages) ON Semiconductor – DC-to-DC CONVERTER CONTROL CIRCUITS

MC34063A MC33063A
Figure 7. Step–Up Converter
170 µH
8
180
7
Rsc
0.22
Vin
6
12 V
+
100
5
L
1
SQ
R
Q2
Q1
Ipk
CT
Osc
VCC
+
– ^Comp.
1.25 V
Ref
Reg
2
1N5819
3
CT
1500
pF
4
R2
47 k
R1 2.2 k
Vout
28 V/175 mA
+
330 CO
1.0 µH
Vout
+
100
Optional Filter
Test
Line Regulation
Load Regulation
Output Ripple
Efficiency
Output Ripple With Optional Filter
Conditions
Vin = 8.0 V to 16 V, IO = 175 mA
Vin = 12 V, IO = 75 mA to 175 mA
Vin = 12 V, IO = 175 mA
Vin = 12 V, IO = 175 mA
Vin = 12 V, IO = 175 mA
Results
30 mV = ±0.05%
10 mV = ±0.017%
400 mVpp
87.7%
40 mVpp
Figure 8. External Current Boost Connections for IC Peak Greater than 1.5 A
8a. External NPN Switch
8b. External NPN Saturated Switch
(See Note 5)
8
1
Vout
8
R
1
Vout
7
Rsc
Vin
6
7
2
Rsc
Vin
6
2
³ R 0 for
constant Vin
NOTE:
5. 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.
MOTOROLA ANALOG IC DEVICE DATA
5