MC34063A MC33063A
Figure 7. Step–Up Converter
170
µH
L
8
180
S Q
R
7
Ipk
Osc
6
+
100
VCC
+
– Comp.
5
R2
R1
2.2 k
47 k
330
+
CO
1.25 V
Ref
Reg
4
1.0
µH
Vout
28 V/175 mA
+
100
Vout
Q2
Q1
2
1N5819
Rsc
0.22
Vin
12 V
CT
3
CT
1500
pF
1
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
R
8
1
Vout
7
2
Rsc
7
2
Rsc
Vin
6
Vin
6
0 for
R
constant Vin
³
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
MOTOROLA [ MOTOROLA, INC ]
