SG3525A
V
CC
Q5
Q7
Q9
Q4
V
ref
Q6
2.0k
Q1
Q2
Q3
Q6 Omitted
in SG3527A
Q10
5.0k
Q8
11, 14
Output
Q11
13
V
C
5.0k
Clock
F/F
10k
10k
PWM
Figure 9. Output Circuit
(1/2 Circuit Shown)
Q1
+
V
supply
To Output Filter
R1
R2
13
V
C
SG3525A
B
GND
12
A
11
14
+V
supply
R1
13
V
C
A
SG3525A
14
GND
B
R3
Q2
11
Q1
R2
C2
C1
T1
12
For single−ended supplies, the driver outputs are grounded.
The V
C
terminal is switched to ground by the totem−pole
source transistors on alternate oscillator cycles.
In conventional push−pull bipolar designs, forward base drive is
controlled by R1−R3. Rapid turn−off times for the power devices
are achieved with speed−up capacitors C1 and C2.
Figure 10. Single−Ended Supply
Figure 11. Push−Pull Configuration
+
V
supply
R1
13
V
C
A
Q1
T1
+V
supply
Q1
T1
13
V
C
A
SG3525A
14
Q2
GND B
12
14
C2
R2
11
R1
Q2
T2
C1
11
SG3525A
GND B
12
The low source impedance of the output drivers provides
rapid charging of power FET input capacitance while
minimizing external components.
Low power transformers can be driven directly by the SG3525A.
Automatic reset occurs during deadtime, when both ends of the
primary winding are switched to ground.
Figure 12. Driving Power FETS
Figure 13. Driving Transformers in a
Half−Bridge Configuration
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