SG3525A
http://onsemi.com
7
Figure 9. Output Circuit
(1/2 Circuit Shown)
Figure 10. Single−Ended Supply Figure 11. Push−Pull Configuration
Figure 12. Driving Power FETS
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.
Q1
R1
R2
13
To Output Filter
11
14
12
V
C
SG3525A
A
B
GND
+
V
supply
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.
V
C
SG3525A
A
B
GND
+V
supply
R1
13
12
11
14
R3
C2
C1
Q1
Q2
T1
R2
The low source impedance of the output drivers provides
rapid charging of power FET input capacitance while
minimizing external components.
+
V
supply
V
C
SG3525A
A
B
GND
11
14
Q1
Q2
T1
R1
13
12
V
C
SG3525A
A
B
GND
13
11
14
12
+V
supply
T1
Q1
Q2
R2
R1
T2
C1
C2
Figure 13. Driving Transformers in a
Half−Bridge Configuration
Q3
V
CC
Q5
Q4
Q7
Q9
Q10
13
V
C
V
ref
Q1 Q2
Q6 Omitted
in SG3527A
5.0k 10k 10k
2.0k
Q11
Q6
Q8
5.0k
11, 14
Output
Clock F/F PWM
