SG3525A SG3527A
Figure 7. SG3525A Output Circuit
(1/2 Circuit Shown)
VCC
Q5
Q7
Q9
Q4
Vref
Q6
2.0k
Q1
Q2
Q3
Q6 Omitted
in SG3527A
Q10
5.0k
Q8
11, 14
Output
Q11
13
VC
5.0k
Clock
F/F
10k
10k
PWM
Figure 8. Single–Ended Supply
Q1
+Vsupply
R1
R2
13
VC
SG3525A
B
Gnd
12
A
11
14
To Output Filter
Figure 9. Push–Pull Configuration
+Vsupply
R1
13
VC A
SG3525A
14
Gnd
B
R3
Q2
11
Q1
R2
C2
C1
T1
12
For single–ended supplies, the driver outputs are grounded.
The VC 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. Driving Power FETS
+Vsupply
Figure 11. Driving Transformers in a
Half–Bridge Configuration
+Vsupply
Q1
T1
T1
13
VC A
SG3525A
11
R1
Q2
14
C2
R2
T2
C1
R1
13
VC A
Q1
11
SG3525A
Gnd B
12
14
Q2
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.
6
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA, INC ]
