SG3525A Datasheet, PDF (6/8 Pages) Motorola, Inc – PULSE WIDTH MODULATOR CONTROL CIRCUITS

SG3525A SG3527A
Figure 7. SG3525A Output Circuit
(1/2 Circuit Shown)
VCC
Q5
Q7
Q9
13
VC
Q10
Q4
5.0k
Vref
Q8
Q6
11, 14
Q11 ^Output
2.0k
Q1
Q2
Q3
Q6 Omitted
in SG3527A
5.0k
10k
10k
Clock F/F
PWM
Figure 8. Single–Ended Supply
+Vsupply
Q1
To Output Filter
R1
R2
13
VC 11
A
SG3525A ₁₄
B
Gnd
12
Figure 9. Push–Pull Configuration
+Vsupply
R1
C1
13
VC _A ¹¹
Q1
T1
R2
SG3525A
C2
14
B
Q2
Gnd
R3
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
R1
13 ₁₁ Q1
T1
VC A
SG3525A
Q2
14
Gnd ^B
12
Figure 11. Driving Transformers in a
Half–Bridge Configuration
+Vsupply
T1
13
11
VC A
SG3525A
14
Gnd ^B
12
Q1
R1
Q2
R2
C1
T2
C2
The low source impedance of the output drivers provides
rapid charging of power FET input capacitance while
minimizing external components.
6
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.
MOTOROLA ANALOG IC DEVICE DATA