MC44608P100 ON Semiconductor, MC44608P100 Datasheet - Page 14

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MC44608P100

Manufacturer Part Number
MC44608P100
Description
IC PWM FLYBCK ISO VM 8DIP
Manufacturer
ON Semiconductor
Datasheet

Specifications of MC44608P100

Pwm Type
Voltage Mode
Number Of Outputs
1
Frequency - Max
110kHz
Duty Cycle
86%
Voltage - Supply
6.6 V ~ 13 V
Buck
No
Boost
No
Flyback
Yes
Inverting
No
Doubler
No
Divider
No
Cuk
No
Isolated
Yes
Operating Temperature
-25°C ~ 85°C
Package / Case
8-DIP (0.300", 7.62mm)
Frequency-max
110kHz
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
MC44608P100OS
through the switch. The dV/dt appearing on the high voltage
winding (pins 14 of the transformer) at every TMOS switch
off, produces a current spike through the series RC network
R7, C17. According to the switch position this spike is either
absorbed by the ground (switch closed) or flows into the
thyristor gate (switch open) thus firing the MCR22−6. The
closed position of the switch corresponds to the Pulsed
Mode activation. In this secondary side SMPS status the
high voltage winding (12−14) is connected through D12 and
DZ1 to the 8.0 V low voltage secondary rail. The voltages
in the reconfigured mode. The top curve represents the V
voltage (pin 6 of the MC44608). The middle curve
represents the 8.0 V rail. The regulation is taking place at
11.68 V. On the bottom curve the pin 2 voltage is shown.
This voltage represents the current sense signal. The pin 2
The secondary reconfiguration is activated by the mP
The Figure 19 shows the SMPS behavior while working
Figure 19. SMPS Pulsed Mode
http://onsemi.com
CC
MC44608
14
applied to the secondary windings 12−14, 10−11 and 6−7
(Vaux) are thus divided by ratio N12−14 / N9−8 (number of
turns of the winding 12−14 over number of turns of the
winding 9−8). In this reconfigured status all the secondary
voltages are lowered except the 8.0 V one. The regulation
during every pulsed or burst is performed by the zener diode
DZ3 which value has to be chosen higher than the normal
mode regulation level. This working mode creates a voltage
ripple on the 8.0 V rail which generally must be post
regulated for the microProcessor supply.
voltage is the result of the 200 mA current source activated
during the start−up phase and also during the working phase
which flows through the R4 resistor. The used high
resolution mode of the oscilloscope does not allow to show
the effective ton current flowing in the sensing resistor R11.

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