MC44608P100 ON Semiconductor, MC44608P100 Datasheet - Page 7

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

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

Figure 6. The Clock signals correspond to the CT capacitor
discharge. The bottom curve represents the current flowing
in the sense resistor Rcs. It starts from zero and stops when
the sawtooth value is equal to the control voltage Vcont. In
this way the SMPS is regulated with a voltage mode control.
Overvoltage Protection
15.4 V
current flowing into the demag pin is mirrored and
compared to the reference current Iovp (120 mA). Thus this
OVP is quicker as it is not impacted by the V
is called QOVP.
output is latched off until a new circuit START−UP.
Start−up Management
This high voltage current source is internally connected to
the V
V
phase. When the V
9.0 mA current source is disabled and the device starts
working. The device enters into the switching phase.
is 500 V. ESD protection circuitry is not currently added to
this pin due to size limitations and technology constraints.
Protection is limited by the drain−substrate junction in
avalanche breakdown. To help increase the application
safety against high voltage spike on that pin it is possible to
insert a small wattage 1.0 kW series resistor between the V
rail and pin 8.
no external current source providing current into the V
pin during the switching phase. This case can be
encountered in SMPS when the self supply through an
auxiliary winding is not present (strong overload on the
SMPS output for example). The Figure 17 also depicts this
working configuration.
Vcont
Clock
2.4 V
DMG
Iprim
OSC
CC
4 V
The OSC and Clock signals are provided according to the
The MC44608 offers two OVP functions:
− a fixed function that detects when V
− a programmable function that uses the demag pin. The
In both cases, once an OVP condition is detected, the
The V
It is to be noticed that the maximum rating of the V
The Figure 7 shows the V
CC
capacitor charge period corresponds to the Start−up
i
pin and thus is used to charge the V
pin 8 is directly connected to the HV DC rail Vin.
CC
voltage reaches 13 V, the high voltage
Figure 6.
CC
voltage evolution in case of
CC
CC
is higher than
CC
capacitor. The
inertia and
http://onsemi.com
i
pin 8
CC
MC44608
in
7
phase is in the range of 10%.
Mode Transition
at the end of every switching sequence.
termination of the SWITCHING PHASE:
NOC in case of “No Over Current” and “OC” in case of Over
Current. So the effective working status at the end of the ON
time memorized in LW corresponds to Q=1 for no over
current and Q=0 for over current.
electrolithic bulk capacitor provides energy to the SMPS,
the controller remains in the switching phase. Then the peak
current reaches its maximum peak value, the switching
frequency decreases and all the secondary voltages are
reduced. The V
equal to 10 V, the SMPS stops working.
VPWM
LEB out
In case of the hiccup mode, the duty cycle of the switching
The LW latch Figure 8 is the memory of the working status
Two different cases must be considered for the logic at the
1. No Over Current was observed
2. An Over Current was observed
These 2 cases are corresponding to the signal labelled
This sequence is repeated during the Switching phase.
Several events can occur:
1. SMPS switch OFF
2. SMPS output overload
3. Transition from Normal to Pulsed Mode
4. Transition from Pulsed Mode to Normal Mode
When the mains is switched OFF, so long as the bulk
Start−up
OUT
1. SMPS SWITCH OFF
Phase
V
1 V
CC
+
−
&
CS
NOC
OC
Figure 8. Transition Logic
CC
Figure 7. Hiccup Mode
R
S
LW
voltage is also reduced. When V
Start−up
Q
Q
Phase
Latched Off
Latched off
Phase
Phase
&
&
> 24 A
I
demag
m
Mode
R1
R2
S
Switching
Q
Phase
Stand−by
&
Start−up
Phase
Switching
Phase
6.5 V
13 V
10 V
Switch
CC
S1
is