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PDF IL44608N Data sheet ( Hoja de datos )
| Número de pieza | IL44608N | |
| Descripción | External Components Reliable and Flexible SMPS Controller | |
| Fabricantes | IK Semicon | |
| Logotipo |  |
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TECHNICAL DATA
External Components Reliable and Flexible SMPS Controller
DESCRIPTION
The IL44608N is a high performance voltage mode controller designed
for off–line converters. This high voltage circuit that integrates the start–up
current source and the oscillator capacitor, requires few external components
while offering a high flexibility and reliability.
The device also features a very high efficiency stand–by management
consisting of an effective Pulsed Mode operation. This technique enables the
reduction of the stand–by power consumption to approximately 1.0 W while
delivering 300 mW in a 150 W SMPS.
● Integrated Start–Up Current Source
● Lossless Off–Line Start–Up
● Direct Off–Line Operation
● Fast Start–Up
IL44608N
General Features
● Flexibility
● Duty Cycle Control
● Under-voltage Lockout with Hysteresis
● On Chip Oscillator Switching Frequency 40, 75, or 100 kHz
● Secondary Control with Few External Components
Protections
● Maximum Duty Cycle Limitation
● Cycle by Cycle Current Limitation
● Demagnetization (Zero Current Detection) Protection
● “Over VCC Protection” Against Open Loop
● Programmable Low Inertia Over Voltage Protection against Open Loop
● Internal Thermal Protection
PACKAGE
PDIP-8
Pin Connection
SMPS Controller
● Pulsed Mode Techniques for a Very High Efficiency Low Power Mode
● Lossless Startup
● Low dV/dT for Low EMI Radiations
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Ordering Information
Device
IL44608N40
Switching Frequency
40 kHz
IL44608N75
75 kHz
IL44608N100
100 kHz
Package
Plastic
DIP–8
Plastic
DIP–8
Plastic
DIP–8
1
1 page  
OPERATING DESCRIPTION
The pin 3 senses the feedback current provided by the
opto coupler. During the switching phase the switch S2 is
closed and the shunt regulator is accessible by the pin 3.
The shunt regulator voltage is typically 5.0 V. The dy-
namic resistance of the shunt regulator represented by the
zener diode is 20 Ω. The gain of the Control input is given
on Figure 11/, which shows the duty cycle as a function of
the current injected into the pin 3.
A 4.0 kHz filter network is inserted between the shunt
regulator and the PWM comparator to cancel the high fre-
quency residual noise.
The switch S3 is closed in Stand–by mode during the
Latched Off Phase while the switch S2 remains open. (See
section PULSED MODE DUTY CYCLE CONTROL).
The resistor Rdpulsed (Rduty cycle burst) has no effect on
the regulation process. This resistor is used to determine
the burst duty cycle described in the chapter “Pulsed Duty
Cycle Control”
IL44608N
Current Sense
The inductor current is converted to a positive voltage
by inserting a ground reference sense resistor RSense in se-
ries with the power switch.
The maximum current sense threshold is fixed at 1.0 V.
The peak current is given by the following equation:
Ipk max
=
1
R SENSE (Ω)
(A)
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In stand–by mode, this current can be lowered as due
activation of a 200 µA current source:
Ipk
max − stby
=
1-
(R cs (k Ω ) × 0,2)
R SENSE ( Ω )
(A)
PWM Latch
The IL44608 works in voltage mode. The on–time is
controlled by the PWM comparator that compares the os-
cillator sawtooth with the regulation block output (refer to
the block diagram on page 2).
The PWM latch is initialized by the oscillator and is re-
set by the PWM comparator or by the current sense com-
parator in case of an over current. This configuration en-
sures that only a single pulse appears at the circuit output
during an oscillator cycle.
The current sense input consists of a filter (6.0 k Ω, 4.0
pF) and of a leading edge blanking. Thanks to that, this pin
is not sensitive to the power switch turn on noise and
spikes and practically in most applications, no filtering
network is required to sense the current.
Finally, this pin is used:
– as a protection against over currents (Isense > I)
– as a reduction of the peak current during a Pulsed
Mode switching phase.
The overcurrent propagation delay is reduced by produc-
ing a sharp output turn off (high slew rate). This results in
an abrupt output turn off in the event of an over current
and in the majority of the pulsed mode switching sequence.
5
5 Page 
IL44608N
Figure 9. Output Switching Speed
Figure 10. Frequency Stability
The data in Figure 9 corresponds to the waveform in Figure 10. The Figure 10 shows VCC, ICC, Isense (pin 2) and Vout
(pin 5). Vout (pin 5) in fact shows the envelope of the output switching pulses. This mode corresponds to an overload con-
dition.
The secondary reconfiguration is activated by the mP 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 thy-
ristor gate (switch open) thus firing the MCR22–6. The closed position of the switch corresponds to the Pulsed Mode acti-
vation. 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
The Figure 11 shows the SMPS behavior while working in the reconfigured mode. The top curve represents the VCC
voltage (pin 6 of the IL44608). 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 applied to the sec-
ondary 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 cho-
sen higher than the normal mode regulation level. This working mode creates a voltage ripple on the 8.0 V rail which gen-
erally 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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Figure 11. SMPS Pulsed Mode
11
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