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.
●I ntegrated Start–Up Current Source
●L ossless Off–Line Start–Up
●D irect Off–Line Operation
●F ast Start–Up
General Features
●F lexibility
●D uty Cycle Control
●U nder-voltage Lockout with Hysteresis
●O n Chip Oscillator Switching Frequency 40, 75, or 100 kHz
●S econdary Control with Few External Components
Protections
●M aximum Duty Cycle Limitation
●C ycle by Cycle Current Limitation
●D emagnetization (Zero Current Detection) Protection
●“Over VCC Protection” Against Open Loop
●P rogrammable Low Inertia Over Voltage Protection against Open Loop
●I nternal Thermal Protection
SMPS Controller
●P ulsed Mode Techniques for a Very High Efficiency Low Power Mode
●L ossless Startup
●L ow dV/dT for Low EMI Radiations
Ordering Information
Device Switching
Frequency
Package
IL44608N40 40
kHz Plastic DIP–8
IL44608N75 75
kHz Plastic DIP–8
IL44608N100 100
kHz Plastic DIP–8
PIN FUNCTION DESCRIPTION
Pin Symbol Function
1 Demag The Demag pin offers 3 different functions: Zero voltage crossing detection (50 mV), 24 µA cur-rent detection and 120 µA current detection. The 24 µA level is used to detect the secondary re-configuration status and the 120 µA level to detect an Over Voltage status called Quick OVP.
2 Isense
The Current Sense pin senses the voltage developed on the series resistor inserted in the source of the power MOSFET. When Isense reaches 1.0 V, the Driver output (pin 5) is disabled. This is known as the Over Current Protection function. A 200 µA current source is flowing out of the pin
3 during the start–up phase and during the switching phase in case of the Pulsed Mode of opera-tion. A resistor can be inserted between the sense resistor and the pin 2, thus a programmable peak current detection can be performed during the SMPS stand–by mode.
3 Control Input
A feedback current from the secondary side of the SMPS via the opto–coupler is injected into this
pin. A resistor can be connected between this pin and GND to allow the programming of the
Burst duty cycle during the Stand–by mode.
4 Ground This pin is the ground of the primary side of the SMPS.
5 Driver The current and slew rate capability of this pin are suited to drive Power MOSFETs.
6 V ССThis pin is the positive supply of the IC. The driver output gets disabled when the voltage be-comes higher than 15 V and the operating range is between 6.6 V and 13 V. An intermediate
voltage level of 10 V creates a disabling condition called Latched Off phase.
7 This pin is to provide isolation between the V i pin 8 and the V CC pin 6.
8 V i This pin can be directly connected to a 500 V voltage source for start–up function of the IC. Dur-ing the Start–up phase a 9.0 mA current source is internally delivered to the V CC pin 6 allowing a
rapid charge of the V CC capacitor. As soon as the IC starts–up, this current source is disabled.
Figure 1. Representative Block Diagram
MAXIMUM RATINGS
Rating Symbol
Value
Unit Total Power Supply Current I CC30 mA
Output Supply Voltage with Respect to Ground V CC16 V
All Inputs except Vi V inputs–1.0 to +16 V
Line Voltage Absolute Rating V i500 V
Recommended Line Voltage Operating Condition V i400 V
Power Dissipation and Thermal Characteristics
Maximum Power Dissipation at TA = 85°C Thermal Resistance, Junction–to–Air
P D
R QJA
600
100
mV
ºC/W
Operating Junction Temperature T J150 ºC
Operating Ambient Temperature T A–25 to +85 ºC
ELECTRICAL CHARACTERISTICS(V CC = 12 V, for typical values T A = 25°C, for min/max values T A = –25°C to +85°C unless otherwise
noted)
Characteristic Symbol
Min
Typ
Max
Unit OUTPUT SECTION
Output Resistor
Sink Resistance Source Resistance ROL
ROH
5.0
-
8.5
15
15
-
Ω
Output Voltage Rise Time (from 3.0 V up to 9.0 V) (Note 1.) t r- 50 - ns Output Voltage Falling Edge Slew–Rate (from 9.0 V down to 3.0 V)
(Note 1.)
t f- 50 - ns CONTROL INPUT SECTION
Duty Cycle @ I pin3 = 2.5 mA d2mA- - 2.0 % Duty Cycle @ I pin3 = 1.0 mA d1mA36 - 48 % Control Input Clamp Voltage (Switching Phase) @ I pin3 = –1.0 mA 4.75 - 5.25 V Latched Phase Control Input Voltage (Stand–by) @ I pin3 = +500 _A V LP–stby 3.4 - 4.3 V Latched Phase Control Input Voltage (Stand–by) @ I pin3 = +1.0 mA V LP–stby 3.4 - 3.7 V CURRENT SENSE SECTION
Maximum Current Sense Input Threshold V CS–th0.95 - 1.05 V Input Bias Current I B–cs-1.8 - 1.8 µA Stand–By Current Sense Input Current I CS–stby180 - 220 µA Start–up Phase Current Sense Input Current I CS–stup180 - 220 µA
Propagation Delay (Current Sense Input to Output @ V TH T MOS = 3.0 V) Leading Edge Blanking Duration IL44608N40 T PLH(In/Out)
T LEB
-
-
220
480
-
-
ns
ns
Leading Edge Blanking Duration IL44608N75 T LEB- 250 - ns Leading Edge Blanking Duration IL44608N100 T LEB- 200 - ns Leading Edge Blanking + Propagation Delay IL44608N40 T DLY500 - 900 ns Leading Edge Blanking + Propagation Dela
y IL44608N75 T DLY370 - 570 ns Leading Edge Blanking + Propagation Delay IL44608N100 T DLY300 - 500 ns OSCILLATOR SECTION
Normal Operation Frequency IL44608N40 f osc36 - 44 kHz Normal Operation Frequency IL44608N75 f osc68 - 82 kHz Normal Operation Frequency IL44608N100 f osc90 - 110 kHz Maximum Duty Cycle @ f = f osc d max78 - 86 % OVERVOLTAGE SECTION
Quick OVP Input Filtering (R demag = 100 k Ω) T filt- 250 - ns Propagation Delay (I demag > I ovp to output low) T PHL(In/Out)- 2.0 - µs Quick OVP Current Threshold I OVP105 - 140 µA Protection Threshold Level on V CC V CC–OVP14.8 - 15.8 V Minimum Gap Between V CC–OVP and V stup–th V CC–OVP – V stup 1.0 - - V NOTE 1: This parameter is measured using 1.0 nF connected between the output and the ground.
ELECTRICAL CHARACTERISTICS(V CC = 12 V, for typical values T A = 25°C, for min/max values T A = –25°C to +85°C unless otherwise
noted) (Note2 )
Characteristic Symbol
Min
Typ
Max
Unit DEMAGNETIZATION DETECTION SECTION (Note 3.)
Demag Comparator Threshold (V pin1 increasing) V dmg–th30 - 69 mV
Demag Comparator Hysteresis (Note 4.) H dmg- 30 - mV
Propagation Delay (Input to Output, Low to High) t PHL(In/Out)- 300 - ns
Input Bias Current (V demag = 50 mV) I dem–lb-0.6 - - µA
Negative Clamp Level (I demag = –1.0 mA) V cl–neg–dem-0.9 - -0.4 V
Positive Clamp Level @ I demag = 125 µA V cl–pos–
dem–H
2.05 - 2.8 V
Positive Clamp Level @ I demag = 25 µA V cl–pos–
dem–L
1.4 - 1.9 V
OVERTEMPERATURE SECTION
Trip Level Over Temperature T high- 160 - ºC Hysteresis T hyst- 30 - ºC STAND–BY MAXIMUM CURRENT REDUCTION SECTION
Normal Mode Recovery Demag Pin Current
Threshold Idem–NM 20 - 30 µA K FACTORS SECTION FOR PULSED MODE OPERATION
I CCS / I stup IL44608N40 10 x K1 2.4 - 3.8 - I CCS / I stup IL44608N75 10 x K1 2.8 - 4.2 - I CCS / I stup IL44608N100 10 x K1 3.1 - 4.5 - I CCL / I stup103 x K246 - 63 - (V stup – U
VLO2) / (V stup – UVLO1) 102 x K sstup 1.8 - 2.6 - (UVLO1 – UVLO2) / (V stup – UVLO1) 102 x K sl90 - 150 - I CS / V csth106 x Y cstby175 - 225 - Demag ratio I ovp / I dem NM Dmgr 3.0 - 5.5 - (V3 1.0 mA – V3 0.5 mA) / (1.0 mA – 0.5 mA) R3 - 1800 - Ω
V control Latch–off V3 - 4.8 - V SUPPLY SECTION
Minimum Start–up Voltage V ilow- - 50 V V CC Start–up Voltage V stup–th12.5 - 13.8 V Output Disabling VCC Voltage After Turn On V uvlo19.5 - 10.5 V Hysteresis (V stup–th – V uvlo1) H stup–uvlo1- 3.1 - V V CC Undervoltage Lockout Voltage V uvlo2 6.2 - 7.0 V Hysteresis (V uvlo1 – V uvlo2) H uvlo1–uvlo2- 3.4 - V Absolute Normal Condition V CC Start Current @ (V i = 100 V) and
(V CC = 9.0 V)
–(I CC) 7.0 - 12.8 mA Switching Phase Supply Current (no load) IL44608N40
IL44608N75 IL44608N100 I CCS
2.0
2.4
2.6
-
-
-
3.6
4.0
4.5
mA
Latched Off Phase Supply Current I CC–latch0.3 - 0.68 mA Hiccup Mode Duty Cycle (no load) _H iccup- 10 - % CC
temperature as close to ambient as possible.
NOTE 3 : This function can be inhibited by connecting pin 1 to GND.
NOTE 4 : Guaranteed by design (non tested).
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”
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 pag
e 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.
Current Sense
The inductor current is converted to a positive voltage by inserting a ground reference sense resistor R Sense 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:
)A (R 1Ipk )
( SENSE max Ω=
In stand–by mode, this current can be lowered as due activation of a 200 µA current source:
(A)
)(R 0,2))(k (R -1Ipk SENSE cs stby max Ω×Ω=−
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.
Demagnetization Section
The IL44608N demagnetization detection consists of a comparator designed to compare the V CC winding voltage
to a reference that is typically equal to 50 mV.
This reference is chosen low to increase effectiveness of the demagnetization detection even during start–up.
A latch is incorporated to turn the demagnetization block output into a low level as soon as a voltage less than 50 mV is detected, and to keep it in this state until a new pulse is generated on the output. This avoids any ringing on the input signal which may alter the demagnetization detection.
For a higher safety, the demagnetization block output is also directly connected to the output, which is disabled during the demagnetization phase.
The demagnetization pin is also used for the quick, pro-grammable OVP. In fact, the demagnetization input cur-rent is sensed so that the circuit output is latched off when this current is detected as higher than 120 µA .
This function can be inhibited by grounding it but in this case, the quick and programmable OVP is also dis-abled.
Oscillator
The IL44608 contains a fixed frequency oscillator. It is built around a fixed value capacitor CT succes-sively charged and discharged by two distinct current sources ICH and IDCH. The window comparator senses the CT voltage value and activates the sources when the voltage is reaching the 2.4 V/4.0 V levels.
The complete demagnetization status DMG is used to inhibit the recharge of the CT capacitor. Thus in case of incomplete transformer demagnetization the next switch-ing cycle is postpone until the DMG signal appears. The oscillator remains at 2.4 V corresponding to the sawtooth valley voltage. In this way the SMPS is working in the so called SOPS mode (Self Oscillating Power Supply). In that case the effective switching frequency is variable and no longer depends on the oscillator timing but on the external working conditions (Refer to DMG signal in the Figure 6)
The OSC and Clock signals are provided according to the Figure 6. The Clock signals correspond to the CT capacitor discharge. The bottom curve represents the cur-rent 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.
