L6668 STMicroelectronics, L6668 Datasheet

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... SO-16 in Tape & Reel ® VREG VREG 25V 25V Vref Vref Vcc_OK Vcc_OK DIS DIS 15V 15V VREG VREG DIS DIS 0.4mA 0.4mA STANDBY STANDBY SOFT-START SOFT-START COMP COMP L6668 Package SO- VREF VREF 4 4 OUT OUT 3 3 GND GND 13 13 ST-BY ST-BY Rev. 4 1/23 ...

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... L6668 2 Description L6668 is a current-mode primary controller IC, designed to build single-ended converters. The IC drives the system at fixed frequency at heavy load and an improved Standby function causes a smooth frequency reduction as the load is progressively reduced. At very light load the device enters a special operating mode (burst-mode with fixed, externally programmed peak current) that, in addition to the on-board high-voltage start-up and the very low quiescent current, helps keep low the consumption from the mains and be compliant with energy saving regulations ...

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... MOSFET. The pin is equipped with 200 ns. min. blanking time for improved noise immunity. A second comparison level located at 1.5V shuts the device down and brings its consumption almost to a “before start-up” level. Function L6668 3/23 ...

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... L6668 Table 4. Pin Description (continued) Pin Pin Name Number 13 STBY Standby function. This pin is a high-impedance one as long as the voltage on pin COMP is higher than 3V. When the voltage on pin COMP falls below 3V, the voltage on the pin tracks that on pin COMP and is capable of sinking current. A resistor connected from the pin to the oscillator allows programming frequency foldback at light load ...

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... V COMP Vcc = 9.4 to 22V COMP (2) ( kΩ to GND, S-COMP OUT pin high COMP kΩ to GND, S-COMP OUT pin high OUT pin low S-COMP S-COMPpk °C L6668 Min. Typ. Max. Unit 4.925 5 5.075 V 4.8 5. 0.2 0.5 V 5.5 V 320 400 480 µA kΩ ...

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... PWM is turned off in case of PFC's PWM is turned off in case of PFC's anomalous operation, for safety anomalous operation, for safety or or L6668 L6668 L6563 L6563 PFC can be turned off at light PFC can be turned off at light load to ease compliance with load to ease compliance with energy saving regulations ...

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... Values normalized 25°C HV 80% - 100 Tj (°C) 14 while 12 latched off 100 normal 6 operation 4 - 100 Tj (°C) 5 Operating 3 Quiescent 2 1 Disabled or Vcc = 15 V during burst-mode 100 kHz 0.5 0.3 Latched off 0.2 Before start-up (Vcc=12V) 0.1 - 100 Tj (°C) L6668 150 150 150 7/23 ...

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... L6668 Figure 11. Start-up & UVLO vs (pin 5) ( OFF while latched off OFF (°C) Figure 12. Vcc Zener voltage vs. Tj Vcc Z (pin (°C) Figure 13. COMP voltage upper clamp level vs (pin 10) COMP 7 (V) 6.5 6 5 (°C) 8/23 Figure 14. COMP source current vs COMP 100 150 Figure 15 ...

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... Tj (°C) REF (pin 8) 5.1 (V) Vcc = 15 V 5.05 5 4.95 4.9 - 100 Tj (°C) vs. Tj COMP (pin 10) 2.8 (V) PFC_STOP low (voltage rising) 2.7 2.6 Vcc = 15 V 2.5 2.4 2.3 PFC_STOP open (voltage falling) 2.2 2.1 - 100 Tj (°C) L6668 150 150 150 9/23 ...

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... L6668 Figure 23. Standby thresholds vs (pin 10) COMP 3.6 (V) 3.4 3.2 Disable (voltage rising) 3 Enable (voltage falling) 2.8 2.6 2.4 - (°C) Figure 24. Standby pin dropout vs. Tj Vpin13 - Vpin10 0 (mV) -5 -10 -15 -20 -25 -30 - (°C) Figure 25. DIS threshold vs pin 7 2.5 (V) 2.4 2.3 2.2 2.1 2.0 ...

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... Vcc - 2.0 Vcc - 3.0 Vcc - 4.0 Vcc - 5.0 Vcc - 6.0 100 150 Vcc = 20 V 100 150 [V] pin4 °C Vcc = 12 V SINK 0 200 400 600 800 1,000 1,200 I [mA [V] pin4 0 200 400 600 I [mA] GD L6668 °C Vcc = 12 V SOURCE 800 1,000 11/23 ...

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... L6668 4 Application Information The L6668 is a versatile current-mode PWM controller specific for offline fixed-frequency, peak-current- mode-controlled flyback converters. The device is able to operate in different modes (fig. 34), depending on the converter's load conditions: 1) Fixed frequency at heavy load. In this region the IC operates exactly like a standard current mode control chip: a relaxation oscillator, externally programmable with a capacitor and a resistor, generates a sawtooth and releases a clock pulse during the falling edge of the sawtooth ...

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... Vcc Vcc Vcc Vcc ON ON Vcc Vcc OFF OFF Vcc Vcc rest rest OUT OUT Vcc_OK Vcc_OK Normal Normal Power-up Power-up operation operation Short circuit occurs here Short circuit occurs here L6668 regulation is lost here regulation is lost here Power-down Power-down 13/23 ...

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... HV_EN is de-asserted instart ensures that, during short circuits, the restart attempts of the L6668 will ) is higher than 3V, the device works at a fixed COMP voltage falls below 3V (approximately corresponding to 50% of the COMP ...

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... V(SKIPADJ) = 1.5V V(SKIPADJ) = 1.5V 2.2V 2. V(SKIPADJ) = 1.4V V(SKIPADJ) = 1.4V 1.8V 1. STBY STBY specified. This value will be above the audible range to ensure a min to R for different values of the burst-mode threshold STBY T L6668 ratio as long as min osc /R ratio. STBY T /R ratio and STBY T 15/23 ...

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... L6668 Figure 40. Load-dependent operating modes: timing diagram COMP 3.0V V(SKIPADJ) f osc OUT Fix. Freq. Mode The operating range of the voltage V(SKIPADJ) is practically limited upwards by the onset of audible noise: typically, with a voltage above 2-2.1V some noise can be heard under some line/load conditions. If, instead, V(SKIPADJ) is set below the low saturation value of the PWM control voltage (1 ...

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... A capacitor (and a limiting resistor in the hundred ohms), shown in dotted lines, may be used if one wants to delay PFC turn-off When the L6668 is in UVLO (Vcc<8.7V) the pin is kept high ensure that the PFC pre-regulator will start up only after the DC-DC converter governed by the L6668 is activated. ...

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... L6668 Figure 43 shows a timing diagram where the PFC_STOP function operation is illustrated under different operating conditions. Figure 42. How the L6668 can switch off a PFC controller at light load L6668 L6668 Figure 43. Operation of PFC_STOP function Vcc Vcc ON Vcc OFF PFC_STOP COMP OUT PFC Gate Drive Figure 44 ...

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... Disable function Latched OTP or OVP functions can be easily realized with the L6668: the IC is equipped with a compara- tor whose non-inverting input is externally available on pin #7 (DIS), and whose inverting input is inter- nally referenced to 2.2V. As the voltage on the pin exceeds the threshold the IC is immediately shut down and its consumption re- duced at a low value ...

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... V 47 µF 47 µ 9.1 kΩ 9.1 kΩ VCC VCC DIS DIS HV HV R710Ω R710Ω OUT OUT R12 1kΩ R12 1kΩ ISEN ISEN L6668 L6668 COMP COMP GND GND OC1 OC1 C6 C6 PC817A PC817A R11 R11 2 kΩ 47 kΩ ...

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... OUTLINE AND MECHANICAL DATA SO16 (Narrow) 0016020 D L6668 ® pack- 21/23 ...

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... L6668 6 Revision History Table 7. Revision History Date Revision 20-May-2005 15-July-2005 28-July-2005 13-Jan-2006 22/23 1 First Issue. 2 Modify values in Electrical Characteristics 3 Changed the maturity from “Preliminary Data” to “Datasheet”. 4 Absolute Maximum Rating Update (added ESD note for pin 1). Modified value “DIS >2.2V” in the table 4 pin 14. ...

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