 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
FSQ510M Datasheet(PDF) 10 Page - Fairchild Semiconductor |
|
||||||||||||||||||||||||||||||
FSQ510M Datasheet(HTML) 10 Page - Fairchild Semiconductor |
|
|
10 / 15 page  © 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com FSQ510, FSQ510H, and FSQ510M • Rev. 1.3.0 10 4. Protection Circuits : The FSQ510 (H or M) has two self-protective functions, overload protection (OLP) and thermal shutdown (TSD). The protections are implemented as auto-restart mode. Once the fault condition is detected, switching is terminated and the SenseFET remains off. This causes VCC to fall. When V B CC B falls down to the under-voltage lockout (UVLO) stop voltage of 6.7V, the protection is reset and the startup circuit charges the VCC capacitor. When VCC reaches the start voltage of 8.7V, the FSQ510 (H or M) resumes normal operation. If the fault condition is not removed, the SenseFET remains off and VCC drops to stop voltage again. In this manner, the auto-restart can alternately enable and disable the switching of the power SenseFET until the fault condition is eliminated. Because these protection circuits are fully integrated into the IC without external components, reliability is improved without increasing cost. Fault situation 6.7V 8.7V VCC Vds t Fault occurs Fault removed Normal operation Normal operation Power on Figure 16. Auto Restart Protection Waveforms 4.1 Overload Protection (OLP) : Overload is defined as the load current exceeding its normal level due to an unexpected event. In this situation, the protection circuit should trigger to protect the SMPS. However, even when the SMPS is in the normal operation, the overload protection circuit can be triggered during the load transition. To avoid this undesired operation, the overload protection circuit is designed to trigger only after a specified time to determine whether it is a transient situation or a true overload situation. Because of the pulse-by-pulse current limit capability, the maximum peak current through the SenseFET is limited and, therefore, the maximum input power is restricted with a given input voltage. If the output consumes more than this maximum power, the output voltage (Vo) decreases below the set voltage. This reduces the current through the opto-coupler LED, which also reduces the opto-coupler transistor current, increasing the feedback voltage (VFB). If VFB exceeds 2.8V, D1 is blocked and the 5µA current source starts to charge CB slowly up. In this condition, VFB continues increasing until it reaches 4.7V, when the switching operation is terminated, as shown in Figure 17. The delay time for shutdown is the time required to charge CB from 2.8V to 4.7V with 5µA. A 20 ~ 50ms delay time is typical for most applications. This protection is implemented in auto-restart mode. VFB t 2.8V 4.7V Overload Protection t12= CB•(4.7-2.8)/Idelay t1 t2 Figure 17. Overload Protection 4.2 Thermal Shutdown (TSD) : The SenseFET and the control IC on a die in one package make it easy for the control IC to detect the abnormal over temperature of the SenseFET. If the temperature exceeds approximately 140 °C, the thermal shutdown triggers and the FPS stops operation. The FPS operates in auto-restart mode until the temperature decreases to around 80 °C, when normal operation resumes. 5. Soft-Start : The FPS has an internal soft-start circuit that increases the VS-PWM comparator inverting input voltage, together with the SenseFET current, slowly after it starts up. The typical soft-start time is 5ms. The pulse width to the power switching device is progressively increased to establish the correct working conditions for transformers, inductors, and capacitors. The voltage on the output capacitors is progressively increased with the intention of smoothly establishing the required output voltage. This helps prevent transformer saturation and reduces stress on the secondary diode during startup. 6. Burst-Mode Operation : To minimize power dissipation in standby mode, the FPS enters burst- mode operation. As the load decreases, the feedback voltage decreases. As shown in Figure 18, the device automatically enters burst mode when the feedback voltage drops below VBURL (750mV). At this point, switching stops and the output voltages start to drop at a rate dependent on standby current load. This causes the feedback voltage to rise. Once it passes VBURH (850mV), switching resumes. The feedback voltage then falls and the process repeats. Burst mode alternately enables and disables switching of the SenseFET, reducing switching loss in standby mode. |
Similar Part No. - FSQ510M |
|
Similar Description - FSQ510M |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
