Electronic Components Datasheet Search |
|
FSDM0265RN Datasheet(PDF) 11 Page - Fairchild Semiconductor |
|
FSDM0265RN Datasheet(HTML) 11 Page - Fairchild Semiconductor |
11 / 20 page FSDL0165RN 11 Figure 6. Over load protection 4.2 Thermal Shutdown (TSD) : The Sense FET and the con- trol IC are integrated, making it easier for the control IC to detect the temperature of the Sense FET. When the tempera- ture exceeds approximately 140 °C, thermal shutdown is acti- vated. 4.3 Abnormal Over Current Protection (AOCP) : Figure 7. AOCP Function & Block Even though the FPSTM has OLP (Over Load Protection) and current mode PWM feedback, these are not enough to protect the FPSTM when a secondary side diode short or a transformer pin short occurs. In addition to start-up, soft- start is also activated at each restart attempt during auto- restart and when restarting after latch mode is activated. The FPSTM has an internal AOCP (Abnormal Over Current Pro- tection) circuit as shown in figure 7. When the gate turn-on signal is applied to the power Sense FET, the AOCP block is enabled and monitors the current through the sensing resis- tor. The voltage across the resistor is then compared with a preset AOCP level. If the sensing resistor voltage is greater than the AOCP level, pulse by pulse AOCP is triggered regardless of uncontrollable LEB time. Here, pulse by pulse AOCP stops Sense FET within 350nS after it is activated. 4.4 Over Voltage Protection (OVP) : In case of malfunc- tion in the secondary side feedback circuit, or feedback loop open caused by a defect of solder, the current through the opto-coupler transistor becomes almost zero. Then, Vfb climbs up in a similar manner to the over load situation, forc- ing the preset maximum current to be supplied to the SMPS until the over load protection is activated. Because excess energy is provided to the output, the output voltage may exceed the rated voltage before the over load protection is activated, resulting in the breakdown of the devices in the secondary side. In order to prevent this situation, an over voltage protection (OVP) circuit is employed. In general, Vcc is proportional to the output voltage and the FPSTM uses Vcc instead of directly monitoring the output voltage. If VCC exceeds 19V, OVP circuit is activated resulting in ter- mination of the switching operation. In order to avoid undes- ired activation of OVP during normal operation, Vcc should be properly designed to be below 19V. 5. Soft Start : The FPSTM has an internal soft start circuit that increases the feedback voltage together with the Sense FET current slowly after it starts up. The typical soft start time is 15msec, as shown in figure 8, where progressive increments of Sense FET current are allowed during the start-up phase. The pulse width to the power switching device is progres- sively 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 volt- age. It also helps to prevent transformer saturation and reduce the stress on the secondary diode. 1 t 2 t 3 t 4 t t 3V 6V Vcc 8V Delay current (5uA) charges the Cfb Delay current (5uA) charges the Cfb Delay current (5uA) charges the Cfb Delay current (5uA) charges the Cfb FPS switching FPS switching FPS switching FPS switching OLP Following Vcc Following Vcc Following Vcc Following Vcc 2 . _ , 8 . 2 , 3 ) 1 ( ); ) 1 ( 1 ( 1 1 fig fb fb fb C C K R V t V R t V In RC t = Ω = = − − = V t V t t V uA I I t V t t V C t delay delay fb 3 ) 1 ( ) 2 1 ( , 5 ; )) 1 ( ) 2 1 ( ( 2 = − + = − + = R SQ Vsense Vfb Out Driver Rsense CLK Drain V AOCP PWM COMPARATOR AOCP COMPARATOR LEB 1mS 15steps Current limit 0.98A 2.15A t Drain current [A] |
Similar Part No. - FSDM0265RN |
|
Similar Description - FSDM0265RN |
|
|
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 |