Electronic Components Datasheet Search |
|
FSFR1900 Datasheet(PDF) 11 Page - Fairchild Semiconductor |
|
FSFR1900 Datasheet(HTML) 11 Page - Fairchild Semiconductor |
11 / 18 page © 2007 Fairchild Semiconductor Corporation www.fairchildsemi.com FSFR series Rev.1.0.9 11 in Figure 19. FSFR-series also has an internal soft-start for 3ms to reduce the current overshoot during the initial cycles, which adds 40kHz to the initial frequency of the external soft-start circuit, as shown in Figure 20. The initial frequency of the soft-start is given as: min 5.2 5.2 ( ) 100 40 ( ) ISS SS kk f kHz RR ΩΩ =+ × + (3) It is typical to set the initial frequency of soft-start two ~ three times the resonant frequency (fO) of the resonant network. The soft-start time is three to four times of the RC time constant. The RC time constant is as follows: SS SS SS TR C =⋅ (4) f s time Control loop take over 40kHz f ISS Figure 20. Frequency Sweeping of Soft-start 4. Control Pin: The FSFR-series has a control pin for protection, cycle skipping, and remote on/off. Figure 21 shows the internal block diagram for control pin. Figure 21. Internal Block of Control Pin Protection: When the control pin voltage exceeds 5V, protection is triggered. Detailed applications are described in the protection section. Pulse Skipping: FSFR-series stops switching when the control pin voltage drops below 0.4V and resumes switching when the control pin voltage rises above 0.6V. To use pulse-skipping, the control pin should be connected to the opto-coupler collector pin. The frequency that causes pulse skipping is given as: () kHz 100 x R k 16 . 4 R k 2 . 5 max min SKIP + = (5) Figure 22. Control Pin Configuration for Pulse Skipping Remote On / Off: When an auxiliary power supply is used for standby, the main power stage using FSFR- series can be shut down by pulling down the control pin voltage, as shown in Figure 23. R1 and C1 are used to ensure soft-start when switching resumes. OP1 R min FPS Main Output Main Off Aux Output R1 C1 OP1 R T CON Figure 23. Remote On / Off Circuit 4. Current Sensing Method Current Sensing Using Resistor: FSFR-series senses drain current as a negative voltage, as shown in Figure 24 and Figure 25. Half-wave sensing allows low power dissipation in the sensing resistor, while full-wave sensing has less switching noise in the sensing signal. |
Similar Part No. - FSFR1900 |
|
Similar Description - FSFR1900 |
|
|
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 |