Electronic Components Datasheet Search |
|
SC2612E Datasheet(PDF) 6 Page - Semtech Corporation |
|
SC2612E Datasheet(HTML) 6 Page - Semtech Corporation |
6 / 11 page 6 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC2612E COMPENSA COMPENSA COMPENSA COMPENSA COMPENSATION COMPONENTS TION COMPONENTS TION COMPONENTS TION COMPONENTS TION COMPONENTS - Once the filter com- ponents have been determined, the compensation com- ponents can be calculated. The goal of compensation is to modify the frequency response characteristics of the error amplifier to ensure that the closed loop feedback system has the highest gain and bandwidth possible while maintaining stability. A simplified stability criteria states that the open loop gain of the converter should fall through 0dB at 20dB/ decade at a frequency no higher than 20-25% of the switching frequency. This objective is most simply met by generating asymp- totic bode plots of the small signal response of the vari- ous sections of the converter. L VOUT Co SC2612E AND FETS FB OUT COMP Ra MODULATOR REF + - EA Rb Resr Zp Zf Zs It is convenient to split the converter into two sections, the Error amp and compensation components being one section and the Modulator, output filter and divider be- ing the other. First calculate the DC Filter+Modulator+Divider gain The DC filter gain is always 0dB, the Modulator gain is 19dB at 5V in and is proportional to Vin, so modulator gain at any input voltage is. ÷ ø ö ç è æ × + = 5 20 19 IN MOD V Log G the divider gain is given by ÷÷ø ö ççè æ + × = 8 5 8 20 R R R Log G DIV So the total Filter+Modulator+Divider DC Gain is ÷÷ø ö ççè æ + × + ÷ ø ö ç è æ × + = B A B IN FMD R R R Log V Log G 20 5 20 19 Calculate the filter double pole frequency (Fp(lc)) LCo ) lc ( Fp p = 2 1 and calculate ESR Zero frequency (Fz(esr)) sr Re Co ) esr ( Fz × × p = 2 1 Choose an open loop crossover frequency (Fco) no higher than 20% of the switching frequency (Fs). The proximity of Fz(esr) to the crossover frequency Fco determines the type of compensation required, if Fz(esr)>Fco/4, use type 3 compensation, otherwise use type 2. Type 1 compensation is not appropriate and is not discussed here. Type 2 Example As an example of type 2 compensation, we will use the Evaluation board schematic. 3.3uH VOUT 3000uF SC2612E AND FETS FB OUT COMP 6.98k MODULATOR REF + - EA 8.06k 22mOhm Cs Cp Rs Vin=5V The total Filter+Modulator+Divider DC Gain is dB . . . . Log Log G FMD 6 13 06 8 98 6 06 8 20 5 5 20 19 = ÷ ø ö ç è æ + × + ÷ ø ö ç è æ × + = This is drawn as the line A-B in Fig2 kHz . . LCo ) lc ( Fp 6 1 10 3000 10 3 3 2 1 2 1 6 6 » × × × p = p = - - This is point B in Fig2. kHz . ) esr ( Fz 4 2 10 22 10 3000 2 1 3 6 = × × × × p = - - This is point C in Fig2., the line joining B-C slopes at - 40dB/decade, the line joining C-D slopes at -20dB/de- cade. For 500kHz switching frequency, crossover is designed for 100kHz. Since Fz(esr)<<Fco/4 Type 2 compensation is appropri- ate. |
Similar Part No. - SC2612E |
|
Similar Description - SC2612E |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |