전자부품 데이터시트 검색엔진 |
|
CS5323-D 데이터시트(PDF) 11 Page - ON Semiconductor |
|
CS5323-D 데이터시트(HTML) 11 Page - ON Semiconductor |
11 / 16 page CS5323 http://onsemi.com 11 Ramp Size and Current Sensing Because the current ramp is used for both the PWM ramp and to sense current, the inductor and sense resistor values will be constrained. A small ramp will provide a quick transient response by minimizing the difference over which the COMP pin must travel between light and heavy loads, but a steady state ramp of 25 mVP–P or greater is typically required to prevent pulse skipping and minimize pulse width jitter. For resistive current sensing the combination of the inductor and sense resistor values must be chosen to provide a large enough steady state ramp. For large inductor values the sense resistor value must also be increased. For inductive current sensing the RC network must meet the requirement of L/RL = R × C to accurately sense the AC and DC components of the current the signal. Again the values for L and RL will be constrained in order to provide a large enough steady state ramp with a compensated current sense signal. A smaller L, or a larger RL than optimum might be required. But unlike resistive sensing, with inductive sensing small adjustments can be made easily with the values of R and C to increase the ramp size if needed. If RC is chosen to be smaller (faster) than L/RL, the AC portion of the current sensing signal will be scaled larger than the DC portion. This will provide a larger steady state ramp, but circuit performance will be affected and must be evaluated carefully. The current signal will overshoot during transients and settle at the rate determined by R × C. It will eventually settle to the correct DC level, but the error will decay with the time constant of R × C. If this error is excessive it will effect transient response, adaptive positioning and current limit. During transients the COMP pin will be required to overshoot along with the current signal in order to maintain the output voltage. The VDRP pin will also overshoot during transients and possibly slow the response. Single phase overcurrent will trip earlier than it would if compensated correctly and hiccup mode current limit will have a lower threshold for fast rise step loads than for slowly rising output currents. The waveforms in Figure 9 show a simulation of the current sense signal and the actual inductor current during a positive step in load current with values of L = 500 nH, RL = 1.6 mΩ, R1 = 20 k and C1 = .01 µF. For ideal current signal compensation the value of R1 should be 31 k Ω. Due to the faster than ideal RC time constant there is an overshoot of 50% and the overshoot decays with a 200 µs time constant. With this compensation the ILIM pin threshold must be set more than 50% above the full load current to avoid triggering hiccup mode during a large output load step. Figure 9. Inductive Sensing waveform during a Step with Fast RC Time Constant (50 ms/div) Current Limit Two levels of overcurrent protection are provided. Any time the voltage on a Current Sense pin exceeds CSREF by more than the Single Phase Pulse by Pulse Current Limit, the pwm comparator for that phase is turned off. This provides fast peak current protection for individual phases. The outputs of all the currents are also summed and filtered to compare an averaged current signal to the voltage on the ILIM pin. If this voltage is exceeded, the fault latch trips and the SS capacitor is discharged by a 5 µA source until the COMP pin reaches 0.2 V. Then soft–start begins. The converter will continue to operate in this mode until the fault condition is corrected. Overvoltage Protection Overvoltage protection (OVP) is provided as a result of the normal operation of the enhanced V2 control topology with synchronous rectifiers. The control loop responds to an overvoltage condition within 400 ns, causing the top MOSFET’s to shut off, and the synchronous MOSFET’s to turn on. This results in a “crowbar” action to clamp the output voltage and prevents damage to the load. The regulator will remain in this state until the overvoltage condition ceases or the input voltage is pulled low. Transient Response and Adaptive Positioning For applications with fast transient currents the output filter is frequently sized larger than ripple currents require in |
유사한 부품 번호 - CS5323-D |
|
유사한 설명 - CS5323-D |
|
|
링크 URL |
개인정보취급방침 |
ALLDATASHEET.CO.KR |
ALLDATASHEET 가 귀하에 도움이 되셨나요? [ DONATE ] |
Alldatasheet는? | 광고문의 | 운영자에게 연락하기 | 개인정보취급방침 | 링크교환 | 제조사별 검색 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 |