 |
поискавой системы для электроныых деталей |
|
|
поискавой системы для электроныых деталей |
|
SC21150ACSTRT датащи(PDF) 14 Page - Semtech Corporation |
|
|
|||||||||||||||||||||||||||||
SC21150ACSTRT датащи(HTML) 14 Page - Semtech Corporation |
|
|
14 / 20 page  SC21150 4 Synchronous Buck Converter The SC250 is a synchronous buck regulator that employs an adaptive on-time architecture to provide fast transient response and very small circuit area. The SC250 oper- ates over an input voltage range of 2.3 to 5.5V. Operating Modes The SC250 operates in one of four different modes depending on the status of VIN, VOUT, and load. PWM Adaptive On-time operation (AOT) PWM Minimum Off-time operation (Min Off) PFM (Pulse Frequency Modulation for Power Saving) Drop-Out operation (LDO mode) PWM AOT Mode Operation During PWM AOT operation the controller uses adaptive on-time control. The FB ripple signal is routed to a gain stage and then to the internal comparator and reference which trigger the high-side pulses. The reference includes a compensation ramp which emulates the inductor current to provide stable switching. AOT operation is used when the low-side pulse-width (off- time) is greater than the minimum 60nsec. A switching cycle in AOT mode is as follows: On-time: the cycle starts with the high-side mosfet turn-on. The pulse width is set by the following formula where f sw is 4MHz: Off-time: after the high-side on-time is com- pleted, the low-side mosfet turns on to begin the off-time. The off-time pulse width is set by the internal compensation ramp and under static conditions results in typically 4MHz switch- ing frequency. Note that the SC250 enters AOT operation if VIN is less than VOUT/0.88. Also note that connecting the FPWM to a logic high will disable the Power Save feature and lead to constant switching even under light load conditions. • • PWM Min Off Operation The device will enter Minimum Off-time operation (Min Off) when VIN, VOUT, and load conditions force the off- time (time between high-side pulses) to the minimum value, typically 60nsec. This indicates that the controller has reached maximum duty cycle for AOT operation and longer duty cycles are needed. In Min Off operation the SC250 uses constant off-time control. As in AOT operation, the FB ripple signal is routed to a gain stage and then to the internal AOT comparator and reference. In Min Off mode, the FB ripple triggers the low-side turn-on. Min Off switching cycle operation is as follows: Off-time: The low-side mosfet is on for a fixed Minimum Off time of 60nsec. This draws current from the output capacitor through the inductor via the LX pin and causes the output to fall. On-time: after the Min Off time of 60nsec has elapsed, the high-side mosfet turns on. This helps recharge the output capacitor and bring the output voltage up. The on-time pulse width is determined by the internal compensation ramp. Drop-out Operation When operating in Min Off mode, the off-time is constant and the high-side on-time varies in order to regulate the output. For cases where VIN is near VOUT, the high-side will remain on continually with 00% duty cycle. The output voltage will then be limited by the input voltage, high-side RDS ON and inductor DCR as shown in the fol- lowing equation: Note that RDS ON is a function of input voltage and tem- perature. Inductor DC resistance also increases with temperature. • • Applications Information |
|
|
ссылки URL |
| Вашему бизинису помогли Аллдатащит? [ DONATE ] |
Что такое Аллдатащит | реклама | контакт | Конфиденциальность | Ссылка на техническое описание | обмен ссыками | поиск по производителю 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 |
Russian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
