 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SC1404ITSTR Datasheet(PDF) 10 Page - Semtech Corporation |
|
||||||||||||||||||||||||||||||
SC1404ITSTR Datasheet(HTML) 10 Page - Semtech Corporation |
|
|
10 / 27 page  10 2003 Semtech Corp. www.semtech.com SC1404 PRELIMINARY POWER MANAGEMENT Functional Information Current Sense (CSH, CSL) The output current of the power supply is sensed as the voltage drop across an external resistor between the CSH and CSL pins. Overcurrent is detected when the current sense voltage exceeds +/- 50mV. A positive overcurrent will turn off the high-side driver, a negative overcurrent will turn off the low-side driver; each on a cycle-by-cycle basis. Oscillator When the SYNC pin is set high the oscillator runs at 300KHz; when SYNC is set low the frequency is 200KHz. The oscillator can also be synchronized to the falling edge of a clock on the SYNC pin with a frequency between 240KHz and 350KHz. In general, 200KHz operation is used for highest efficiency while 300KHz leads to less output ripple and/or smaller filter components. Fault Protection In addition to cycle-by-cycle current limit, the SC1404 monitors over-temperature, and output overvoltage and undervoltage conditions. The overtemperature detection will shut the part down if the die temperature exceeds 150 °C with 10°C of hysteresis. If either SMPS output is more than 10% above its nominal value, both SMPS are latched off and the low-side MOSFETS are latched on. To prevent the output from ringing too far below ground in a fault condition, a 1A Schottky diode should be placed across each output. Two different levels of undervoltage are detected. If the output falls 10% below its nominal output, the RESET# output is pulled low.If the output falls 25% below its nominal output following a start-up delay, both SMPS are latched off. Both of the latched fault modes persist until SHDN# or ON3 is toggled, or the V+ input is brought below 1V. Power up Controls and Soft Start The user has control of the SC1404 RESET# by setting the SEQ, ON3 and ON5 pins as described in the following table. At startup, the RESET# pin is held low for 32K switching cycles. Another timer is used to enable the undervoltage protection. The undervoltage protection circuitry is enabled after 6144 switching cycles, at which time the SMPS should be in regulation. When SEQ is set to REF, the RESET# only monitors the 3.3V SMPS and the 5V SMPS is ignored. Each SMPS contains its own counter and DAC to gradually increase the current limit at startup to prevent surge currents. The current limit is increased from 0, 20%, 40%, 60%, 80%, to 100% linearly over the course of 512 switching cycles. 12OUT Supply The 12OUT linear regulator is capable of supplying 200mA. The input voltage to the 12OUT regulator is generated by a secondary winding on the 5V SMPS inductor. A heavy load on the 12OUT regulator when the 5V SMPS is in PSAVE will cause the VDD input to drop, browning out the regulator. If the output drops 0.8% from its nominal value, the 5V SMPS is forced out of PSAVE mode and into continuous conduction mode for several cycles. This recharges the bulk input capacitor on the VDD. The 12OUT linear regulator also has a current limit to prevent damage under short circuit conditions. Over-voltage protection is provided on the VDD input. If the VDD input is above 19V, an over-voltage is detected and a 10mA current shunt load is applied to VDD. The over-voltage threshold has a 0.5V hysteresis. Shutdown and Operating Modes Holding the SHDN# pin low disables the SC1404, reducing the V+ input current to less than 10uA. When SHDN goes high, the part enters a standby mode where the VL regulator and VREF are enabled. Turning on either SMPS will put the SC1404 in run mode. # N D H S# N D H S # N D H S # N D H S# N D H S3 N O3 N O 3 N O 3 N O3 N O5 N O5 N O 5 N O 5 N O5 N OE D O ME D O M E D O M E D O ME D O MN O I T P I R C S E DN O I T P I R C S E D N O I T P I R C S E D N O I T P I R C S E DN O I T P I R C S E D w o LX X n w o d -t u h Ss a i b m u m i n i M t n e r r u c h g i Hw o Lw o Ly b d n a t SL V d n a F E R V r o t a l u g e r e l b a n e h g i Hh g i Hh g i Hn u R e d o M S P M S h t o B g n i n n u R g n i d a o L ( e c n a t s i s e R Ω) 1 1 5K 7 6 . 2K 9 . 9 4K 5 5 2g e M 1 m o r f n o it a i v e D V 0 2 9 4 . 2 = f e r V V m 3 . 8V m 1 . 3V m 5 . 0V m 3 . 0V m 0 The REF output is accurate to +/- 2% over temperature. It is ca- pable of delivering 5mA max and should be bypassed with 1uF minimum. Loading the REF pin will reduce the REF voltage slightly. |
Similar Part No. - SC1404ITSTR |
|
Similar Description - SC1404ITSTR |
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
