Electronic Components Datasheet Search |
|
SP6128AEY Datasheet(PDF) 5 Page - Sipex Corporation |
|
SP6128AEY Datasheet(HTML) 5 Page - Sipex Corporation |
5 / 10 page 5 Rev. 05/25/04 SP6128A Low Voltage, Synchronous Step Down PWM Controller © Copyright 2004 Sipex Corporation When the overcurrent threshold is exceeded, the overcurrent comparator sets the fault latch and terminates the output pulses. The controller stops switching and goes through a hiccup se- quence. This prevents excessive power dissipa- tion in the external power MOSFETs during an overload condition. An internal delay circuit prevents that very short and mild overload con- ditions, that could occur during a load transient, activate the current limit circuit. A low power sleep mode can be invoked in the SP6128A by externally forcing the COMP pin below 0.3V. Quiescent supply current in sleep mode is typically less than 30 µA. An internal 5 µA pull-up current at the COMP pin brings the SP6128A out of shutdown mode. An internal 0.8V 1.5% reference allows out- put voltage adjustment for low voltage appli- cations. The SP6128A also includes an accurate under- voltage lockout that shuts down the controller when the input voltage falls below 2.7V. Output overvoltage protection is achieved by turning off the high side switch and turning on the low side N-channel MOSFET 100% of the time. Enable Low quiescent mode or “Sleep Mode” is initi- ated by pulling the COMP pin below 0.3V with an external open-drain or open-collector tran- sistor. Supply current is reduced to 30 µA (typi- cal) in shutdown. On power-up, assuming that VCC has exceeded the UVLO start threshold (2.8V), an internal 5 µA pull-up current at the COMP pin brings the SP6128A out of shutdown mode and ensures start-up. During normal oper- ating conditions and in absence of a fault, an internal clamp prevents the COMP pin from swinging below 0.6V. This guarantees that dur- ing mild transient conditions, due either to line or load variations, the SP6128A does not enter shutdown unless it is externally activated. During Sleep Mode, the high side and low side MOSFETS are turned off and the internal soft start voltage is held low. UVLO Assuming that there is not shutdown condition present, then the voltage on the VCC pin deter- mines operation of the SP6128A. As VCC rises, the UVLO block monitors VCC and keeps the high side and low side MOSFETS off and the internal SS voltage low until VCC reaches 2.8V. If no faults are present, the SP6128A will ini- tiate a soft start when VCC exceeds 2.8 V. Hysteresis (about 100mV) in the UVLO com- parator provides noise immunity at start-up. Soft Start Soft start is required on step-down controllers to prevent excess inrush current through the power train during start-up. Typically this is managed by sourcing a controlled current into a timing capacitor and then using the voltage across this capacitor to slowly ramp up either the error amp reference or the error amp output (COMP). The control loop creates narrow width driver pulses while the output voltage is low and allows these pulses to increase to their steady-state duty cycle as the output voltage increases to its regu- lated value. As a result of controlling the induc- tor volt*second product during startup, inrush current is also controlled. In the SP6128A the duration of the soft-start is controlled by an internal timing circuit that provides a 0.3V/mS slew-rate, which is used during startup and overcurrent to set the hiccup time. The SP6128A implements soft-start by ramping up the error amplifier reference voltage providing a controlled slew-rate of the output voltage, thereby preventing overshoot and in- rush current at power up. The presence of the output capacitor creates extra currentdrawduringstartup. Simplystated,dVOUT/ dt requires an average sustained current in the output capacitor and this current must be consid- ered while calculating peak inrush current and over current thresholds. An approximate expres- sion to determine the excess inrush current due to the dVOUT/dt of the output capacitor COUT is: Iinrush = COUT x (0.27 V/ms) x VOUT 0.8V OPERATION: continued |
Similar Part No. - SP6128AEY |
|
Similar Description - SP6128AEY |
|
|
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 |