 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ISL8009AIRZ-T Datasheet(PDF) 11 Page - Intersil Corporation |
|
||||||||||||||||||||||||||||||
ISL8009AIRZ-T Datasheet(HTML) 11 Page - Intersil Corporation |
|
|
11 / 13 page  11 FN6656.2 November 19, 2009 Once the skip mode is entered, the pulse modulation starts being controlled by the SKIP comparator shown in Figure 25. Each pulse cycle is still synchronized by the PWM clock. The P-MOSFET is turned on at the clock and turned off when its current reaches 20% of the current limit value (0.2V at the CSA output). As the average inductor current in each cycle is higher than the average current of the load, the output voltage rises cycle over cycle. When the output voltage reaches 1.5% above the nominal voltage, the P-MOSFET is turned off immediately and the inductor current is fully discharged to zero and stays at zero. The output voltage reduces gradually due to the load current discharging the output capacitor. When the output voltage drops to the nominal voltage, the P-MOSFET will be turned on again at the clock, repeating the previous operations. The regulator resumes normal PWM mode operation when the output voltage drops 1.5% below the nominal voltage. Mode Control The ISL8009A has a SKIP pin that controls the operation mode. When the SKIP pin is driven to low or shorted to ground, the regulator operates in a forced PWM mode. The forced PWM mode remains the fixed PWM frequency at light load instead of entering the skip mode. Overcurrent Protection The overcurrent protection is realized by monitoring the CSA output with the OCP comparator, as shown in Figure 25. The current sensing circuit has a gain of 0.4V/A, from the N-MOSFET current to the CSA output. When the CSA output reaches 0.8V, (which is equivalent to 2A for the switch current) the OCP comparator is tripped to turn off the P-MOSFET immediately. Short-Circuit Protection A short-circuit protection SCP comparator monitors the VFB pin voltage for output short-circuit protection. When the VFB is lower than 0.2V, the SCP comparator forces the PWM oscillator frequency to drop to 1/3 of the normal operation value. This comparator is effective during start- up or an output short-circuit event. RSI/POR Function When powering up, the open-collector Power-On-Reset output holds low for about 1ms after VO reaches the preset voltage. When the active-HI reset signal RSI is issued, POR goes to low immediately and holds for the same period of time after RSI comes back to LOW. The output voltage is unaffected (Figure 28). When the function is not used, connect RSI to ground and leave the pull-up resistor, R1, open at the POR pin. The POR output also serves as a 1ms delayed Power- Good signal when the pull-up resistor, R1, is installed. The RSI pin needs to be directly or indirectly through another resistor connected to ground for this to function properly. . UVLO When the input voltage is below the undervoltage lock out (UVLO) threshold, the regulator is disabled. Soft-Start-Up The soft start-up eliminates the in-rush current during the start-up. The soft-start block outputs a ramp reference to both the voltage loop and the current loop. The two ramps limit the inductor current rising speed as well as the output voltage speed so that the output voltage rises in a controlled fashion. At the very beginning of the start-up, the output voltage is less than 0.2V; hence the PWM operating frequency is 1/3 of the normal frequency. Power MOSFETs The power MOSFETs are optimized for best efficiency. The ON-resistance for the P-MOSFET is typically 120mΩ and the ON-resistance for the N-MOSFET is typically 110mΩ. Duty Cycle The ISL8009A features duty cycle operation to maximize the battery life. When the battery voltage drops to a level that the ISL8009A can no longer maintain the regulation at the output, the regulator completely turns on the P- MOSFET. The maximum drop out voltage under the duty- cycle operation is the product of the load current and the ON-resistance of the P-MOSFET. Enable The Enable (EN) input allows the user to control the turning on or off of the regulator for purposes such as power-up sequencing. When the regulator is enabled, there is typically a 600µs delay for waking up the bandgap reference, then the soft-start-up begins. When the regulator is disabled, the P-MOSFET and the N- MOSFET are turned off immediately. The 100Ω soft discharge resistor from LX to GDN is activated and pulls the output to 0V. Thermal Shutdown The ISL8009A has built-in thermal protection. When the internal temperature reaches +140°C, the regulator is completely shutdown. As the temperature drops to +120°C, the ISL8009A resumes operation by stepping through a soft-start-up. 2ms MIN 25ns 2ms POR RSI VO FIGURE 28. RSI AND POR TIMING DIAGRAM ISL8009A |
Similar Part No. - ISL8009AIRZ-T |
|
Similar Description - ISL8009AIRZ-T |
|
|
|
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
