Electronic Components Datasheet Search |
|
ISL9211A Datasheet(PDF) 8 Page - Intersil Corporation |
|
ISL9211A Datasheet(HTML) 8 Page - Intersil Corporation |
8 / 12 page ISL9211A 8 FN6702.1 August 25, 2010 Theory of Operation The ISL9211A is an integrated circuit (IC) optimized to provide a redundant safety protection to a Li-ion battery from charging system failures. The IC monitors the input voltage, the battery voltage, and the charge current. When any of the above three parameters exceeds its limit, the IC turns off an internal N-channel MOSFET to remove the power from the charging system. In addition to the above protected parameters, the IC also monitors its own internal temperature and turns off the N-channel MOSFET when the temperature exceeds +150°C. Together with the battery charger IC and the protection module in a battery pack, the charging system has triple-level protection from overcharging the Li-ion battery and is two-fault tolerant. The ISL9211A protects up to 26V input voltage. Power-Up The ISL9211A has a power-on reset (POR) threshold of 2.47V (max). Before the input voltage reaches the POR threshold, the internal power NFET is off. Approximately 10ms after the input voltage exceeds the POR threshold, the IC resets itself and begins the soft-start. The 10ms delay allows any transients at the input during a hot insertion of the power supply to settle down before the IC starts to operate. The soft-start slowly turns on the power NFET to reduce the inrush current as well as the input voltage drop during the transition. The power-up sequence is illustrated in Figure 1. Input Overvoltage Protection (OVP) The input voltage is monitored by the comparator CP1 in the “Block Diagram” on page 2. CP1 has an accurate reference of 1.2V from the bandgap reference. The OVP threshold is set by the resistive divider consisting of R1 and R2. When the input voltage exceeds the threshold, the CP1 outputs a logic signal to turn off the power NFET within 1µs (see Figure 2) to prevent the high input voltage from damaging the electronics in the handheld system. The hysteresis for the input OVP threshold is given in the “Electrical Specifications” table on page 4. When the input overvoltage condition is removed, the ISL9211A re-enables the output by running through the soft-start, as shown in Figure 4. Because of the 10ms second delay before the soft-start, the output is never enabled if the input rises above the OVP threshold quickly, as shown in Figure 5. Battery Overvoltage Protection The battery voltage OVP is realized with the VB pin. The comparator CP3, as shown in the “Block Diagram” on page 2, monitors the VB pin and issues an overvoltage signal when the battery voltage exceeds the 4.34V battery OVP threshold. The threshold has 30mV built-in hysteresis. The comparator CP3 has a built-in 180µs blanking time to prevent any transient voltage from triggering the OVP. If the OVP situation still exists after the blanking time, the power NFET is turned off. The control logic contains a 4-bit binary counter that if the battery overvoltage event occurs 16 times, the power NFET is turned off permanently, as shown in Figure 6. Recycling the input power will reset the counter and restart the ISL9211A. The resistor between the VB pin and the battery, RVB, as shown in the “Typical Application Circuit” on page 1, is an important component. This resistor provides a current limit in case the VB pin is shorted to the input voltage under a failure mode. The VB pin leakage current under normal operation is negligible to allow a resistance of 200kΩ to 1MΩ be used. Overcurrent Protection (OCP) The current in the power NFET is limited to prevent charging the battery with an excessive current. The current is sensed using the voltage drop across the power FET after the it is turned on. The reference of the OCP is generated using a sensing FET Q2 (Mirror to Q1), as shown in the “Block Diagram” on page 2. The current FIGURE 13. ON-RESISTANCE vs TEMPERATURE AT DIFFERENT INPUT VOLTAGES Typical Operating Performance The test conditions for the Typical Operating Performance are: VIN = 5V, TA = +25°C, RILIM = 24.9kΩ, RVB = 200kΩ, Unless Otherwise Noted. (Continued) 0 50 100 150 200 250 300 350 -50 -30 -10 10 30 50 70 90 110 130 TEMPERATURE (°C) 4.3V 5.0V 3.0V |
Similar Part No. - ISL9211A |
|
Similar Description - ISL9211A |
|
|
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 |