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ISL9307IRTAANGZ-T7A Datasheet(PDF) 8 Page - Renesas Technology Corp |
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ISL9307IRTAANGZ-T7A Datasheet(HTML) 8 Page - Renesas Technology Corp |
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8 / 13 page  ISL9307 FN7931 Rev 3.00 Page 8 of 13 September 20, 2012 Soft-Start Soft-start reduces the in-rush current during the start-up stage. The soft-start block limits the current rising speed so that the output voltage rises in a controlled fashion. Overcurrent Protection The ISL9307 provides overcurrent protection for DCD1 and DCD2 for when an overload condition occurs. When the current at P-channel MOSFET is sensed to reach the current limit, the internal protection circuit is triggered to turn off the P-channel MOSFET immediately. DCD Short-Circuit Protection The ISL9307 provides short-circuit protection for both DCD1 and DCD2. The feedback voltage is monitored for output short-circuit protection. When the output voltage is sensed to be lower than a certain threshold, the internal circuit will change the PWM oscillator frequency to a lower frequenciy to protect the IC from damage. The P-channel MOSFET peak current limit remains active during this state. Undervoltage Lockout (UVLO) An undervoltage lockout (UVLO) circuit is provided on ISL9307. The UVLO circuit block can prevent abnormal operation in the event that the supply voltage is too low to guarantee proper operation. The UVLO on VINDCD1 is set for a typical 2.2V with 100mV hysteresis. VINLDO is set for a typical 1.4V with 50mV hysteresis. When the input voltage is sensed to be lower than the UVLO threshold, the related channel is disabled. Low Dropout Operation Both DCD1 and DCD2 converters feature low dropout operation to maximize battery life. When the input voltage drops to a level at which the converter can no longer operate under switching regulation to maintain the output voltage, the P-channel MOSFET is completely turned on (100% duty cycle). The dropout voltage under such a condition is the product of the load current and the ON-resistance of the P-channel MOSFET. Minimum required input voltage (VIN) under such a condition is the sum of output voltage plus voltage drop across the inductor and the P-channel MOSFET switch. Active Output Voltage Discharge For DCD1, DCD2 The ISL9307 offers a feature to actively discharge the output voltage of DCD1 and DCD2 via an internal bleeding resistor (typical 115Ω) when the channel is disabled. Thermal Shutdown The ISL9307 provides a built-in thermal protection function with thermal shutdown threshold temperature set at +155°C with +25°C hysteresis (typical). When the die temperature is sensed to reach +155°C, the regulator is completely shut down, and as the temperature is sensed to drop to +130°C (typical), the device resumes normal operation, starting from soft-start. Board Layout Recommendations The ISL9307 is a high frequency switching charger and hence the PCB layout is a very important design practice to ensure a satisfactory performance. The power loop is composed of the output inductor, L; the output capacitor, COUT; the SW pin; and the PGND pin. It is important to make the power loop as small as possible, and the connecting traces among them should be direct, short and wide. The same practice should be applied to the connection of the VIN pin; the input capacitor, CIN; and PGND. The switching node of the converter, the SW pin, and the traces connected to this node are very noisy, so keep the voltage feedback trace and other noise-sensitive traces away from these noisy traces. The input capacitor should be placed as close as possible to the VIN pin. The ground of the input and output capacitors should be connected as close as possible as well. In addition, a solid ground plane is helpful for good EMI performance. The ISL9307 employs a thermally enhanced TQFN package with an exposed pad. The exposed pad should be properly soldered onto the thermal pad of the board to remove heat from the IC. The thermal pad should be big enough for nine vias, as shown in Figure 4. FIGURE 4. EXPOSED THERMAL PAD |
Similar Part No. - ISL9307IRTAANGZ-T7A |
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Similar Description - ISL9307IRTAANGZ-T7A |
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