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SS8014G 数据表(PDF) 4 Page - Silicon Standard Corp. |
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SS8014G 数据表(HTML) 4 Page - Silicon Standard Corp. |
4 / 6 page www.SiliconStandard.com 4 of 6 1/12/2005 Rev.2.11 SS8014G Figure 2. Adjustable Output Using External Feedback Resistors Over Current Protection The SS8014 use a current mirror to monitor the output current. A small portion of the PMOS output transis- tor’s current is mirrored onto a resistor such that the voltage across this resistor is proportional to the output current. This voltage is compared against the reference voltage. Once the output current exceeds the limit, the PMOS output transistor enters constant current mode. The current is set to 370mA typically. Over Temperature Protection To prevent excessive temperatures from occurring, the SS8014 has a built-in temperature monitoring circuit. When it detects the temperature is above 150 oC, the output transistor is turned off. When the temperature drops to below 135 oC, the output is turned on again. In this way, the SS8014 is protected against excessive junction temperatures during operation. Shutdown Mode When the SHDN pin is connected to a logic-low voltage, the SS8014 enters shutdown mode. All the analog cir- cuits are turned off completely, which reduces the cur- rent consumption to only the leakage current. The output is disconnected from the input. When the output has no load at all, the output voltage will be discharged to ground through the internal resistor voltage divider. Operating Region and Power Dissipation Since the SS8014 is a linear regulator, its power dissipa- tion is always given by P = IOUT (VIN – VOUT). The maximum power dissipation is given by: PD(MAX) = (TJ–TA)/ Θ JA,=150 oC-25oC/220oC/W= 568mW Where (TJ–TA) is the temperature difference the SS8014 die and the ambient air, Θ JA, is the thermal resistance of the chosen package to the ambient air. In the case of a SOT23-5 package, the thermal resistance is typi- cally 220 oC/Watt. The die attachment area of the SS8014’s lead frame is connected to pin 2, which is the GND pin. Therefore, the GND pin of SS8014 can carry away the heat of the SS8014 die very effectively. To improve the power dissi- pation, connect the GND pin to ground using a large ground plane near the GND pin. Capacitor Selection and Regulator Stability Normally, use a 1µF capacitor on the input and a 1µF capacitor on the output of the SS8014. Larger input ca- pacitor values and lower ESR provide better sup- ply-noise rejection and transient response. A higher- value input capacitor (10µF) may be necessary if large, fast transients are anticipated and the device is located several inches from the power source. Power-Supply Rejection and Operation from Sources Other than Batteries The SS8014 is designed to deliver low dropout voltages and low quiescent currents in battery powered sys- tems. Power-supply rejection is 42dB at low frequen- cies. When operating from sources other than batteries, im- prove supply-noise rejection and transient response by increasing the values of the input and output capacitors, and using passive filtering techniques. Load Transient Considerations The SS8014 load-transient response graphs show two components of the output response: a DC shift of the output voltage due to the different load currents, and the transient response. Typical overshoot for step changes in the load current from 0mA to 100mA is 12mV. Increasing the output capacitor's value and de- creasing its ESR attenuates transient spikes. Input-Output (Dropout) Voltage A regulator's minimum input-output voltage differential (or dropout voltage) determines the lowest usable sup- ply voltage. In battery-powered systems, this will de- termine the useful end-of-life battery voltage. Because the SS8014 use a P-channel MOSFET pass transistor, the dropout voltage is a function of R DS(ON) multiplied by the load current. IN OUT SHDN ADJ GND + - BATTERYCIN 1µF R1 R2 C OUT 1µF OUTPUT VOLTAGE 470pF R L IN OUT SHDN ADJ GND SS8014 + - BATTERYCIN 1µF R1 R2 C OUT 1µF OUTPUT VOLTAGE 470pF R L |
类似零件编号 - SS8014G |
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类似说明 - SS8014G |
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