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NCV59749 Datenblatt(PDF) 8 Page - ON Semiconductor |
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NCV59749 Datenblatt(HTML) 8 Page - ON Semiconductor |
8 / 10 page NCV59749 www.onsemi.com 8 APPLICATIONS INFORMATION The NCV59749 dual−rail very low dropout voltage regulator is using NMOS pass transistor for output voltage regulation from VIN voltage. All the low current internal controll circuitry is powered from the VBIAS voltage. The use of an NMOS pass transistor offers several advantages in applications. Unlike a PMOS topology devices, the output capacitor has reduced impact on loop stability. Vin to Vout operating voltage difference can be very low compared with standard PMOS regulators in very low Vin applications. The NCV59749 offers programmable smooth monotonic start-up. The controlled voltage rising limits the inrush current what is advantageous in applications with large capacitive loads. The Voltage Controlled Soft Start timing is programmable by external Css capacitor value. The Enable (EN) input is equipped with internal hysteresis and deglitch filter. Open Drain type Power Good (PG) output is available for Vout monitoring and sequencing of other devices. NCV59749 is a Adjustable linear regulator. The required Output voltage can be adjusted by two external resistors. Typical application schematics is shown in Figure 16. Figure 16. Typical Application Schematics V OUT + 0.8 1 ) R 1 R2 NCV59749 Dropout Voltage Because of two power supply inputs VIN and VBIAS and one VOUT regulator output, there are two Dropout voltages specified. The first, the VIN Dropout voltage is the voltage difference (VIN – VOUT) when VOUT starts to decrease by percents specified in the Electrical Characteristics table. VBIAS is high enough, specific value is published in the Electrical Characteristics table. The second, VBIAS dropout voltage is the voltage difference (VBIAS – VOUT) when VIN and VBIAS pins are joined together and VOUT starts to decrease. Input and Output Capacitors The device is designed to be stable for all available types and values of output capacitors ≥ 2.2 mF. The device is also stable with multiple capacitors in parallel, which can be of any type or value. In applications where no low input supplies impedance available (PCB inductance in VIN and/or VBIAS inputs as example), the recommended CIN and CBIAS value is 1 mF or greater. Ceramic or other low ESR capacitors are recommended. For the best performance all the capacitors should be connected to the NCV59749 respective pins directly in the device PCB copper layer, not through vias having not negligible impedance. Enable Operation The enable pin will turn the regulator on or off. The threshold limits are covered in the electrical characteristics table in this data sheet. If the enable function is not to be used then the pin should be connected to VIN or VBIAS. Output Noise When the NCV59749 device reaches the end of the Soft−Start cycle, the Soft Start capacitor is switched to serve as a Noise filtering capacitor. Output Voltage Adjust The output voltage can be adjusted from 0.8 V to 3.6 V using resistors divider between the output and the FB input. Recommended resistor values for frequently used voltages can be found in the Table 6. Programmable Soft−Start The Soft-Start ramp time depends on the Soft Start charging current ISS, Soft-Start capacitor value CSS and internal reference voltage VREF. The Soft –Start time can be calculated using following equations: tss = CSS x (VREF / ISS) [s, F,V,A] or in more practical units tSS = CSS x 0.8V / 0.44 = CSS x 1.82 where tss = Soft−Start time in miliseconds CSS = Soft−Start capacitor value in nano Farads Capacitor values for frequently used Soft-Start times can be found in the Table 7. The maximal recommended value of CSS capacitor is 15 nF. For higher CSS values the capacitor full discharging before new Soft-Start cycle is not guaranteed. Current Limitation The internal Current Limitation circuitry allows the device to supply the full nominal current and surges but protects the device against Current Overload or Short. Thermal Protection Internal thermal shutdown (TSD) circuitry is provided to protect the integrated circuit in the event that the maximum junction temperature is exceeded. When TSD activated , the regulator output turns off. When cooling down under the low temperature threshold, device output is activated again. This TSD feature is provided to prevent failures from accidental overheating. |
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Ähnliche Beschreibung - NCV59749 |
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