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## NCV47711 Datasheet(PDF) 10 Page - ON Semiconductor

 No. de Pieza. NCV47711 Descripción 5 V to 20 V Adjustable LDO with Adjustable Current Limit and 3.3 V Logic Compatible Enable Input Descarga 11 Pages Scroll/Zoom 100% Fabricante ONSEMI [ON Semiconductor] Página de inicio http://www.onsemi.com Logo

## NCV47711 Datasheet(HTML) 10 Page - ON Semiconductor

 10 / 11 page NCV47711http://onsemi.com10The output voltage is calculated from the following formula.Ignoring the bias current into the ADJ pin:Vout + VREF1 1 )R1R2(eq. 2)Use R2 < 50 kW to avoid significant voltage output errorsdue to ADJ bias current.Designers should consider the tolerance of R1 and R2 duringthe design phase.Setting the Output Current LimitThe output current limit can be set between 10 mA and350 mA by external resistor RCSO (see Figure 1). CapacitorCCSO of 1 mF in parallel with RCSO is required for stabilityof current limit control circuitry (see Figure 1).VCSO + Iout RCSO1100(eq. 3)ILIM +10012.55RCSO(eq. 4)RCSO +10012.55ILIM(eq. 5)WhereRCSO− current limit setting resistorVCSO− voltage at CSO pin proportional to IoutILIM− current limit valueIout− output current actual valueCSO pin provides information about output current actualvalue. The CSO voltage is proportional to output currentaccording to Equation 3.Once output current reaches its limit value (ILIM) set byexternal resistor RCSO than voltage at CSO pin is typically2.55 V. Calculations of ILIM or RCSO values can be doneusing equations Equation 4 and Equation 5, respectively.Thermal ConsiderationsAs power in the NCV47711 increases, it might becomenecessary to provide some thermal relief. The maximumpower dissipation supported by the device is dependentupon board design and layout. Mounting pad configurationon the PCB, the board material, and the ambient temperatureaffect the rate of junction temperature rise for the part. Whenthe NCV47711 has good thermal conductivity through thePCB, the junction temperature will be relatively low withhigh power applications. The maximum dissipation theNCV47711 can handle is given by:PD(MAX) +TJ(MAX) * TARqJA(eq. 6)Since TJ is not recommended to exceed 150°C, then theNCV47711 soldered on 645 mm2, 1 oz copper area, FR4 candissipate up to 1.8 W and up to 4.3 W for 4 layers PCB (alllayers are 1 oz) when the ambient temperature (TA) is 25°C.See Figure 18 for RthJA versus PCB area. The powerdissipated by the NCV47711 can be calculated from thefollowing equations:PD + Vin Iq@Iout ) Iout Vin * Vout(eq. 7)orVin(MAX) [PD(MAX) ) Vout IoutIout ) Iq(eq. 8)HintsVin and GND printed circuit board traces should be aswide as possible. When the impedance of these traces ishigh, there is a chance to pick up noise or cause the regulatorto malfunction. Place external components, especially theoutput capacitor, as close as possible to the NCV47711 andmake traces as short as possible.Figure 18. Thermal Resistance vs. PCB Copper Area4060801001201401601800100200300400500600700COPPER HEAT SPREADER AREA (mm2)4 LAYERS PCB − all layers 1 oz CuSINGLE LAYER PCB 1 oz Cu020200220SINGLE LAYER PCB 2 oz CuORDERING INFORMATIONDeviceOutput VoltageMarkingPackageShipping†NCV47711PDAJR2GAdjustable47711SOIC−8 EP(Pb−Free)2500 / Tape & Reel†For information on tape and reel specifications,including part orientation and tape sizes, please refer to our Tape and Reel PackagingSpecifications Brochure, BRD8011/D.