Like any low-dropout regulator， the external capacitorsused with the RT9193 must be carefully selected forregulator stability and_performance. Using a capacitorwhose value is > 1μF on the RT9193 input and_the amountof capacitance can be increased without limit. The inputcapacitor must be located a distance of not more than0.5 inch from the input pin of the IC and_returned to aclean analog ground. Any good quality ceramic ortantalum can be used for this capacitor. The capacitorwith larger value and_lower ESR (equivalent seriesresistance) provides better PSRR and_line-transientresponse. The output capacitor must meet bothrequirements for minimum amount of capacitance andESR in all LDOs application. The RT9193 is designedspecifically to work with low ESR ceramic output capacitorin space-saving and_performance consideration. Usinga ceramic capacitor whose value is at least 1μF with ESRis > 25mΩ on the RT9193 output ensures stability. TheRT9193 still works well with output capacitor of othertypes due to the wide stable ESR range. Figure 1 showsthe curves of allowable ESR range as a function of loadcurrent for various output capacitor values. Outputcapacitor of larger capacitance can reduce noise andimprove load transient response， stability， and_PSRR. Theoutput capacitor should be located not more than 0.5inch from the VOUT pin of the RT9193 and_returned to aclean analog ground.Figure 1Bypass Capacitor and_Low NoiseConnecting a 22nF between the BP pin and_GND pinsignificantly reduces noise on the regulator output， it iscritical that the capacitor connection between the BP pinand_GND pin be direct and_PCB traces should be as shortas possible. There is a relationship between the bypasscapacitor value and_the LDO regulator turn on time. DCleakage on this pin can affect the LDO regulator outputnoise and_voltage regulation performance.Enable FunctionThe RT9193 features an LDO regulator enable/disablefunction. To assure the LDO regulator will switch on， theEN turn on control level must be greater than 1.2 volts.The LDO regulator will go into the shutdown mode whenthe voltage on the EN pin falls below 0.4 volts. For toprotecting the system， the RT9193 have a quick-dischargefunction. If the enable function is not needed in a specificapplication， it may be tied to VIN to keep the LDO regulatorin a continuously on state.Thermal ConsiderationsThermal protection limits power dissipation in RT9193.When the operation junction temperature exceeds 165°C，the OTP circuit starts the thermal shutdown function turnthe pass element off. The pass element turn on againafter the junction temperature cools by 30°C.For continue operation， do not exceed absolute maximumoperation junction temperature 125°C. The powerdissipation definition in device is :PD = (VIN?VOUT) x IOUT + VIN x IQThe maximum power dissipation depends on the thermalresistance of IC package， PCB layout， the rate ofsurroundings airflow and_temperature difference betweenjunction to ambient. The maximum power dissipation canbe calculated by following formula :PD(MAX) = ( TJ(MAX)? TA ) /θJAWhere TJ(MAX) is the maximum operation junctiontemperature 125°C， TA is the ambient temperature andtheθJA is the junction to ambient thermal resistanc