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RT9198-20PB Datasheet(PDF) 8 Page - Richtek Technology Corporation |
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RT9198-20PB Datasheet(HTML) 8 Page - Richtek Technology Corporation |
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8 / 12 page  RT9198T 8 DS9198T-04 April 2011 www.richtek.com Applications Information Like any low-dropout regulator, the external capacitors used with the RT9198T must be carefully selected for regulator stability and performance. Using a capacitor whose value is > 1 μF on the RT9198T input and the amount of capacitance can be increased without limit. The input capacitor must be located a distance of not more than 0.5 inch from the input pin of the IC and returned to a clean analog ground. Any good quality ceramic or tantalum can be used for this capacitor. The capacitor with larger value and lower ESR (equivalent series resistance) provides better PSRR and line-transient response. The output capacitor must meet both requirements for minimum amount of capacitance and ESR in all LDOs application. The RT9198T is designed specifically to work with low ESR ceramic output capacitor in space-saving and performance consideration. Using a ceramic capacitor whose value is at least 1 μF with ESR is > 20mΩ on the RT9198T output ensures stability. The RT9198T still works well with output capacitor of other types due to the wide stable ESR range. Figure 1. shows the curves of allowable ESR range as a function of load current for various output capacitor values. Output capacitor of larger capacitance can reduce noise and improve load transient response, stability, and PSRR. The output capacitor should be located not more than 0.5 inch from the VOUT pin of the RT9198T and returned to a clean analog ground. Thermal Considerations Thermal protection limits power dissipation in RT9198T. When the operation junction temperature exceeds 165 °C, the OTP circuit starts the thermal shutdown function and turns the pass element off. The pass element turn on again after the junction temperature cools by 30 °C. RT9198T lowers its OTP trip level from 165 °C to 110°C when output short circuit occurs (VOUT < 0.4V) as shown in Figure 2. This limits IC case temperature under 100 °C and provides maximum safety to end users when output short circuit occurs. Figure 1 Enable Function The RT9198T features an LDO regulator enable/disable function. To assure the LDO regulator will switch on, the EN turn on control level must be greater than 1.2 volts. The LDO regulator will go into the shutdown mode when the voltage on the EN pin falls below 0.4 volts. For to protecting the system, the RT9198T have a quick- discharge function. If the enable function is not needed in a specific application, it may be tied to VIN to keep the LDO regulator in a continuously on state. Figure 2. Short Circuit Thermal Folded Back Protection when Output Short Circuit Occurs V OUT Short to GND 0.4V V OUT I OUT TSD OTP Trip Point 165 C ° 110 C ° 110 C ° 80 C ° IC Temperature Region of Stable COUT ESR vs. Load Current 0.00 0.01 0.10 1.00 10.00 100.00 0 50 100 150 200 250 300 Load Current (mA) COUT = 1uF Instable Stable 100 10 1 RT9198T-15PU5 CIN = 1 μF, X7R Simulation Verify |
Similar Part No. - RT9198-20PB |
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