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TLV73318PQDRVRQ1 データシート(PDF) 11 Page - Texas Instruments |
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TLV73318PQDRVRQ1 データシート(HTML) 11 Page - Texas Instruments |
11 / 27 page t = 120·R L 120+R L ·C OUT 11 TLV733P-Q1 www.ti.com SBVS283A – AUGUST 2016 – REVISED AUGUST 2016 Product Folder Links: TLV733P-Q1 Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated 7.3 Feature Description 7.3.1 Undervoltage Lockout (UVLO) The TLV733P-Q1 family uses an undervoltage lockout (UVLO) circuit that disables the output until the input voltage is greater than the rising UVLO voltage. This circuit ensures that the device does not exhibit any unpredictable behavior when the supply voltage is lower than the operational range of the internal circuitry. During UVLO disable, the output is connected to ground with a 120-Ω pulldown resistor. 7.3.2 Shutdown The enable pin (EN) is active high. Enable the device by forcing the EN pin to exceed VEN(HI) (0.9 V, minimum). Turn off the device by forcing the EN pin to drop below 0.35 V. If shutdown capability is not required, connect EN to IN. The TLV733P-Q1 has an internal pulldown MOSFET that connects a 120-Ω resistor to ground when the device is disabled. The discharge time after disabling depends on the output capacitance (COUT) and the load resistance (RL) in parallel with the 120-Ω pulldown resistor. The time constant is calculated in Equation 1: (1) 7.3.3 Internal Foldback Current Limit The TLV733P-Q1 has an internal foldback current limit that protects the regulator during fault conditions. The current allowed through the device is reduced when the output voltage falls. When the output is shorted, the LDO supplies a typical current of 150 mA. The output voltage is not regulated when the device is in current limit. In this condition, the output voltage is the product of the regulated current and the load resistance. When the device output is shorted, the PMOS pass transistor dissipates power [(VIN – VOUT) × IOS] until thermal shutdown is triggered and the device turns off. After the device cools down, the internal thermal shutdown circuit turns the device back on. If the fault condition continues, the device cycles between current limit and thermal shutdown; see the Thermal Information table for more details. The foldback current-limit circuit limits the current allowed through the device to current levels lower than the minimum current limit at a nominal VOUT current limit (ILIM) during startup. See Figure 6 to Figure 8 for typical foldback current limit values. If the output is loaded by a constant-current load during startup, or if the output voltage is negative when the device is enabled, then the load current demanded by the load can exceed the foldback current limit and the device may not rise to the full output voltage. For constant-current loads, disable the output load until the TLV733P-Q1 has fully risen to the nominal output voltage. The TLV733P-Q1 PMOS pass element has an intrinsic body diode that conducts current when the voltage at the OUT pin exceeds the voltage at the IN pin. Do not force the output voltage to exceed the input voltage because excessively high current can flow through the body diode. 7.3.4 Thermal Shutdown Thermal shutdown protection disables the output when the junction temperature rises to approximately 160°C. Disabling the device eliminates the power dissipated by the device, allowing the device to cool. When the junction temperature cools to approximately 140°C, the output circuitry is again enabled. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal protection circuit can cycle on and off. This cycling limits regulator dissipation, protecting the device from damage as a result of overheating. Activating the thermal shutdown feature usually indicates excessive power dissipation as a result of the product of the (VIN – VOUT) voltage and the load current. For reliable operation, limit junction temperature to 135°C (maximum). To estimate the margin of safety in a complete design, increase the ambient temperature until the thermal protection is triggered; use worst-case loads and signal conditions. The TLV733P-Q1 internal protection circuitry protects against overload conditions but is not intended to be activated in normal operation. Continuously running the TLV733P-Q1 into thermal shutdown degrades device reliability. |
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同様の説明 - TLV73318PQDRVRQ1 |
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