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LMR14006YDDCR Datasheet(PDF) 9 Page - Texas Instruments |
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LMR14006YDDCR Datasheet(HTML) 9 Page - Texas Instruments |
9 / 20 page LMR14003, LMR14006 www.ti.com SNVSA10 – NOVEMBER 2013 Enable (/SHDN) and VIN Under Voltage Lockout LMR14003/6 /SHDN pin is a high voltage tolerant input with an internal pull up circuit. The device can be enabled even if the /SHDN pin is floating. The regulator can also be turned on using 1.23V or higher logic signals. If the use of a higher voltage is desired due to system or other constraints, a 100k Ω or larger resistor is recommended between the applied voltage and the /SHDN pin to protect the device. When /SHDN is pulled down to 0V, the chip is turned off and enters the lowest shutdown current mode. In shutdown mode the supply current will be decreased to approximately 1µA. If the shutdown function is not to be used the /SHDN pin may be tied to VIN. The maximum voltage to the SHDN pin should not exceed 40V. LMR14003/6 has an internal UVLO circuit to shutdown the output if the input voltage falls below an internally fixed UVLO threshold level. This ensures that the regulator is not latched into an unknown state during low input voltage conditions. The regulator will power up when the input voltage exceeds the voltage level. If there is a requirement for a higher UVLO voltage, the /SHDN can be used to adjust the input voltage UVLO by using external resistors. Current Limit The LMR14003/6 implements current mode control which uses the internal COMP voltage to turn off the high side MOSFET on a cycle-by-cycle basis. Each cycle the switch current and internal COMP voltage are compared, when the peak switch current intersects the COMP voltage, the high side switch is turned off. During overcurrent conditions that pull the output voltage low, the error amplifier will respond by driving the COMP node high, increasing the switch current. The error amplifier output is clamped internally, which functions as a switch current limit. Overvoltage Transient Protection The LMR14003/6 incorporates an overvoltage transient protection (OVTP) circuit to minimize voltage overshoot when recovering from output fault conditions or strong unload transients on power supply designs with low value output capacitance. For example, when the power supply output is overloaded the error amplifier compares the actual output voltage to the internal reference voltage. If the FB pin voltage is lower than the internal reference voltage for a considerable time, the output of the error amplifier will respond by clamping the error amplifier output to a high voltage. Thus, requesting the maximum output current. Once the condition is removed, the regulator output rises and the error amplifier output transitions to the steady state duty cycle. In some applications, the power supply output voltage can respond faster than the error amplifier output can respond, this actuality leads to the possibility of an output overshoot. The OVTP feature minimizes the output overshoot, when using a low value output capacitor, by implementing a circuit to compare the FB pin voltage to OVTP threshold which is 108% of the internal voltage reference. If the FB pin voltage is greater than the OVTP threshold, the high side MOSFET is disabled preventing current from flowing to the output and minimizing output overshoot. When the FB voltage drops lower than the OVTP threshold, the high side MOSFET is allowed to turn on at the next clock cycle. Thermal Shutdown The device implements an internal thermal shutdown to protect itself if the junction temperature exceeds 170°C(typ). The thermal shutdown forces the device to stop switching when the junction temperature exceeds the thermal trip threshold. Once the junction temperature decreases below 160°C(typ), the device reinitiates the power up sequence. Copyright © 2013, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: LMR14003 LMR14006 |
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