LMR16006Y-Q1

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SNVSAC1 – JUNE 2015

Feature Description (continued)

8.3.6 Overvoltage Transient Protection

The LMR16006Y-Q1 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.

8.3.7 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.

8.4 Device Functional Modes

8.4.1 Continuous Conduction Mode

The LMR16006Y-Q1 steps the input voltage down to a lower output voltage. In continuous conduction mode

(when the inductor current never reaches zero at CCM), the buck regulator operates in two cycles. The power

reverse biased. Energy is collected in the inductor and the load current is supplied by Cout and the rising current

through the inductor. During the second cycle the transistor is open and the diode is forward biased due to the

fact that the inductor current cannot instantaneously change direction. The energy stored in the inductor is

transferred to the load and output capacitor. The ratio of these two cycles determines the output voltage. The

D and D' will be required for design calculations.

8.4.2 ECO Mode

The LMR16006Y-Q1 operates in ECO mode at light load currents to improve efficiency by reducing switching

and gate drive losses. The LMR16006Y-Q1 is designed so that if the output voltage is within regulation and the

device enters ECO mode. For ECO mode operation, the LMR16006Y-Q1 senses peak current, not average or

inductor value. When the load current is low and the output voltage is within regulation, the device enters an

ECO mode and draws only 28 µA input quiescent current.

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