Outputvoltage

Vout (PWM)

Vout +1%

PFMComparator

threshold

VoltagePositioning

Lightload

PFMMode

moderatetoheavyload

PWMMode

TLV62065

SLVSAC4 – NOVEMBER 2010

www.ti.com

Figure 22. Power Save Mode Operation with automatic Mode transition

100% Duty Cycle Low Dropout Operation

The device starts to enter 100% duty cycle mode as the input voltage comes close to the nominal output voltage.

In order to maintain the output voltage, the High-Side MOSFET switch is turned on 100% for one or more cycles.

With further decreasing VIN the High-Side MOSFET switch is turned on completely. In this case the converter

offers a low input-to-output voltage difference. This is particularly useful in battery-powered applications to

achieve longest operation time by taking full advantage of the whole battery voltage range.

The minimum input voltage to maintain regulation depends on the load current and output voltage, and can be

calculated as:

With:

Undervoltage Lockout

The under voltage lockout circuit prevents the device from malfunctioning at low input voltages and from

excessive discharge of the battery. It disables the output stage of the converter once the falling VIN trips the

typically 1.95V.

Output Capacitor Discharge

With EN = GND, the device enters shutdown mode and all internal circuits are disabled. The SW pin is

connected to PGND via an internal resistor to discharge the output capacitor. This feature ensures a startup in a

discharged output capacitor once the converter is enabled again and prevents "floating" charge on the output

capacitor. The output voltage ramps up monotonic starting from 0V.

MODE SELECTION

The MODE pin allows mode selection between forced PWM mode and Power Save Mode.

14

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