Outputvoltage

Vout (PWM)

Vout +1%

PFMComparator

threshold

VoltagePositioning

Lightload

PFMMode

moderatetoheavyload

PWMMode

TPS62590

SLVS897C – JANUARY 2009 – REVISED DECEMBER 2015

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7.3 Feature Description

7.3.1 Dynamic Voltage Positioning

This feature reduces the voltage undershoots and overshoots at load steps from light to heavy load and vice

versa. It is active in power-save mode and regulates the output voltage 1% higher than the nominal value. This

provides more headroom for both the voltage drop at a load step, and the voltage increase at a load throw-off.

Figure 5. Power-Save Mode Operation

7.3.2 Undervoltage Lockout

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

excessive discharge of the battery and disables the output stage of the converter. The undervoltage lockout

7.3.3 Mode Selection

The MODE pin allows mode selection between forced PWM mode and power-save mode.

Connecting this pin to GND enables the power-save mode with automatic transition between PWM and PFM

mode. Pulling the MODE pin high forces the converter to operate in fixed frequency PWM mode even at light

load currents. This allows simple filtering of the switching frequency for noise-sensitive applications. In this mode,

the efficiency is lower compared to the power-save mode during light loads.

The condition of the MODE pin can be changed during operation and allows efficient power management by

adjusting the operation mode of the converter to the specific system requirements.

7.3.4 Enable

Afterwards, the device activates the soft-start circuit. The EN input can be used to control power sequencing in a

system with various DC–DC converters. The EN pin can be connected to the output of another converter, to

drive the EN pin high and getting a sequencing of supply rails. With EN = GND, the device enters shutdown

mode. In this mode, all circuits are disabled. In fixed output voltage versions, the internal resistor divider network

is disconnected from FB pin.

7.3.5 Thermal Shutdown

mode, the high-side and low-side MOSFETs are turned off. The device continues its operation when the junction

temperature falls below the thermal shutdown hysteresis.

8

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