TLV62065

SLVSAC4B – NOVEMBER 2010 – REVISED DECEMBER 2015

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7.3 Feature Description

7.3.1 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.

7.3.2 Enable

The device is enabled by setting EN pin to high. At first, the internal reference is activated and the internal

analog circuits are settled. Afterwards, the soft-start is activated and the output voltage is ramped up. The output

voltages reaches 95% of its nominal value within tSTART of typically 500 µs after the device has been enabled.

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 and the SW pin is

connected to PGND through an internal resistor to discharge the output.

7.3.3 Undervoltage Lockout

The undervoltage 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

undervoltage lockout threshold VUVLO. The undervoltage lockout threshold VUVLO for falling VIN is typically 1.78 V.

The device starts operation once the rising VIN trips the undervoltage lockout threshold VUVLO again at typically

1.95 V.

7.3.4 Thermal Shutdown

As soon as the junction temperature, TJ, exceeds 150°C (typical) the device goes into thermal shutdown. In this

mode, the high-side and low-side MOSFETs are turned off. The device continues its operation with a soft-start

once the junction temperature falls below the thermal shutdown hysteresis.

7.4 Device Functional Modes

7.4.1 Soft-Start

The TLV62065 has an internal soft-start circuit that controls the ramp up of the output voltage. Once the

converter is enabled and the input voltage is above the undervoltage lockout threshold VUVLO the output voltage

ramps up from 5% to 95% of its nominal value within tRamp of typically 250 µs.

This limits the inrush current in the converter during start-up and prevents possible input voltage drops when a

battery or high impedance power source is used.

During soft-start, the switch current limit is reduced to 1/3 of its nominal value ILIMF until the output voltage

reaches 1/3 of its nominal value. Once the output voltage trips this threshold, the device operates with its

nominal current limit ILIMF.

7.4.2 Power-Save Mode

At TLV62065 pulling the MODE pin low enables power-save mode. If the load current decreases, the converter

enters power-save mode operation automatically. During power save mode the converter skips switching and

operates with reduced frequency in PFM mode with a minimum quiescent current to maintain high efficiency. The

converter positions the output voltage typically +1% above the nominal output voltage. This voltage positioning

feature minimizes voltage drops caused by a sudden load step.

The transition from PWM mode to PFM mode occurs once the inductor current in the low-side MOSFET switch

becomes zero, which indicates discontinuous conduction mode.

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