V

I

(min) + VO(max) ) IO(max)

r

DS(on)

(max) ) RL

, nominal

0.8%

1.6%

–1.6%

t

VO

TPS62052, TPS62054

TPS62056, TPS62050, TPS62051

www.ti.com

SLVS432E – SEPTEMBER 2002 – REVISED JUNE 2011

Figure 17. Power-Save Mode Output Voltage Thresholds

The converter enters the fixed frequency PWM mode again as soon as the output voltage falls below the comp

Soft-Start

The TPS6205x has an internal soft-start circuit that limits the inrush current during start-up. This prevents

possible voltage drops of the input voltage if a battery or a high impedance power source is connected to the

input of the TPS6205x.

The soft-start is implemented as a digital circuit increasing the switch current in steps of 200 mA, 400 mA, 800

mA and then the typical switch current limit of 1.2 A. Therefore the start-up time mainly depends on the output

capacitor and load current. Typical start-up time with a 22-µF output capacitor and a 200-mA load current is 1

ms.

100% Duty Cycle Low Dropout Operation

The TPS6205x offers the lowest possible input to output voltage difference while still maintaining operation with

the use of the 100% duty cycle mode. In this mode, the P-channel switch is constantly turned on. This is

particularly useful in battery powered applications to achieve longest operation time by taking full advantage of

the whole battery voltage range, i.e. The minimum input voltage to maintain regulation depends on the load

current and output voltage and can be calculated as:

Enable and Overtemperature Protection

Logic low on EN forces the TPS6205x into shutdown. In shutdown, the power switch, drivers, voltage reference,

oscillator, and all other functions are turned off. The supply current is reduced to less than 2 µA in the shutdown

mode. When the device is in thermal shutdown, the bandgap is forced to stay on even if the device is set into

shutdown by pulling EN to GND. As soon as the temperature drops below the threshold, the device automatically

starts again.

If an output voltage is present when the device is disabled, which could be an external voltage source or super

cap, the reverse leakage current is specified under electrical characteristics. Pulling the enable pin high starts up

the TPS6205x with the soft-start as described under the paragraph soft-start. If the EN pin is connected to any

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