(

)

IN(min)

OUT(min)

OUT

DS(on)

L

V

V

I

R

R

=

+

+

(

)

OUT

LPSM(pea

IN

ON

k)

V

V

t

L

I

-

´

=

OUT

ON

IN

V

t

420ns

V

=

´

TPS62160-Q1

www.ti.com

SLVSCK6 – DECEMBER 2014

Device Functional Modes (continued)

8.4.2 Power Save Operation

The TPS62160-Q1's built in Power Save Mode will be entered seamlessly, if the load current decreases. This

secures a high efficiency in light load operation. The device remains in Power Save Mode as long as the inductor

current is discontinuous.

In Power Save Mode the switching frequency decreases linearly with the load current maintaining high efficiency.

The transition into and out of Power Save Mode happens within the entire regulation scheme and is seamless in

both directions.

The TPS62160-Q1 includes a fixed on-time circuitry. This on-time, in steady-state operation, can be estimated

as:

space

(1)

space

For very small output voltages, the on-time increases beyond the result of Equation 1, to stay above an absolute

be approximated by:

space

(2)

space

regardless of the load current. The device maintains output regulation in PWM mode.

8.4.3 100% Duty-Cycle Operation

The duty cycle of the buck converter is given by D = Vout/Vin and increases as the input voltage comes close to

the output voltage. In this case, the device starts 100% duty cycle operation turning on the high-side switch

100% of the time. The high-side switch stays turned on as long as the output voltage is below the internal set

point. This allows the conversion of small input to output voltage differences, e.g. for longest operation time of

battery-powered applications. In 100% duty cycle mode, the low-side FET is switched off.

The minimum input voltage to maintain output voltage regulation, depending on the load current and the output

voltage level, can be calculated as:

space

(3)

where

space

8.4.4 Current Limit and Short Circuit Protection

The TPS62160-Q1 is protected against heavy load and short circuit events. At heavy loads, the current limit

determines the maximum output current. If the current limit is reached, the high-side FET will be turned off.

Avoiding shoot through current, the low-side FET will be switched on to sink the inductor current. The high-side

FET will turn on again, only if the current in the low-side FET has decreased below the low side current limit

threshold.

Copyright © 2014, Texas Instruments Incorporated

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