(

)

IN

OUT

OUT

DS(on)

L

V min = V

max + I

max

R

max+ R

´

I

= 0.5 x I

OUT_PFM/PWM

LPFMpeak

IN

OUT

LPFMpeak

ONmin

(V

V

)

I

=

t

L

-

´

9

TPS62231-Q1, TPS622314-Q1

www.ti.com

SLVSB63A – DECEMBER 2011 – REVISED MARCH 2016

Product Folder Links: TPS62231-Q1 TPS622314-Q1

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Copyright © 2011–2016, Texas Instruments Incorporated

Device Functional Modes (continued)

•

(1)

Therefore, use Equation 2 to calculate the approximate peak inductor current in PFM mode.

where

•

•

L = Inductance (µH)

(2)

Use Equation 3 to estimate the transition from PFM into PWM mode and from PWM into PFM.

where

•

(mA)

(3)

7.4.3 Forced PWM Mode

Pulling the MODE pin high forces the converter to operate in a continuous-conduction PWM mode even at light

load currents. The advantage is that the converter operates with a quasi-fixed frequency that 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.

For additional flexibility, switch from power save mode to forced PWM mode during operation. This switching

allows for efficient power management by adjusting the operation of the converter to the specific system

requirements.

7.4.4 100% Duty-Cycle Low-Dropout Operation

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

voltage. To maintain the output voltage, the high-side switch is turned on 100% for one or more cycles.

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

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

Use Equation 4 to calculate the minimum input voltage to maintain regulation which is dependent on the load

current and output voltage.

where

•

•

•

•

(4)

7.4.5 Short-Circuit Protection

The device integrates a high-side and low-side MOSFET current limit to protect the device against heavy load or

short circuit. The current in the switches is monitored by current-limit comparators. When the current in the P-

channel MOSFET reaches the current limit, the P-channel MOSFET is turned off and the N-channel MOSFET is

turned on to ramp down the current in the inductor. The high-side MOSFET switch can only turn on again when

the current in the low-side MOSFET switch has decreased below the threshold of the current-limit comparator.