TPS62933O datasheet(18/47 Pages) TI

18 / 47 page

REF

(6)

where

• VREF = 0.8 V, the internal reference voltage

• ISS = 5.5 µA (typical), the internal pullup current

If the output capacitor is pre-biased at start-up, the device initiates switching and starts ramping up only after

the internal reference voltage becomes greater than the feedback voltage VFB. This scheme ensures that the

converters ramp up smoothly into regulation point.

A resistor divider is connected to the SS pin can implement voltage tracking of other power rail.

8.3.8 Minimum On Time, Minimum Off Time, and Frequency Foldback

Minimum on time (tON_MIN) is the smallest duration of time that the high-side switch can be on. tON_MIN is typical

70 ns in the TPS62933. Minimum off time (tOFF_MIN) is the smallest duration that the high-side switch can be

off. tOFF_MIN is typical 140 ns. In CCM operation, tON_MIN and tOFF_MIN limit the voltage conversion range without

switching frequency foldback.

The minimum duty cycle without frequency foldback allowed is:

DMIN = tON_MIN × fSW

(7)

The maximum duty cycle without frequency foldback allowed is:

DMAX = 1 F tOFF _MIN × fSW

(8)

Given a required output voltage, the maximum VIN without frequency foldback is:

VIN_MAX =

VOUT

fSW × tON _MIN

(9)

The minimum VIN without frequency foldback is:

VIN_MIN =

VOUT

1 F fSW × tOFF _MIN

(10)

In TPS62933, a frequency foldback scheme is employed once tON_MIN or tOFF_MIN is triggered, which can extend

the maximum duty cycle or lower the minimum duty cycle.

The on time decreases while VIN voltage increases. Once the on time decreases to tON_MIN, the switching

frequency starts to decrease while VIN continues to go up, which lowers the duty cycle further to keep VOUT in

regulation according to Equation 7.

The frequency foldback scheme also works once larger duty cycle is needed under low VIN condition. The

frequency decreases once the device hits its tOFF_MIN, which extends the maximum duty cycle according to

Equation 8. Wide range of frequency foldback allows the TPS62933 output voltage to stay in regulation with a

much lower supply voltage VIN, which allows a lower effective dropout.

With frequency foldback, VIN_MAX is raised, and VIN_MIN is lowered by decreased fSW.

TPS62933

SLUSEA4A – JUNE 2021 – REVISED DECEMBER 2021

www.ti.com

Submit Document Feedback

Product Folder Links: TPS62933

TPS62933O Datasheet(PDF) 18 Page - Texas Instruments

TPS62933O Datasheet(HTML) 18 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Datasheet Download

Link URL