TPS62933O datasheet(23/47 Pages) TI

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Vin (V)

4.5

5.5

6.5

7.5

3.5

4.5

5.5

Io=0.5A

Io=3A

Figure 8-9. Overall Dropout Characteristic, VOUT = 5 V

8.4.5 Minimum On-Time Operation

Every switching converter has a minimum controllable on time dictated by the inherent delays and blanking

times associated with the control circuits. This imposes a minimum switch duty cycle and, therefore, a minimum

conversion ratio. The constraint is encountered at high input voltages and low output voltages. To help extend

the minimum controllable duty cycle, the TPS62933 automatically reduces the switching frequency when the

minimum on-time limit is reached. This way, the converter can regulate the lowest programmable output voltage

at the maximum input voltage. Use Equation 13 to find an estimate for the approximate input voltage for a given

output voltage before frequency foldback occurs. The values of tON_MIN and ƒSW can be found in Section 7.5.

VIN ”

VOUT

tON_MIN × fSW

(13)

As the input voltage is increased, the switch on time (duty-cycle) reduces to regulate the output voltage. When

the on time reaches the minimum on time, tON_MIN, the switching frequency drops while the on time remains

fixed.

8.4.6 Shutdown Mode

The EN pin provides electrical ON and OFF control for the device. When VEN is below typical 1.1 V, the

TPS62933 is in shutdown mode. The device also employs VIN UVLO protection. If VIN voltage is below their

respective UVLO level, the converter is turned off too.

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TPS62933

SLUSEA4A – JUNE 2021 – REVISED DECEMBER 2021

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TPS62933O Datasheet(PDF) 23 Page - Texas Instruments