TPS54560 datasheet(13/46 Pages) TI1

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Vout

0.8V

= R

0.8 V

´ ç

4.7

0.1

0.15

0.35

0.5

Load Current - A

Start

Stop

4.8

4.9

5.1

5.3

4.6

5.4

5.5

5.6

5.2

0.05

0.25

0.2

0.3

0.4

0.45

Dropout

Voltage

Dropout

Voltage

TPS54560

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SLVSBN0B – MARCH 2013 – REVISED AUGUST 2016

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Feature Description (continued)

•

VBOOT = (1.41 x VIN - 0.554 - VF / TSW - 1.847 x 10

3 x IB2SW) / (1.41 + 1 / Tsw)

•

RDS(on) = 1 / (-0.3 x VB2SW

2 + 3.577 x VB2SW - 4.246)

(1)

Figure 23. 5V Start/Stop Voltage

8.3.5 Error Amplifier

The TPS54560 voltage regulation loop is controlled by a transconductance error amplifier. The error amplifier

compares the FB terminal voltage to the lower of the internal soft-start voltage or the internal 0.8 V voltage

reference. The transconductance (gm) of the error amplifier is 350 μA/V during normal operation. During soft-

start operation, the transconductance is reduced to 78 μA/V and the error amplifier is referenced to the internal

soft-start voltage.

The frequency compensation components (capacitor, series resistor and capacitor) are connected between the

error amplifier output COMP terminal and GND terminal.

8.3.6 Adjusting the Output Voltage

The internal voltage reference produces a precise 0.8 V ±1% voltage reference over the operating temperature

and voltage range by scaling the output of a bandgap reference circuit. The output voltage is set by a resistor

divider from the output node to the FB terminal. It is recommended to use 1% tolerance or better divider

resistors. Select the low side resistor RLS for the desired divider current and use Equation 2 to calculate RHS. To

improve efficiency at light loads consider using larger value resistors. However, if the values are too high, the

regulator will be more susceptible to noise and voltage errors from the FB input current may become noticeable.

(2)

8.3.7 Enable and Adjusting Undervoltage Lockout

The TPS54560 is enabled when the VIN terminal voltage rises above 4.3 V and the EN terminal voltage exceeds

the enable threshold of 1.2 V. The TPS54560 is disabled when the VIN terminal voltage falls below 4 V or when

the EN terminal voltage is below 1.2 V. The EN terminal has an internal pull-up current source, I1, of 1.2 μA that

enables operation of the TPS54560 when the EN terminal floats.

If an application requires a higher undervoltage lockout (UVLO) threshold, use the circuit shown in Figure 24 to

adjust the input voltage UVLO with two external resistors. When the EN terminal voltage exceeds 1.2 V, an

additional 3.4 μA of hysteresis current, IHYS, is sourced out of the EN terminal. When the EN terminal is pulled

below 1.2 V, the 3.4 μA Ihys current is removed. This additional current facilitates adjustable input voltage UVLO

hysteresis. Use Equation 3 to calculate RUVLO1 for the desired UVLO hysteresis voltage. Use Equation 4 to

calculate RUVLO2 for the desired VIN start voltage.

TPS54560 Datasheet(PDF) 13 Page - Texas Instruments

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