LP5520 datasheet(17/46 Pages) TI1

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Duty control

1 MHz clock

OVPCOMP

ERRORAMP

SLOPER

OLPCOMP

RESETCOMP

LOOPC

ACTIVE

LOAD

SWITCH

UVCOMP

IMAX

OCPCOMP

VIN

VOUT

LP5520

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SNVS440B – MAY 2007 – REVISED MARCH 2016

Product Folder Links: LP5520

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Figure 20 shows the boost topology with the protection circuitry. Four different protection schemes are

implemented:

1. Overvoltage protection: limits the maximum output voltage and:

–

Keeps the output below breakdown voltage.

–

Prevents boost operation if battery voltage is much higher than desired output.

2. Overcurrent protection: limits the maximum inductor current and:

–

Voltage over switching NMOS is monitored; voltages too high turn off the switch.

3. Feedback break protection: prevents uncontrolled operation if FB pin is disconnected.

4. Duty cycle limiting done with digital control.

Figure 20. Boost Converter Topology

7.3.3.1 Boost Control

User can set the boost converter to standby mode by writing the register bit <en_boost> low. When <en_boost>

is written high, the converter starts for 50 ms in low current PWM mode and then goes to normal PWM mode.

User can control the boost output voltage by boost output boost_output (05H) register.

Table 7. Boost Output Voltage Control

BOOST OUTPUT [7:0]

BOOST OUTPUT

VOLTAGE (TYPICAL)

Bin

Dec

00101

5 V

00110

6 V

00111

7 V

...

01100

12 V

01101

13 V

01110

14 V

...

10010

18 V

10011

19 V

10100

20 V

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