LP8551TLX-ASLASHNOPB.A datasheet(17/46 Pages) TI2

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OVP

Light

Load

OCP

Switch

Driver

Osc/

ramp

VREF

Boost output

voltage

adjustment

Active Load

Startup

LP8551

www.ti.com

SNVS673E – APRIL 2010 – REVISED SEPTEMBER 2014

Figure 12. Boost Topology with Protection Circuitry

8.3.3.2 Protection

Three different protection schemes are implemented:

1. Overvoltage protection, limits the maximum output voltage.

–

Overvoltage protection limit changes dynamically based on output voltage setting.

–

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.

3. Duty cycle limiting.

8.3.3.3 Manual Output Voltage Control

User can control the boost output voltage with <VBOOST[4:0]> EEPROM register bits when adaptive mode is

disabled.

VBOOST[4:0]

VOLTAGE (TYPICAL)

BIN

DEC

VOLTS

00000

00001

00010

00011

00100

...

11101

11110

11111

8.3.3.4 Adaptive Boost Control

Adaptive boost control function adjusts the boost output voltage to the minimum sufficient voltage for proper LED

driver operation. The output with highest VF LED string is detected and boost output voltage adjusted

accordingly. Driver headroom can be adjusted with <DRIVER_HEADR[2:0]> EEPROM bits from approximately

300 mV to 1200 mV. Boost adaptive control voltage step size is 125 mV. Boost adaptive control operates

similarly with and without PSPWM.

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