OVP

Light

Load

SW

R

R

OCP

Switch

Driver

R

S

R

$

+

-

+

-

Osc/

ramp

gm

-

+

VREF

FB

Boost output

voltage

adjustment

Active Load

Startup

LP8553

www.ti.com

SNVS701B – SEPTEMBER 2011 – REVISED JANUARY 2014

Protection

Three different protection schemes are implemented:

1. Over-voltage protection, limits the maximum output voltage.

–

Over-voltage 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. Over-current protection, limits the maximum inductor current.

3. Duty cycle limiting.

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

0

10

00001

1

11

00010

2

12

00011

3

13

00100

4

14

...

...

...

11101

29

39

11110

30

40

11111

31

40

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 ~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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