LP8553 datasheet(18/42 Pages) TI1

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EEPROM

NVM

8 x 8 bits

REGISTERS

ADDRESS 00h...72h

Startup or

EE_READ=1

User

Device Control

EEPROM

REGISTERS

Address A0h...A7h

EE_PROG = 1

Device Control

LP8553

SNVS701B – SEPTEMBER 2011 – REVISED JANUARY 2014

www.ti.com

Driver Headroom Control

Driver headroom can be controlled with <DRV_HEADR[2:0]> EEPROM bits. Driver headroom control sets the

minimum threshold for the voltage over the LED output which has the smallest driver headroom and controls the

boost output voltage accordingly. Boost output voltage step size is 125 mV. The LED output which has the

smallest forward voltage is the one which has highest VF across the LEDs. The strings with highest forward

voltage is detected automatically. To achieve best possible efficiency smallest possible headroom voltage should

be selected. If there is high variation between LED strings, the headroom can be raised slightly to prevent any

visual artifacts.

EEPROM

EEPROM memory stores various parameters for chip control. The 64-bit EEPROM memory is organized as 8 x 8

bits. The EEPROM structure consists of a register front-end and the non-volatile memory (NVM). Register data

can be read and written through the serial interface, and data will be effective immediately. To read and program

NVM, separate commands need to be sent. Erase and program voltages are generated on-chip charge pump, no

other voltages than normal input voltage are required. A complete EEPROM memory map is shown in the

chapter LP8553 Table 3.

NOTE

EEPROM NVM can be programmed or read by customer for bench validation.

Programming for production devices should be done in TI production test, where

appropriate checks will be performed to confirm EEPROM validity. Writing to EEPROM

Control register of production devices (for burning or reading EEPROM) is not

recommended. If special EEPROM configuration is required, please contact the TI Sales

Office for availability.

Boost Converter

Operation

The LP8553 boost DC/DC converter generates a 10…40V supply voltage for the LEDs from 2.7…22V input

voltage. The output voltage can be controlled either with EEPROM register bits <VBOOST[4:0]> or automatic

adaptive voltage control can be used. The converter is a magnetic switching PWM mode DC/DC converter with a

current limit. The topology of the magnetic boost converter is called CPM (current programmed mode) control,

where the inductor current is measured and controlled with the feedback. Switching frequency is selectable

between 156 kHz and 1.25 MHz with EEPROM bit <BOOST_FREQ[1:0]>. When <EN_BOOST> EEPROM

In adaptive mode the boost output voltage is adjusted automatically based on LED driver headroom voltage.

Boost output voltage control step size is in this case 125 mV to ensure as small as possible driver headroom and

high efficiency. Enabling the adaptive mode is done with <EN_ADAPT> EEPROM bit. If boost is started with

adaptive mode enabled, then the initial boost output voltage value is defined with the <VBOOST[4:0]> EEPROM

following figure shows the boost topology with the protection circuitry:

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