LP5523 datasheet(12/61 Pages) TI2

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LP5523

SNVS550E – SEPTEMBER 2009 – REVISED JANUARY 2017

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7.3 Feature Description

7.3.1 Programming

The LP5523 provides flexibility and programmability for dimming and sequencing control. Each LED can be

controlled directly and independently through the serial bus, or LED drivers can be grouped together for pre-

programmed flashing patterns.

The LP5523 has three independent program execution engines, so it is possible to form three independently

programmable LED banks. LED drivers can be grouped based on their function so that, for example, the first

bank of drivers can be assigned to the keypad illumination, the second bank to the funlights, and the third group

to the indicator LED(s).

Each bank can contain 1 to 9 LED driver outputs. Instructions for program execution engines are stored in the

program memory. The total amount of the program memory is 96 instructions, and the user can allocate the

memory as required by the engines.

7.3.2 LED Error Detection

The LP5523 has built-in LED error detection. Error detection does not only detect open and short circuit, but

provides an opportunity to measure the VF of the LEDs. The test event is activated by a serial interface write, and

the results can be read through the serial interface during the next cycle. This feature can also be addressed to

measure the voltage on VDD, VOUT, and INT pins. Typical example usage includes monitoring battery voltage

or using INT pin as a light sensor interface.

7.3.3 Energy Efficiency

When charge-pump automatic mode selection is enabled, the LP5523 monitors the voltage over the drivers of D1

to D6 so that the device can select the best charge-pump gain and maintain good efficiency over the whole

operating voltage range. The red LED element of an RGB LED typically has a forward voltage of about 2 V. For

that reason, the outputs D7, D8, and D9 are internally powered by VDD, since battery voltage is high enough to

drive red LEDs over the whole operating voltage range. This allows the driving of three RGB LEDs with good

efficiency because the red LEDs do not load the charge pump. The LP5523 is able to automatically enter power-

save mode when LED outputs are not active, thus lowering idle current consumption down to 10 µA (typical).

Also, during the down time of the PWM cycle (constant current output status is low), additional power savings

can be achieved when the PWM Powersave feature is enabled.

7.3.4 Temperature Compensation

The luminance of an LED is typically a function of its temperature even though the current flowing through the

LED remains constant. Because luminance is temperature dependent, many LED applications require some form

of temperature compensation to decrease luminance and color purity variations due to temperature changes. The

LP5523 has a built-in temperature-sensing element, and PWM duty cycle of the LED drivers changes linearly in

relationship to changes in temperature. User can select the slope of the graph (31 slopes) based on the LED

characteristics (see Figure 13). This compensation can be done either constantly, or only right after the device

wakes up from power-save mode, to avoid error due to self-heating of the device. Linear compensation is

considered to be practical and accurate enough for most LED applications.

LP5523 Datasheet(PDF) 12 Page - Texas Instruments

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