LP8501 datasheet(13/51 Pages) TI1

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LP8501

www.ti.com

SNVS548D – SEPTEMBER 2008 – REVISED AUGUST 2013

FUNCTIONAL OVERVIEW

The LP8501 is a fully integrated lighting management unit (LMU) designed for producing lighting effects for

mobile devices. The LP8501 includes all necessary power management, high-side current sources, two-wire

control interface and programmable execution engines. The overall maximum current for each driver is set by an

8-bit register.

The LP8501 controls LED luminance with a pulse width modulation (PWM) scheme with a resolution of 12 bits.

Programming

The LP8501 provides flexibility and programmability for dimming and sequencing control. Each LED can be

controlled directly and independently through the serial bus. LED drivers can also be freely grouped together.

The LED drivers may be grouped into a maximum of three groups. Each of the three groups' PWM can be

controlled through the serial bus.

The LP8501 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 “fun lights” 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.

LED Error Detection

The LP8501 has built-in LED error detection. Error detection both detects open and short circuits, and provides

an opportunity to measure the forward voltages of the LEDs. The test is activated by serial interface write, and

the result can be read through the serial interface during the next cycle. This can be used for general purpose

measurements such as checking the supply voltages and charge pump output voltage.

Energy Efficiency

When charge pump automatic mode selection is enabled, the LP8501 monitors the voltage over the drivers

which are powered from the charge pump (VOUT) so that the device can select the best charge pump gain and

maintain good efficiency over the whole operating voltage range. In RGB LED applications the red LED element

typically has a forward voltage of about 2V. For that reason, the outputs D7, D8 and D9 can be powered by VDD

since battery voltage is high enough to drive red LEDs over the whole operating range. This allows driving of

three RGB LEDs with good efficiency because the red LEDs don't load the charge pump.

The LP8501 is able to automatically enter power-save mode, when LED outputs are not active, thus lowering idle

current consumption down to 10 µA (typ.). Also, during the "down time" of the PWM cycle (constant current

output status is low), additional power savings can be achieved under certain conditions.

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