LP8501 datasheet(18/51 Pages) TI1

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LP8501

SNVS548D – SEPTEMBER 2008 – REVISED AUGUST 2013

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Powering LEDs

The power for the LEDs is supplied via VDD1_6 (outputs D1 to D6) and VDD7_9 pins (outputs D7 and D9).

Powering LEDs this way allows flexibility since the pins can be connected to the VDD or to the VOUT (or to another

application power source, for example, an external DC/DC converter may be used), depending on the

application.

In the case of LEDs which have forward voltages around 2 volts, LEDs can be powered directly from VDD. If all

the LEDs are powered from VDD or an external power source and VOUT is not used the charge pump can be left

unconnected and charge pump capacitors can be left uninstalled. When the forward voltage of the LEDs is

around 3.6V, VDD may not be high enough. In this case the LEDs should be powered from the VOUT.

Note that the power supply must be correctly defined in the LP8501 register settings (register

05h 'Power

Config').

Controlling the PWM of High-Side LED Drivers

1. Direct PWM Control

–

All LP8501 LED drivers, D1 to D9, can be controlled independently through the two-wire serial I2C

compatible interface. For each high-side driver there is a PWM control register. Direct PWM control is

active by default.

2. Controlling by Program Execution Engines

–

Engine control is used when the user wants to create programmed sequences. Th program execution

engine has higher priority than direct control registers. Therefore, if the user has set a certain value to the

PWM register, it will be automatically overridden when the program execution engine controls the driver.

LED control and program execution engine operation is described later on in this document.

3. Group Fader Control

–

In addition to LED-by-LED PWM register control, the LP8501 is equipped with group fader control, which

allows the user to fade in or fade out multiple LEDs by writing to only one register. This is a useful

function to minimize serial bus traffic between the MCU and the LP8501. The LP8501 has three group

fader registers, so it is possible to form three fader groups.

–

With the LP8501 it is also possible to set fade-in and fade-out times. These times control the time when

ramping up or down the group PWM value. Time can be set with 4-bits according to the following table.

FADE IN/FADE OUT

Time (s)

0000

0.0

0001

0.05

0010

0.1

0011

0.2

0100

0.3

0101

0.4

0110

0.5

0111

0.6

1000

0.7

1001

0.8

1010

0.9

1011

1.0

1100

1.5

1101

2.0

1110

3.0

1111

4.0

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