NXP LED CONTROLLERS User Manual

LED
CONTROLLERS

VOLTAGE-SWITCH DRIVERS AND
CONSTANT-CURRENT DRIVERS

LED CONTROLLERS OVERVIEW

LEDs are used in a wide range of applications, from low-end status indicators to high-end
video displays. System designers often need the ability to control these LEDs, but can’t afford
to tie up the system processor to do so. NXP’s LED controllers solve this problem, performing
a variety of control tasks while offloading the system processor. Having sent instructions to
the LED controller, the processor is free to engage in other tasks or go into a low-power state.

NXP’s LED controllers offer a variety of features needed in LED-driving applications. Some of these features include:

• Blinking and dimming capability

• Pulse-width modulation (PWM) for LED brightness control

• Color mixing capabilities

• Fast-mode Plus (Fm+) bi-directional communication channel with data transfer rate of up to 1 Mbit/s over the I2C-bus

• Ultra-fast-mode (UFm) uni-directional communication channel with data transfer rate of up to 5 Mbit/s over the I2C-bus

• SPI-compatible 3-wire serial uni-directional interface with data transfer rate of up to 25 Mbit/s over serial peripheral
interface (SPI)

• Different output drive types (push-pull, open-drain voltage switch or constant-current driver)

• Independent control of LEDs

The devices are classified in two groups: voltage-switch drivers and constant-current drivers. These groups are discussed below.

VOLTAGE-SWITCH DRIVERS

Voltage-switch output driver devices control the LED
connected to the output pin by switching the connection
to ground or supply on or off. A series resistor connected
between the LED and the device limits the current that
flows through the LED into the device.

Voltage-switch devices have the advantage of dissipating
the heat outside the device, in the series resistor. Therefore,
the device is insensitive to heat dissipation and is good for
driving multiple LEDs in series, with different forward-bias
voltages (Vf), from the same supply.

(a) Example Voltage-Switch Output Structure (b) Example Constant-Current Output Structure

CONSTANT-CURRENT DRIVERS

A current-regulated LED driver controls the current internally
which results in the LED light remaining constant even with
supply-voltage fluctuations. NXP constant-current LED drivers
are used for low-current luminary lighting applications
requiring accurate lighting control independent of supply
voltage, temperature, and LED forward-bias voltage.

The LED controllers are supported by application boards and daughter cards, an established manufacturing infrastructure
that supports high volumes and technical documents. NXP helps system designers make lighting affordable, in everything
from indoor consumer electronics and appliances to outdoor decorative lighting.

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