NXP PCA9635 16位RGBA彩色LED驱动方案

NXP 公司的PCA9635是I2C总线控制的16位红/绿/蓝/琥珀(RGBA)彩色LED驱动器,每个LED输出有8位分辨率(256级)的单独PWM控制器,工作频率97kHz,占空比从0%到99.6%可调,使LED设定特定的亮度.另外的8位分辨率群PWM控制器有固定频率190Hz和在24Hz到10.73秒的可调频率, 占空比从0%到99.6%可调. PCA9635主要用作RGB或RGBA LED驱动器,LED显示器,LCD背光以及手机或手提设备的键盘背景光.本文介绍了PCA9635主要特性, 方框图, 典型应用电路和开关时间测试电路.

PCA9635: 16-bit Fm+ I2C-bus LED driver

The PCA9635 is an I2C-bus controlled 16-bit LED driver optimized for Red/Green/Blue/Amber (RGBA) color mixing applications. Each LED output has its own 8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at 97 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightness value. An additional 8-bit resolution (256 steps) group PWM controller has both a fixed frequency of 190 Hz and an adjustable frequency between 24 Hz to once every 10.73 seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dim or blink all LEDs with the same value.

Each LED output can be off, on (no PWM control), set at its individual PWM controller value or at both individual and group PWM controller values. The LED output driver is programmed to be either open-drain with a 25 mA current sink capability at 5 V or totem-pole with a 25 mA sink, 10 mA source capability at 5 V. The PCA9635 operates with a supply voltage range of 2.3 V to 5.5 V and the outputs are 5.5 V tolerant. LEDs can be directly connected to the LED output (up to 25 mA, 5.5 V) or controlled with external drivers and a minimum amount of discrete components for larger current or higher voltage LEDs.

The PCA9635 is one of the first LED controller devices in a new Fast-mode Plus (Fm+) family. Fm+ devices offer higher frequency (up to 1 MHz) and more densely populated bus operation (up to 4000 pF).

The active LOW Output Enable input pin (OE) allows asynchronous control of the LED outputs and can be used to set all the outputs to a defined I2C-bus programmable logic state. The OE can also be used to externally PWM the outputs, which is useful when multiple devices need to be dimmed or blinked together using software control.

Software programmable LED Group and three Sub Call I2C-bus addresses allow all or defined groups of PCA9635 devices to respond to a common I2C-bus address, allowing for example, all red LEDs to be turned on or off at the same time or marquee chasing effect, thus minimizing I2C-bus commands. Seven hardware address pins allow up to 126 devices on the same bus.

The Software Reset (SWRST) Call allows the master to perform a reset of the PCA9635 through the I2C-bus, identical to the Power-On Reset (POR) that initializes the registers to their default state causing the outputs to be set HIGH (LED off). This allows an easy and quick way to reconfigure all device registers to the same condition.

PCA9635主要特性:

16 LED drivers. Each output programmable at:

Off

On

Programmable LED brightness

Programmable group dimming/blinking mixed with individual LED brightness

1 MHz Fast-mode Plus compatible I2C-bus interface with 30 mA high drive capability on SDA output for driving high capacitive buses

256-step (8-bit) linear programmable brightness per LED output varying from fully off(default) to maximum brightness using a 97 kHz PWM signal

256-step group brightness control allows general dimming (using a 190 Hz PWM signal) from fully off to maximum brightness (default)

256-step group blinking with frequency programmable from 24 Hz to 10.73 s and duty cycle from 0 % to 99.6 %

Sixteen totem-pole outputs (sink 25 mA and source 10 mA at 5 V) with software programmable open-drain LED outputs selection (default at totem-pole). No input function.

Output state change programmable on the Acknowledge or the STOP Command to update outputs byte-by-byte or all at the same time (default to ‘Change on STOP’).

Active LOW Output Enable (OE) input pin. LED outputs programmable to logic 1, logic 0 or ‘high-impedance’ (default at power-up) when OE is HIGH, thus allowing hardware blinking and dimming of the LEDs.

7 hardware address pins allow 126 devices to be connected to the same I2C-bus

4 software programmable I2C-bus addresses (one LED Group Call address and three LED Sub Call addresses) allow groups of devices to be addressed at the same time in any combination (for example, one register used for ‘All Call’ so that all the PCA9635s on the I2C-bus can be addressed at the same time and the second register used for three different addresses so that 13 of all devices on the bus can be addressed at the same time in a group). Software enable and disable for I2C-bus address.

Software Reset feature (SWRST Call) allows the device to be reset through the I2C-bus

25 MHz internal oscillator requires no external components

Internal power-on reset

Noise filter on SDA/SCL inputs

Edge rate control on outputs

No glitch on power-up

Supports hot insertion

Low standby current

Operating power supply voltage range of 2.3 V to 5.5 V

5.5 V tolerant inputs

40℃ to +85℃ operation

ESD protection exceeds 2000 V HBM per JESD22-A114, 200 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101

Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

Packages offered: TSSOP28

PCA9635应用:

RGB or RGBA LED drivers

LED status information

LED displays

LCD backlights

Keypad backlights for cellular phones or handheld devices


图1.PCA9635方框图


图2.PCA9635典型应用电路


图3.PCA9635开关时间测试电路