NXP PCA9532 16位I2C LED调光方案
NXP 公司的PCA9532是16位I2C总线和SMBus I/O扩展器,最适合RGB色彩混合和背景光应用的LED调光(256步). PCA9532有16个LED驱动器,有两个可选择的全编程的闪光速率(0.591 Hz -152 Hz ),256亮度等级. I2C总线接口逻辑和SMBus兼容,内部有重起重置, SCL/SDA输入有噪音滤波器.本文介绍了PCA9532的主要特性,方框图以及典型应用框图.
PCA9532: 16-bit I2C-bus LED dimmer
The PCA9532 is a 16-bit I2C-bus and SMBus I/O expander optimized for dimming LEDs in 256 discrete steps for Red/Green/Blue (RGB) color mixing and back light applications.
The PCA9532 contains an internal oscillator with two user programmable blink rates and duty cycles coupled to the output PWM. The LED brightness is controlled by setting the blink rate high enough (> 100 Hz) that the blinking cannot be seen and then using the duty cycle to vary the amount of time the LED is on and thus the average current through the LED.
The initial setup sequence programs the two blink rates/duty cycles for each individual PWM. From then on, only one command from the bus master is required to turn individual LEDs ON, OFF, BLINK RATE 1 or BLINK RATE 2. Based on the programmed frequency and duty cycle, BLINK RATE 1 and BLINK RATE 2 will cause the LEDs to appear at a different brightness or blink at periods up to 1.69 second. The open-drain outputs directly drive the LEDs with maximum output sink current of 25 mA per bit and 200 mA per package (100 mA per octal).
To blink LEDs at periods greater than 1.69 second the bus master (MCU, MPU, DSP,chip set, etc.) must send repeated commands to turn the LED on and off as is currently done when using normal I/O expanders like the NXP Semiconductors PCF8575 or PCA9555. Any bits not used for controlling the LEDs can be used for General Purpose parallel Input/Output (GPIO) expansion, which provides a simple solution when additional I/O is needed for ACPI power switches, sensors, push-buttons, alarm monitoring, fans,etc.
The active LOW hardware reset pin (RESET) and Power-On Reset (POR) initializes the registers to their default state, all zeroes, causing the bits to be set HIGH (LED off).
Three hardware address pins on the PCA9532 allow eight devices to operate on the same bus.
PCA9532主要特性:
16 LED drivers (on, off, flashing at a programmable rate)
Two selectable, fully programmable blink rates (frequency and duty cycle) between 0.591 Hz and 152 Hz (1.69 second and 6.58 milliseconds)
256 brightness steps
Input/outputs not used as LED drivers can be used as regular GPIOs
Internal oscillator requires no external components
I2C-bus interface logic compatible with SMBus
Internal power-on reset
Noise filter on SCL/SDA inputs
Active LOW reset input
16 open-drain outputs directly drive LEDs to 25 mA
Controlled edge rates to minimize ground bounce
No glitch on power-up
Supports hot insertion
Low standby current
Operating power supply voltage range of 2.3 V to 5.5 V
0 Hz to 400 kHz clock frequency
ESD protection exceeds 2000 V HBM per JESD22-A114, 150 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: SO24, TSSOP24, HVQFN24
图1.PCA9532方框图
图2.PCA9532典型应用框图
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