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I2C LED controllers
Introduction
I2C LED controllers are most commonly used for blinking, dimming, and color mixing LEDs in I2C, SMBus, IPMI, and PMBus applications.
Using a separate I2C LED controller limits bus traffic and frees up the I2C Master (MCU, MPU, DSP, chipset, etc.) timer.
LED Dimmers and Blinkers
To blink or dim LEDs using normal general purpose I/O expanders like the PCF8574 or PCA9554, the bus master must send repeated commands to turn the LED on and off.
This greatly increases the amount of traffic on the I2C bus and uses up one of the master's timers.
The PCA9550, PCA9551, PCA9552, and PCA9553 LED blinkers instead require only the initial set up command to program the frequency and duty cycle (i.e., blink rate) for each individual port as BLINK RATE 1 and BLINK RATE 2.
From then on, the controller only requires one command from the bus master to turn the individual LEDs ON, OFF, or to blink at BLINK RATE 1 or BLINK RATE 2.
These unique LED controllers have an internal oscillator that is accurate to ±15% with the two programmable blink rates.
The blinking rates are adjustable between 40Hz and 6.4 seconds.
The PCA9530, PCA9531, PCA9532, and PCA9533 LED dimmers are similar to the blinkers but have a frequency adjustable between 160Hz and 1.6 seconds.
Our LED dimmers can be used to dim LEDs (e.g., for backlights) by running at the maximum blink rate and then varying duty cycle between 0 and 100%.
An additional benefit is that any bits that are not used for controlling the LEDs can be used for General Purpose Input/Output (GPIO) expansion.
I/O expansion provides a simple solution when additional I/O is needed for ACPI power switches, sensors, pushbuttons, alarm monitoring, fans, etc.
- 2.3V to 5.5V operating voltage with 5V-tolerant I/Os
- -40 °C to 85 °C operating temperature range
- 0kHz to 400kHz clock frequency
- I2C and SMBus compatible
- Two user-programmable blink rates and duty cycles
- Blink rates between 40Hz and 6.4 seconds or between 160Hz and 1.6 seconds
- Duty cycle between 0% and 100%
- Internal oscillator is accurate to ±15% and requires no external components
- Open drain outputs can directly drive LEDs up to 25mA sink per bit
- Maximum device limits of 50mA for the PCA9530/50, 100mA for the PCA9531/33/51/53, and 200mA (100mA per 8-bit group) for the PCA9532/52
- Input/Output states readable via I2C/SMBus
- Any bit not used to drive an LED can be used as a normal GPIO
- Active low hardware reset (RESET) or Power On Reset (POR) initializes the registers to their default state, all zeroes, causing all the channels to be deselected
- Low standby current (Istb) of 1.5uA max
- Offered in SO (D), TSSOP (DP or PW), and HVQFN (BS)
LED Drivers/RGBA Mixers
The PCA9625/32/33/34/35 LED controllers have a 256-step PWM for each bit to allow individual dimming control of every LED and an extra PWM to allows for overall dimming or blinking of all the outputs.
These devices also have the new Fast Mode Plus I2C-bus interface allowing up to 1MHz operation to 540pF bus capacitance.
It supports lower frequencies on buses loaded up to 4000pF which makes it ideal for bus-based applications.
- Able to sink 25mA per bit
- Individual 256-step PWMs for dimming each LED
- One extra 256-step PWM for dimming or blinking of all LEDs
- One user-programmable dim/blink rate of 190Hz or between 24Hz to 10.73 sec
The PCA9632 is a lower-speed oscillator version of the PCA9633 for mobile applications.
The PCA9625 is a higher current and voltage version of the PCA9635 for gaming applications
LED Segment Drivers
The SAA1064 is a 32-bit LED controller with an I2C bus.
The LED controller is a bipolar integrated circuit made in an I2L-compatible 18v process.
This product is optimized to drive four 7-segment LED displays with decimal point by means of multiplexing between two pairs of digits.
It features an I2C-bus slave transceiver interface with the possibility to program four different SLAVE ADDRESSES, a POWER RESET flag, 16 current sink OUTPUTS (controllable by software up to 21mA), two multiplex drive outputs for common anode segments, an on-chip multiplex oscillator, control bits to select static/dynamic/blank modes, and one bit for segment test.
Additionally, it can be used to control LEDs.
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I2C LED Controllers
Literature
 | Bright ideas for LED applications LED solutions for gaming, mobile, signage, LCD TV backlighting, LED indication, and more © October 2007; English; Ordering code: 9397 750 16133 |
 | LED dimming with GPIO expansion NXP 2/4/8/16-bit I2C/SMBus LED dimmers PCA9530/31/32/33 © June 2007; English; Ordering code: 9397 750 16073 |
 | LED blinking with GPIO expansion NXP 2/4/8/16-bit I2C/SMBus LED blinkers PCA9550/51/52/53 © June 2007; English; Ordering code: 9397 750 16021 |
 | Color-mixing RGB LED drivers for mobile, entertainment, and architectural lighting NXP I2C RGB LED dimmers PCA963x © March 2007; English; Ordering code: 9397 750 15809 |
 | Longer standby times in mobile and portable applications NXP one-wire single LED driver for cell phones PCA9901 © March 2007; English; Ordering code: 9397 750 15807 |
 | Easily test and demonstrate LED dimming and blinking NXP demo board for Fast-mode Plus 4-bit I2C LED controller PCA9633 © January 2007; English; Ordering code: 9397 750 15907 |
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