PCA9685 16-channel, 12-bit PWM Fm+ I2C-bus LED controllerRev. 4 — 16 April 2015Product data sheet1. Generaldescription The PCA9685 is an I2C-bus controlled 16-channel LED controller optimized for Red/Green/Blue/Amber (RGBA) color backlighting applications. Each LED output has its own 12-bit resolution (4096 steps) fixed frequency individual PWM controller that operates at a programmable frequency from a typical of 24 Hz to 1526 Hz with a duty cycle that is adjustable from 0 % to 100 % to allow the LED to be set to a specific brightness value. All outputs are set to the same PWM frequency. Each LED output can be off or on (no PWM control), or set at its individual PWM controller value. 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 PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and 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 PCA9685 is in the 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). Although the PCA9635 and PCA9685 have many similar features, the PCA9685 has some unique features that make it more suitable for applications such as LCD or LED backlighting and Ambilight: • The PCA9685 allows staggered LED output on and off times to minimize current surges. The on and off time delay is independently programmable for each of the 16 channels. This feature is not available in PCA9635. • The PCA9685 has 4096 steps (12-bit PWM) of individual LED brightness control. The PCA9635 has only 256 steps (8-bit PWM). • When multiple LED controllers are incorporated in a system, the PWM pulse widths between multiple devices may differ if PCA9635s are used. The PCA9685 has a programmable prescaler to adjust the PWM pulse widths of multiple devices. • The PCA9685 has an external clock input pin that will accept user-supplied clock (50 MHz max.) in place of the internal 25 MHz oscillator. This feature allows synchronization of multiple devices. The PCA9635 does not have external clock input feature. • Like the PCA9635, PCA9685 also has a built-in oscillator for the PWM control. However, the frequency used for PWM control in the PCA9685 is adjustable from about 24 Hz to 1526 Hz as compared to the typical 97.6 kHz frequency of the PCA9635. This allows the use of PCA9685 with external power supply controllers. All bits are set at the same frequency. • The Power-On Reset (POR) default state of LEDn output pins is LOW in the case of PCA9685. It is HIGH for PCA9635. Document Outline 1. General description 2. Features and benefits 3. Applications 4. Ordering information 4.1 Ordering options 5. Block diagram 6. Pinning information 6.1 Pinning 6.2 Pin description 7. Functional description 7.1 Device addresses 7.1.1 Regular I2C-bus slave address 7.1.2 LED All Call I2C-bus address 7.1.3 LED Sub Call I2C-bus addresses 7.1.4 Software Reset I2C-bus address 7.2 Control register 7.3 Register definitions 7.3.1 Mode register 1, MODE1 7.3.1.1 Restart mode 7.3.2 Mode register 2, MODE2 7.3.3 LED output and PWM control 7.3.4 ALL_LED_ON and ALL_LED_OFF control 7.3.5 PWM frequency PRE_SCALE 7.3.6 SUBADR1 to SUBADR3, I2C-bus subaddress 1 to 3 7.3.7 ALLCALLADR, LED All Call I2C-bus address 7.4 Active LOW output enable input 7.5 Power-on reset 7.6 Software reset 7.7 Using the PCA9685 with and without external drivers 8. Characteristics of the I2C-bus 8.1 Bit transfer 8.1.1 START and STOP conditions 8.2 System configuration 8.3 Acknowledge 9. Bus transactions 10. Application design-in information 11. Limiting values 12. Static characteristics 13. Dynamic characteristics 14. Test information 15. Package outline 16. Handling information 17. Soldering of SMD packages 17.1 Introduction to soldering 17.2 Wave and reflow soldering 17.3 Wave soldering 17.4 Reflow soldering 18. Abbreviations 19. Revision history 20. Legal information 20.1 Data sheet status 20.2 Definitions 20.3 Disclaimers 20.4 Trademarks 21. Contact information 22. Contents
