PCA9685PW,118

The PCA9685PW,118 is an I²C-bus controlled 16-channel LED controller optimized forRed/Green/Blue/Amber (RGBA) color backlighting applications. Each LED output has itsown 12-bit resolution (4096 steps) fixed frequency individual PWM controller that operatesat a programmable frequency from a typical of 24 Hz to 1526 Hz with a duty cycle that isadjustable 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 controllervalue. The LED output driver is programmed to be either open-drain with a 25 mA currentsink capability at 5 V or totem pole with a 25 mA sink, 10 mA source capability at 5 V. ThePCA9685PW,118 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs andoutputs are 5.5 V tolerant. LEDs can be directly connected to the LED output (up to25 mA, 5.5 V) or controlled with external drivers and a minimum amount of discretecomponents for larger current or higher voltage LEDs.

The PCA9685PW,118 is in the new Fast-mode Plus (Fm+) family. Fm+ devices offer higherfrequency (up to 1 MHz) and more densely populated bus operation (up to 4000 pF).

Although the PCA9635 and PCA9685PW,118 have many similar features, the PCA9685PW,118 has features that make it more suitable for applications such as LCD or LEDbacklighting and Ambilight:

• The PCA9685PW,118 allows staggered LED output on and off times to minimize currentsurges. The on and off time delay is independently programmable for each of the16 channels. This feature is not available in PCA9635
• The PCA9685PW,118 has 4096 steps (12-bit PWM) of individual LED brightness control. ThePCA9635 has only 256 steps (8-bit PWM)
• When multiple LED controllers are incorporated in a system, the PWM pulse widthsbetween multiple devices may differ if PCA9635s are used. The PCA9685PW,118 has aprogrammable prescaler to adjust the PWM pulse widths of multiple devices
• The PCA9685PW,118 has an external clock input pin that will accept user-supplied clock(50 MHz max.) in place of the internal 25 MHz oscillators. This feature allowssynchronization of multiple devices. The PCA9635 does not have an external clock inputfeature
• Like the PCA9635, PCA9685PW,118 also has a built-in oscillator for the PWM control.However, the frequency used for PWM control in the PCA9685PW,118 is adjustable fromabout 24 Hz to 1526 Hz as compared to the typical 97.6 kHz frequency of thePCA9635. This allows the use of PCA9685PW,118 with external power supply controllers. Allbits are set at the same frequency
• The Power-On Reset (POR) default state of LEDn output pins is LOW in the case ofPCA9685. It is HIGH for PCA9635

The active LOW Output Enable input pin (OE) allows asynchronous control of the LEDoutputs and can be used to set all the outputs to a defined I²C-bus programmable logicstate. The OE can also be used to externally ‘pulse width modulate’ the outputs, which isuseful when multiple devices need to be dimmed or blinked together using softwarecontrol.

Software programmable LED All Call and three Sub Call I²C-bus addresses allow all ordefined groups of PCA9685PW,118 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 chasingeffect, thus minimizing I²C-bus commands. Six hardware address pins allow up to62 devices on the same bus.

The Software Reset (SWRST) General Call allows the master to perform a reset of thePCA9685PW,118 through the I²C-bus, identical to the Power-On Reset (POR) that initializes theregisters to their default state causing the outputs to be set LOW. This allows an easy andquick way to reconfigure all device registers to the same condition via software.

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