Summary of Driving nine LEDs on a power budget, says ams
The AS3661 is a 9-channel, high-efficiency LED driver for mobile devices with an adaptive charge pump, three independent program engines, internal program memory, and I2C control. It offers 12-bit PWM per channel, up to 25.5 mA per output, automatic power-save mode (IVDD ≈ 10 μA), GPO and INT pins, and requires only four ceramic capacitors. The device supports autonomous operation, LED testing, and synchronization between multiple units for advanced lighting effects.
Parts used in the AS3661 LED driver project:
- AS3661 9-channel LED driver IC
- Four small ceramic capacitors
- LEDs (up to nine channels)
- Host processor or I2C master (optional for control)
- Wiring/traces for I2C, GPO, INT, and trigger pins
- Power source: Li-Ion battery (or equivalent supply)
Description
The AS3661 is a 9-channel LED driver designed to produce lighting effects for mobile devices. A highefficiency charge pump enables LED driving over full LiIon battery voltage range. The device is equipped with an internal program memory, which allows operation without processor control. The AS3661 maintains excellent efficiency over a wide operating range by autonomously selecting the best charge pump gain based on LED forward voltage requirements. AS3661 is able to automatically enter power-save mode when LED outputs are not active, thus lowering idle current consumption down to 10 μA (typ).
The AS3661 has an I2C-compatible control interface with four pin selectable addresses. Also, the device has a flexible General Purpose Output (GPO), which can be used as a digital control pin for other devices. INT pin can be used to notify processor when a lighting sequence has ended (interrupt – function). Also, the device has a trigger input interface, which allows synchronization between multiple devices.The device requires only four small and low-cost ceramic capacitors.
Key Features
- Three independent program execution engines; 9 programmable outputs with 25.5 mA full-scale current, 8- bit current setting resolution and 12-bit PWM control resolution
- Adaptive charge pump with 1x and 1.5x gain provides up to 95% LED drive efficiency
- Charge pump with soft start and overcurrent/short circuit protection
- Built-in LED test
- Automatic power save mode; IVDD = 10 μA (typ.)
- Two wire, I2C-compatible, control interface
- Flexible instruction set
- Large SRAM program memory
- Small application circuit
- Source (high side) drivers
- Minimum number of external components
- Architecture supports color control
An LED driver has been designed by ams which controls up to nine LEDs while saving power in LTE mobile devices because it operates independent of the baseband processor.
Typically used for indicator lighting, the AS3661 allows command-based programming of all light patterns.
Three independent program execution engines form three independently programmable LED banks which can be grouped based on their function.
Each bank can contain from one to nine LED driver outputs; the AS3661 offers nine LED channels in total with up to 25mA per channel. A dedicated 12-bit PWM for each of the nine channels delivers absolutely smooth color transitions and enables the production of linear, logarithmic and ratiometric fading effects.
Instructions for the program execution engines are stored in the program memory. The total capacity of the program memory is 96 instructions and the user can allocate a memory of 1.5kbit as re-quired by the engines.
“Our AS3661 smartlight driver enables systems designers to offer users more eye-catching effects and functionality than ever before. This new product truly brings color into the life of portable devices,” said Ronald Tingl, senior marketing manager of opto-electronic products at ams.
For more read: Driving nine LEDs on a power budget, says ams
- How many LED channels does the AS3661 support?
The AS3661 supports nine programmable LED channels. - Can the AS3661 operate without a processor?
Yes, it has internal program memory and three execution engines allowing operation without processor control. - What is the maximum current per channel?
Each channel supports up to 25.5 mA full-scale current (about 25 mA noted). - Does the AS3661 have a power-save mode?
Yes, it can automatically enter power-save mode with IVDD = 10 μA (typical). - What control interface does the AS3661 use?
It uses a two-wire, I2C-compatible control interface with four pin-selectable addresses. - How many bits of PWM resolution does each channel have?
Each channel has a 12-bit PWM control resolution. - What external components are required?
The device requires only four small, low-cost ceramic capacitors. - Can multiple AS3661 devices be synchronized?
Yes, it has a trigger input interface that allows synchronization between multiple devices. - Does the AS3661 include LED test and protection features?
Yes, it includes a built-in LED test and charge pump protections such as soft start and overcurrent/short circuit protection.
