Nov 28, 2017: Analog Devices offers LT3964, a dual channel, 36V synchronous, step-down LED driver with internal 40V, 1.6A power switches, along with an I2C interface that makes LED dimming control easier.
The LT3964 has a wide 4V to 36V input range, and features two LED drivers that switch at up to 2MHz, leading to a highly integrated, compact solution with small external components. The LED driver employs fixed frequency, current mode control, and operates as a constant-current and constant-voltage source. It has accurate current regulation to provide optimal LED lighting in automotive, industrial and architectural lighting applications.
Its switching frequency is programmable from 200kHz to 2MHz; it can also be synchronized to an external clock signal. LED driver protection features include open LED and short-circuit LED fault detection, and LED overcurrent and overvoltage detection, all of which can be reported via the I 2C interface.
With synchronous operation, it offers 94% efficiency when both the channels are at full current load. Its 400kHz I 2C interface makes digital PWM dimming easier. In this product, a PWM signal from a microcontroller to the LED driver is not required. However, the internal registers have been programmed with the dimming cycle, which is synchronized to the internal clock.
As a result, the dimming ratios is up to 8192:1, and gets rid of beat frequencies caused when the PWM signal and the internal oscillator are not synchronized. Alternatively, with analog dimming, an I 2C settable 8-bit scale factor sets the control voltage-to-LED current ratio, and allows more control of analog dimming adjustments. 1000:1 external PWM dimming and 10:1 analog dimming are also provided.
The fixed frequency and peak current mode topology result in stable operation over a wide range of supply and output voltages. The ground referred voltage FB pin serves as the input for several LED protection features, and also allows the converter to operate as a constant-voltage source. The maximum output current is set by an external resistor, and the output current amplifier has a rail-to-rail common mode range. LT3964 uses an I 2C interface to communicate with a microcontroller to read LED faults, write PWM and analog dimming registers and set fault masking. The I2C PWM input provides LED dimming ratios up to 8192:1. The I2C programmable CTRL register sets the gain of the external CTRL pin, and maximum current sense threshold, providing additional analog dimming capability.
Source: Analog Devices – www.analog.com