Analog Devices Ltd

The LT3955 is a DC/DC converter designed to operate as a constant-current source and constant-voltage regulator with an internal 3.5A switch.The device's internal PWM dimming generator makes it ideal for driving high current LEDs and is also able to charge batteries and supercapacitors. The 4.5V to 60V input voltage range suits a wide variety of applications, including automotive, industrial and architectural lighting. The LT3955 uses an internal 3.5A, 80V N-channel MOSFET and can drive up to twelve 300mA white LEDs from a nominal 12V input delivering in excess of 20 watts. It incorporates a high-side current sense enabling use in boost mode, buck mode, buck-boost mode or SEPIC topologies. It can deliver efficiencies of over 94% in the boost topology eliminating the need for external heat sinking. The user can program the frequency between 100kHz and 1MHz, optimizing efficiency while minimizing external component size and cost. It offers a highly compact high power LED driver solution. The LT3955 has an internal PWM generator that delivers dimming ratios as high as 25:1 or it can utilise an external PWM signal, delivering dimming ratios of up to 3,000:1. For less demanding dimming requirements it can provide a 10:1 analog dimming range. Its fixed frequency, current-mode architecture offers stable operation over a wide range of supply and output voltages. Output short-circuit protection and open LED protection enhance system reliability. The ground-referenced voltage FB pin serves as the input for several LED protection features and makes it possible for the converter to operate as a constant-voltage source for charging applications. The LT3955 is available in a 36-lead 5mm x 6mm QFN package, pricing starts at $3.75 each. An extended temperature version is priced starting at $4.41 each for 1,000-piece quantities.

The LT1684 is a telecommunication ring tone generator. The IC takes a user-generated pulse width modulated (PWM) input and converts it to a high voltage sine wave suitable for telephone ringing applications.The LT1684 receives capacitor-isolated differential PWM input signals encoded with desired ring output cadence, frequency, and amplitude information. The LT1684 normalizes the pulse amplitude to +/-1.25V for an accurate signal voltage reference. The cadence, frequency and amplitude information is extracted using a multiple-pole active filter/amplifier, producing the output ring tone signal.The LT1684 uses its own ring tone output as a reference for generating local supply rails using complementary high voltage external MOSFETs as dynamic level-shifting devices. This 'active tracking' supply mode of operation allows linear generation of the high voltage ring tone signal, reducing the need for large high voltage filtering elements.

The LT®3761 is a DC/DC controller designed to operate as a constant-current source and constant-voltage regulator. It features a programmable internal PWM dimming signal. The LT3761 is ideally suited for driving high current LEDs, but also has features to make it suitable for charging batteries and supercapacitors. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A voltage feedback pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant-voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize efficiency, performance or external component size. The LT3761 senses output current at the high side or at the low side of the load. The PWM input can be configured to self-oscillate at fixed frequency with duty ratio programmable from 4% to 96%. When driven by an external signal, the PWM input provides LED dimming ratios of up to 3000:1. The CTRL input provides additional analog dimming capability.

The LT8500 is a pulse width modulation (PWM) generator with 48 independent channels. Each channel has an individually adjustable 12-bit (4096-step) PWM register and a 6-bit (64-step) ±50% correction register. All controls are programmable via a simple serial data interface. Three banks of 16-channels each can be configured such that they operate 120° out-of-phase with each other. The LT8500 features two diagnostic information flags: synchronization error and open LED. The flags are sent, with additional state information, on the serial data interface during status read back. The 50MHz cascadable serial data interface includes buffering and skew-balancing, making the chip suitable for PWM intensive applications such as large screen LCD dynamic backlighting and mono-, multi- and full-color LED displays. The LT8500 is also ideally suited to control three LT3595A LED drivers.

The LTC3035 is a micropower, VLDO (very low dropout) linear regulator which operates from input voltages as low as 1.7V. The device is capable of supplying 300mA of output current with a typical dropout voltage of only 45mV. To allow operation at low input voltages the LTC3035 includes a charge pump generator that provides the necessary bias voltage for the internal LDO circuitry. Output current comes directly from the input supply for high efficiency regulation. The charge pump bias generator requires only a 0.1ΜF flying capacitor and a 1ΜF bypass capacitor for operation. The low 0.4V internal reference voltage allows the LTC3035 to be programmed to much lower output voltages than commonly available in LDOs. The output voltage is programmed via two tiny SMD resistors. The LTC3035's low quiescent current makes it an ideal choice for use in battery-powered systems. Other features include high output voltage accuracy, excellent transient response, stability with ultralow ESR ceramic capacitors as small as 1ΜF, short-circuit and thermal overload protection, output current limiting and reverse output current protection. The LTC3035 is available in a tiny, low profile (3mm × 2mm × 0.75mm) 8-lead DFN package.

The LTC®6993 is a monostable multivibrator (also known as a "one-shot" pulse generator) with a programmable pulse width of 1Μs to 33.6 seconds. The LTC6993 is part of the TimerBlox® family of versatile silicon timing devices. A single resistor, RSET, programs an internal master oscillator frequency, setting the LTC6993's time base. The output pulse width is determined by this master oscillator and an internal clock divider, NDIV, programmable to eight settings from 1 to 221.