TechBites Says:
Between their new Ecospeed family of DC-DC-converters and the smart lighting wireless transceivers they recently introduced, it’s apparent that Semtech has decided to turn its formidable analog design talents towards the green power market in a big way. The SC173/174 Eco-Speed controllers announced here feature high efficiency and integrated FETs that supply up to 4 A for point-of-load applications. The SC 493 which was also recently released, has high voltage capability (up to 28V) for so-called digital power applications. All these devices feature a so-called Adaptive On-Time (AOT) Architecture that delivers high efficiency across a very wide load range and very quick transient response that makes them an excellent candidate for many industrial, networking/comms, and office automation applications. Of course it doesn’t hurt that these highly-integrated devices eliminate the need for external compensation components, a feature that will give you a more compact, reliable, and lower-cost design.
Semtech’s AOT architecture is derived from hysteretic architectures which use a comparator instead of a traditional error amplifier to turn the converter on and off. Like the standard hysteretic approach it simplifies the external compensation loop but it also avoids some of the problems associated with these kinds of designs. Instead of using a simple fixed comparator, the EcoSpeed devices have a variable control loop that dynamically adjusts the on-time based on input and output voltages on a cycle-by-cycle basis. Semtech says that this allows the controller to operate in a pseudo-fixed frequency mode. Keeping the switching frequency variations within 15% of its nominal frequency results in very predictable EMI characteristics which make filtering and other suppression techniques much easier (and cheaper) to implement. EcoSpeed controllers minimize audible noise by keeping their switching frequency at 25 kHz or above – even in standby mode. The controller can also be programmed to keep its oscillator above a particular critical frequency by pulling down one of its control input lines using a low-power resistor.
In addition to all the energy-saving features they’ve managed to cram into their EcoSpeed switches, Semtech has also paid close attention to making their parts easy and inexpensive to use. For example, the converter’s drive and filer elements are designed to work well with the higher equivalent series resistance (ESR) found in ceramic. Because the device works equally well with ceramic or electrolytic input/output capacitors engineers have more design flexibility that can help them trim their BOM costs
The other major contributor to the EcoSpeed converters’ light-load efficiency is their SmartDrive two-step, high-side FET turn-on scheme which provides precise control of the gate current injection into their integrated low Rdson power FETs. Providing a two-stage turn-on signal for every cycle limits gate current inrush spike during initial conduction period also significantly reduces the level of EMI the produced by the switch.
The SC493, which I mentioned earlier, has a 28V working voltage and shares the same AOT regulator architecture but also has a lot more programmable features which can be accessed via its I2C interface. This allows an MCU or other host controller to set most of the the converter’s operating parameters, including VOUT offset & margining, operating frequency, power-on delay, soft-start timing, and more. The digital control also enables digital monitoring of virtually every analog and digital parameter within the chip. Besides making it a snap to create a digitally-controlled "smart" power supply, Semtech says that this high level of programmability makes it possible for your product to perform voltage margining self-tests during manufacturer to do accelerated burn-in and weed out potential field failures.
The SC173 and SC174 are available immediately in production quantities and are priced at $1.80 for the SC173 and $1.90 for the SC174 each in 3,000-piece lots. Ordering codes are SC174MLTRT and SC173MLTRT. Evaluation boards (SC174EVB and SC173EVB) are also available. Semtech offers comprehensive design assistance, including field- and factory-based support
The 28V-capable SC493 (announced June 16) is available immediately in production quantities and is priced at $1.06 each in 3,000-piece lots. The ordering code is SC493ULTRT.
For more information on the SC173, click here.
For more information on the SC174, click here.
For more information on other products in the EcoSpeed family of DC-DC converters, click here.
Data sheets, volume pricing, and delivery quotes, as well as evaluation kits and samples, are available at www.semtech.com/info.
Semtech Says:
SC173 (3A) and SC174 (4A) point-of-load regulators are optimized for demanding “green” applications
Semtech Corp has launched the SC173 and SC174 buck regulators. These devices are the latest in the company’s EcoSpeed DC-DC converter platform, which incorporates Semtech’s advanced, patent-pending adaptive on-time architecture to achieve best-in-class performance in next-generation dynamic point-of-load (POL) applications. They are ideal for office automation, networking and communications equipment; set-top boxes; portable products; power supply modules; and other embedded products. The new SC173 and SC174 POL regulators help designers meet today’s demanding green power requirements by efficiently managing both standby and full current demands.
The SC173 and SC174 converters use Semtech’s EcoSpeed architecture to achieve the best of conventional current mode, voltage mode and constant on-time control topologies, with minimal tradeoffs. This architecture enables ultra-fast transient response and very high efficiency across light to full power loads, while eliminating the need for external compensation components, providing a simple, space-saving and cost-effective power management solution.
The EcoSpeed architecture uses an advanced control loop to dynamically adjust the on-time based on input voltage and output voltage. This approach enables a pseudo-fixed frequency operation with ±15% accuracy and very predictable EMI -- comparable to conventional voltage mode and current mode topologies, and better than constant on-time and hysteretic architectures where frequencies are unpredictable.
The SC173 and SC174 EcoSpeed converters are programmable from 200kHz to 1MHz allowing designers to optimize their power supply to maximize either the conversion efficiency or the solution size. They also incorporate Semtech’s proprietary SmartDrive™ technology, which is a two-step, high-side FET turn-on technology designed to reduce EMI in noise-sensitive applications.
Very low power during standby mode is increasingly important to comply with emerging “green” initiatives. However, most electronic products also require fast “wake-up” capability, which demands fast recovery from low-power standby to full-power steady state mode. The SC173 and SC174 EcoSpeed converters solve this challenge with an ultrasonic power-save (UPSAVE) mode. UPSAVE lowers the switching frequency to cater to low-power standby requirements, thereby by reducing the switching losses associated with the power FET gate charge. This results in up to 95% peak standby efficiency. Then, when the load changes from standby to steady state, the EcoSpeed technology cycle-by-cycle response quickly exits UPSAVE mode providing very fast power-up response time. Additionally, UPSAVE ensures that the device switching frequency stays above the 25kHz threshold, thereby eliminating audible resonance.
The EcoSpeed architecture allows the SC173 and SC174 to work with ceramic input and output capacitors, providing design flexibility and reliability. This, combined with no external compensation components optimizes BOM costs and reduces customers’ time-to-design. The SC173 and SC174 offer output currents of 3A and 4A respectively and are packaged in a 10-pad, 3.0 x 3.0 x 1.0 mm, lead-free, halogen-free MLPD package for further space savings.
“Achieving power efficiency during standby mode, while providing ‘instant-on’ and high operating efficiency presents a tremendous challenge in meeting today’s green power initiatives,” said Alan Burchfield, Senior Product Marketing Manager for Semtech’s Power Management Group. “Our EcoSpeed DC-DC converters help designers easily and cost-effectively solve these issues. The EcoSpeed platform represents the next step in our commitment to delivering unmatched power management solutions for emerging green electronic product requirements.”
Key Features of the SC174 and SC173 EcoSpeed DC-DC Converters
- Ultra-fast transient response
- Very high efficiency across light to full power loads
- No external compensation components required
- Ultrasonic PSAVE: up to 95% peak efficiency during light loads
- Pseudo-fixed switching frequency with ±15% accuracy (programmable 200kHz to 1MHz)
- SmartDrive™ technology reduces EMI
- VIN: 3V to 5.5V; IOUT: 3A (SC173) & 4A (SC174)
- Fully protected with output OVP, UVP and short circuit protection
- 10-pad MLPD package – 3.0 x 3.0 x 1.0 mm
The SC173 and SC174 join Semtech’s existing family of higher voltage, higher current EcoSpeed DC-DC converters, providing the same adaptive on-time architecture benefits for lower voltage, lower current point-of-load applications. Additional devices in the family include ultrasonic power-save devices: SC414 (6A), SC417 (10A), SC418 (30A controller with low dropout regulator), SC419 (30A controller); as well as standard power-save devices: SC424 (6A) and SC427 (10A).
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