Electronic Design

Power Advances Target Multiple Markets

Claimed as a first in the industry, Microchip has developed an op amp that includes mCal—an on-chip calibration circuit that calibrates offset voltages at power up using an internal power-on reset detector, or based upon the state of an external pin. The result, says the company, is a low initial voltage offset and a means to minimise drift over time and temperature. Such features will target the op amp for applications involving instrumentation and sensor conditioning.

The high-bandwidth, low-power MCP651/2/5 (MCP65x) op amps provide low bias and quiescent currents, high-output drive capability, and a rail-to-rail output for better performance across the entire operating-voltage range (Fig. 1). A frequency bandwidth of 50MHz and a rail-to-rail output drive current of up to 95mA suit the MCP65x for demanding applications in consumer, industrial, and medical markets.

The high-output drive current, which enables the MCP65x to drive heavy loads, also results in improved performance across a wide range of applications. In addition, the rail-to-rail output provides greater dynamic range—even at lower operating voltages—for more accurate performance across the operating voltage range.

Electrostatic discharge (ESD) protection now comes in a minuscule 4 x 4mm QFN package. Intersil’s series of small-footprint, quad 16.5kV ESD-protected RS-422 transmitters are designed for motorcontrol applications, process control networks, telecommunications products, and factory automation systems (Fig. 2). The transmitters are designated ISL32179E, ISL32272E, and ISL32274E.

The devices can withstand ESD during assembly and while in use, featuring ±16.5kV ESD protection that meets HBM and IEC61000-4-2 standards on transmitter outputs. All of the transmitters also have power-saving low-output leakage currents at just ±20μA. Designed to operate from either 3.3V or 5V and at temperatures between -40°C to 125°C, the new transmitters can replace existing RS-422 transmitters that are restricted to 5V supply voltages or operate in limited temperature ranges.

The ISL32179E, ISL32272E, and ISL32274E suit designs using the RS-422 communication interface.

Data rates reach 32Mbits/s, and quiescent current is 0.8mA, maximum. Slew-rate-limited versions are also offered, so low-data-rate applications can minimise EMI and transmission- line reflections. Shutdown supply current is as low as 60μA on the QFN package versions. Driver (Tx) outputs are tri-statable and incorporate a hot-plug feature to keep them disabled during powerup and power-down.

Industry-standard versions are available in TSSOP or NSOIC packages, while the ISL32179E comes in tiny 4 x 4mm QFN packages, which are 50% smaller than the TSSOPs. The ISL32179E also features data-rate and enable options, offering maximum design versatility. Multiple enable pins allow users to choose active high or low group enables, paired-enables (EN12 and EN34) or individual channel enables, available on the ISL32179E. Furthermore, with the ISL32179E only, speed select pins make it possible for users to select data rates from 460kbps to 32Mbps.

Moving onto a new development in the brick business, Vicor just recently added eight wide-input Micro dc-dc converters to its 28Vdc input family (Fig. 3). These models have nominal output voltages ranging from 3.3 to 48Vdc, and a maximum power of 100W (50W at 3.3 and 5VOUT, and 100W at 12, 15, 24, 28, 36 and 48VOUT).

These modules target either 12V or 24V applications, such as MILCOTS or commercial battery systems in vehicles. They also meet the European standard for electronic equipment used in railway rolling stock (EN50155), and can be used in various vehicle or man-portable applications including lighting, communications, portable test equipment, display, and control systems.

With efficiency up to 82%, the converters operate from 28V nominal input with an input range of 9 to 36V. These models come in four environmental grades (operating temps as low as -55°C) and offer six pin and three baseplate options.

These compact modules also come in RoHS-compliant variants. They measure 57.9 x 36.8 x 12.7mm (2.28 x 1.45 x 0.5in), with a trim range of 10% to 110% of nominal output voltage.

Improved switching performance for synchronous buck converter and battery protection is behind the release of International Rectifier’s latest series of 25V and 30V N-channel trench HEXFET power MOSFETs (Fig. 4).

The MOSFETs also are available in a Power QFN package to deliver greater power density, when compared with an SO-8 package. Yet, still, they are able to keep the identical pin-out configuration. Depending on the application, the dual SO-8 MOSFETs enable a “two for one” exchange to reduce the component count.

Single and dual N-channel MOSFETs are available. Single devices are offered in a PQFN 5x6mm and 3x3mm package optimised for high volume production in addition to D-PAK, I-PAK and SO-8 packages while dual devices are offered in an SO-8 package. The new devices can be offered as halogen-free.

Not to be outdone, Linear Technology Corp. recently developed the LT3650-4.1 and LT3650- 4.2. These are compact, monolithic high-voltage battery chargers targeted for single-cell Li-ion/polymer batteries (Fig. 5).

Linear Technology says that the device’s switch-mode architecture minimises power dissipation without compromising board space. The LT3650-4.1/4.2 operates from 4.75V to 32V. In addition, it features a 40V absolute maximum rating for extended system margin. User-selectable timer or C/10 termination doesn’t require an external microcontroller, thus simplifying the design.

Charge current is programmable and dynamically adjustable up to 2A; the power device is integrated on the chip to save board space. The LT3650-4.1/4.2 doesn’t require external high-precision resistors to set the float voltage, which further saves on both cost and space.

Potential applications include industrial handheld instruments, 12V to 24V automotive and heavy equipment, desktop cradle chargers, and small notebook or tablet computers. The LT3650-4.1 provides a 4.1V battery float voltage, which allows for high-temperature safety margin. Meanwhile, the LT3650-4.2 features a 4.2V final charge voltage for optimised battery run time.

The LT3650-4.1/4.2’s 1MHz operating frequency and currentmode architecture make it possible to use small inductors and capacitors. This ultimately will minimise noise and filtering needs. Final float voltage accuracy is specified at ±0.5%, charge current accuracy is ±5%, and C/10 detection accuracy is ±2.5%.

Once charging is terminated, the LT3650-4.1/4.2 chargers will automatically enter a low-current standby mode that diminishes the input supply current to 85μA. In shutdown, the input bias current is reduced to 15μA. The LT3650- 4.1/4.2 maximises battery life during all of the non-charging periods, draining less than 1μA from the battery.

TAGS: Microchip
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