Electronic Design


Full-Bridge PWM Motor Driver Features Low Power Dissipation
Allegro MicroSystems Inc.
(508) 853-5000; fax (508) 853-5049; www.allegromicro.com

The A3959 is a pulse-width-modulated (PWM) current-controlled single full-bridge motor driver integrated circuit based on DMOS technology. It offers low RDS(ON) as well as synchronous rectification. In addition to the company's patented mixed-decay PWM current control, this device features high peak currents and fast switching speeds.

This motor driver is designed for PWM current control of dc motors. It is capable of output currents to ±3 A and operating voltages to 50 V. Internal, fixed, off-time PWM control can be set to operate in either slow, fast, or mixed-decay mode. The mixed-decay mode reduces the high ripple-current effects of fast decay and minimizes the limited bandwidth issues of slow decay. It also adjusts the percent of off-time spent in each mode through the use of a unique percent-fast-decay pin (PFD). PHASE and ENABLE input terminals are provided for use in controlling the speed, torque, and direction of a dc motor.

The A3959 is available in a 24-lead plastic DIP and a 24-lead plastic SOIC. Available now, the motor driver costs $2.27 per part in 1000-unit quantities.

Inverting Switching Regulator Suits Next-Generation Hard-Disk Drives
National Semiconductor
(800) 272-9959; www.national.com

The LM2611 is a small, low-noise MR preamplifier power solution for next-generation hard-disk drives. This pulse-width-modulation (PWM) inverting switching regulator is capable of supplying −5 V at 300 mA from a 5-V input. It delivers the power required by present and future hard-disk drive (HDD) designs as well as other voltage-inverter requirements. Its 1.4-MHz oscillator enables the use of smaller external components.

The Cuk topology reduces peak current as well as the external component count. The LM2611 operates from inputs ranging from 2.7 to 14 V. It is capable of producing a negative output voltage of up to −36 V. With a low 0.5-Ω switch, the device achieves higher efficiency. Additional features include internal compensation, cycle-by-cycle current limit, and low noise. The LM2611 is also suited for creating the negative bias required by active matrix displays or CCDs in digital cameras. Additionally, the device can create the −5 V required by tuners in set-top boxes and cable modems. The device is available in two grades. While the A-grade features a higher current limit of 1.2 A, the B-grade features a current limit of 0.9 A.

The A-grade version and B-grade version cost $1.28 and $1.10 each, respectively. All pricing is for 1000-unit quantities.

TAGS: Components
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