Tucson, Ariz. Apex Microtechnology Corp. has been known for high-power, high-slew-rate devices that are hard to find in compact packages. With a power single-in-line package, Apex has been producing hybrid power amps capable of driving a dozen amps or more, and pushing it up the hill at 350-V/microseconds rates. Apex's newest addition is a pulse-width modulator (PWM) amplifier-an H-bridge configuration-that's designed to drive high inductive loads like motors and speaker coils. The SA60 runs from an 80-V supply and puts on 10 A continuously (up to 15 A peak).
The hybrid op amp includes a PWM oscillator, H-bridge drive circuitry and four n-channel MOSFETs in an H-bridge configuration. In motordrive applications, the analog input provides the signal for controlling motor direction and speed. In audio applications, the analog input modulates the switch-mode amplifier (and external filters are required to remove the digital artifacts from the output). The device is 97 percent efficient, said applications manager Granger Scofield.
An external capacitor can control the switching frequency of the SA60 PWM. In analog applications, like motor drive or audio, the switching frequency will range from 22 to 125 kHz (well outside the audio range). For digital applications, the switching frequency will go up to 500 kHz. For strictly digital pulse driving, a TTL-compatible signal controls polarity and another TTL input turns the device on and off.
In motor-drive applications, two current-sense pins allow amplitude and direction control, which Scofield said were useful for brush-type motors.
The 12-pin Apex power SIP package increases the current rating of the SA60 up to 2x over similar devices in TO-3 cans. The SA60 has a peak current rating of 15 A. Power dissipation for the Apex package is up to 140 W. The SA60 is priced at $90 in 100s and is available is now.
Call (520) 690-8603
Issue of January 4, 1999; EETInfo No. 606