SANTA CLARA, CALIF. National Semiconductor Corp. here and Micrel Inc. (San Jose, Calif.) have each unveiled low-dropout regulators. National is aiming its six-member LP396X family of CMOS LDO regulators at low-voltage, high-current computing applications, while Micrel has unwrapped a pair of 1-amp LDOs for converting 3.3 volts to 2.5 V and 2.5 V to 1.8 V. Micrel is putting its parts in a thermally enhanced SO-8 package that's said to be 40 percent smaller than a 1-A LDO in a traditional SOT-223.
National's devices come in 0.8-, 1.5- and 3-A output current versions with logic-controlled on/off and either an error flag (LP3961, LP3962 and LP3963) or a separate sense pin that permits remote load sensing when the regulator output pin is not next to the load (LP3964, LP3965 and LP3966). Typical dropout voltage is 240 mV at 0.8 A, 380 mV at 1.5 A and 800 mV at 3 A.
William Weiss, the power management group's product marketing manager, said the range of output currents meets the design requirements of most 5-V, 3.3-V or 2.5-V computing and networking applications. "As system manufacturers integrate low-voltage circuitry into their designs, they need regulators that can handle voltage conversion at low voltage and high current," he said.
Quiescent current is 15 microamps in shutdown mode, and the National series is said to offer low output noise as well as low output capacitor requirements (10 microfarads). Output voltage accuracy is plus/minus 1.5 percent at room temperature over load and line variations and plus/minus 3 percent over all conditions (varying load, line and temperature).
Sixteen voltage options, and an adjustable version, are possible with each product.
National's LP396X family is available in SOT-223, TO263 or TO220 packages starting at $1.01 in 1,000-piece quantities.
Lisa Wong, Micrel's product marketing engineer for LDOs, said the MIC39XXX family is designed to power 2.5-V microcontrollers, digital signal processors and programmable-logic devices from a 3.3-V ( plus/minus 10 percent) supply.
The MIC39101 is a fixed-output voltage regulator with an error flag that warns when an output is out of regulation. The MIC39102 has an adjustable-output voltage capable of going down to 1.25 V.
"With the MIC39102, users have the flexibility of tuning to any output voltage needed to optimize the performance of a microcontroller, DSP or PLD," Wong said. Dropout voltage is 410 mV at full load. Prices start at $1.50 in 100-piece quantities.
National, (800) 272-9959
EETInfo No. 604
Micrel, (408) 944-0800
EETInfo No. 605