Seiko Instruments introduces the S-818 Series of extremely low quiescent current low-dropout (LDO) voltage regulators. Packaged in the miniature SOT-23-5 or SOT-89-5 casings, the S-818 is a positive LDO voltage regulator developed utilizing CMOS technology. The low power consumption and high-output current allow the S-818 to be used in a wide range of applications, such as cellular phones, PDAs, MP3 players, notebook PCs, hand-held games, home security, digital cameras and portable audio devices.

The S-818 features a low quiescent current of 100 nA typical, 500 nA maximum with the power off and 30 A typical, 40 A maximum during operation. Additional features include a low drop-out voltage of 170 mV typical, a high output current of 200 mA for the 3 V version and 300 mA for the 5 V version; and a high-precision output voltage ranging from 2 to 6 V.

The S-818 has a built-in power-off circuit, which ensures long battery life, and a built-in low on-resistance transistor provides low dropout voltage and large output current.

The data sheet for the S-818 can be found at: www.seiko-usa-ecd.com/intcir/html/power/s818.html

Seiko Instruments USA Inc., 2990 West Lomita Blvd., Torrance, CA 90505. Phone: 800-934-9334; Fax: 909-975-5699.

The S-818 Series is a positive voltage regulator developed using CMOS technology and features low dropout voltage, high output voltage accuracy and low current consumption. A built-in low on-resistance transistor provides low dropout voltage and large output current. A ceramic capacitor of 2 ýF or more can be used as an output capacitor. A power-off circuit helps ensure long battery life.

The SOT-23-5 miniaturized package and the SOT-89-5 package are recommended for configuring portable devices and large output current applications, respectively.

Some applications include a power source for battery-powered devices personal communication devices, and for home electric/electronic appliances.

The regulator uses an error amplifier to compare a reference voltage with part of the output voltage divided by the feedback resistors. It supplies the output transistor with the gate voltage, necessary to ensure an output voltage free of fluctuations caused by input voltage and temperature. The S-818 Series uses a low on-resistance Pchannel MOSFET as the output transistor. Designers should ensure that voltage-out does not exceed voltage-in +0.3 V to prevent the voltage regulator from breaking down. This can cause an inverse current to flow from the voltage-out pin to the voltage-in pin through the parasitic diode.

The power-off pin activates and inactivates the regulator. When the on/off pin is switched to the power off level, the operation of all internal circuits stop. Current consumption is suppressed when the built-in Pchannel MOSFET output transistor between the voltage in and voltage out pin is switched off. Since the on/off pin is neither pulled down nor pulled up internally, it is recommended that the circuit should not be kept in the floating state.

The S-818 series needs an output capacitor between the voltage-out pin and ground pin for phase compensation. A small ceramic or electrolytic capacitor of 2 mF or more can be used. If a tantalum or an aluminum electrolytic capacitor is used, its capacitance must be 2 mF or more and the equivalent series resistance (ESR) must be 10 ohms or less. When using an aluminum electrolytic capacitor be aware of oscillation due to an increase of ESR at low temperatures. Evaluate the performance including temperature characteristics before prototyping the circuit. Overshoot and undershoot characteristics differ depending upon the type of the output capacitor. The voltage regulator may oscillate when the impedance of the power supply is high and the input capacitor is small.

Pricing begins at $0.45 in quantities of 3000 for the SOT-23-5 packaging and $0.45 each in quantities of 1000 for the SOT-89-5 packaging. The S-818 is available now through a national network of authorized distributors, including All American, Mouser and Future Electronics