Ultra Low Power Consumption 150 mV dropout voltage 25 �A ground current 150 mA Enable/Shutdown Control SOT23-5 package Thermal limiting 300 mA peak current

wide variety of external capacitors, and the compact SOT23-5 surface-mount package. The FAN2502/03 family of products offer significant improvements over older BiCMOS designs and are pin-compatible with many popular devices. The output is thermally protected against overload. The FAN2502 and FAN2503 devices are distinguished by the assignment of pin 4: FAN2502: pin 4 � ADJ, allowing the user to adjust the output voltage over a wide range using an external voltage divider. FAN2502-XX: pin 4 � BYP, to which a bypass capacitor may be connected for optimal noise performance. Output voltage is fixed, indicated by the suffix XX. FAN2503-XX: pin 4 � ERR, a flag which indicates that the output voltage has dropped below the specified minimum due to a fault condition. The standard fixed output voltages available are 2.85V, 3.0V, and 3.3V. Custom output voltage are also available: please contact your local Fairchild Sales Office for information.

Cellular Phones and accessories PDAs Portable cameras and video recorders Laptop, notebook and palmtop computers

The FAN2502/03 family of micropower low-dropout voltage regulators utilize CMOS technology to offer a new level of cost-effective performance in GSM and TDMA cellular handsets, Laptop and Notebook portable computers, and other portable devices. Features include extremely low power consumption and low shutdown current, low dropout voltage, exceptional loop stability able to accommodate a

EN VIN Bandgap Error Amplifier p VOUT ADJ Thermal Sense FAN2502 GND FAN2502-XX EN VIN Bandgap p VOUT ERR Error Amplifier Thermal Sense VIN Bandgap p VOUT EN BYP Error Amplifier

Pin Name ADJ BYP ERR Pin No. 4 Type Input Passive Open drain Pin Function Description FAN2502 Adjust. Ratio of potential divider from VOUT to ADJ determines output voltage. FAN2502-XX Bypass. Connect 470 pF capacitor for noise reduction. FAN2503-XX Error. Error flag output. 0: Output voltage 95% of nominal. 1: Output voltage 95% of nominal. Enable. 0: Shutdown VOUT. 1: Enable VOUT. Voltage Input. Supply voltage input. Voltage Output. Regulated output voltage. Ground.

Designed utilizing CMOS process technology, the FAN2502/03 family of products are carefully optimized for use in compact battery-powered devices, offering a unique combination of low power consumption, extremely low dropout voltages, high tolerance for a variety of output capacitors, and the ability to disable the output to less than 1�A under user control. In the circuit, a difference amplifier controls the current through a series-pass P-Channel MOSFET, comparing the load voltage at the output with an onboard low-drift bandgap reference. The series resistance of the pass P-Channel MOSFET is approximately 1, resulting in an unusually low dropout voltage under load when compared to older bipolar pass-transistor designs. Protection circuitry is provided onboard for overload conditions. In conditions where the device reaches temperatures exceeding the specified maximums, an onboard circuit shuts down the output, where it remains suspended until it has cooled before re-enabling. The user is also free to shut down the device using the Enable control pin at any time. Careful design of the output regulator amplifier assures loop stability over a wide range of ESR values in the external output capacitor. A wide range of values and types can be accomodated, allowing the user to select a capacitor meeting his space, cost, and performance requirements, and enjoy reliable operation over temperature, load, and tolerance variations.

Depending on the model selected, a number of control and status functions are available to enhance the operation of the LDO regulator. An Enable pin, available on all devices, allows the user to shut down the regulator output to conserve power, reducing supply current to less than 1�A. The adjustable-voltage versions of the device utilize pin 4 to connect to an external voltage divider which feeds back to the regulator error amplifier, thereby setting the voltage as desired. Two other functions are available at pin 4 in the fixed-voltage versions: in noise-sensitive applications, an external Bypass capacitor connection is provided that allows the user to achieve optimal noise performance at the output, while the Error output functions as a diagnostic flag to indicate that the output voltage has dropped more than 5% below the nominal fixed voltage.

In the fixed-voltage configuration, connecting a capacitor between the bypass pin and ground can significantly reduce noise on the output. Values ranging from to 10nF can be used, depending on the sensitivity to output noise in the application. At the high-impedance Bypass pin, care must be taken in the circuit layout to minimize noise pickup, and capacitors must be selected to minimize current loading (leakage). Noise pickup from external sources can be considerable. Leakage currents into the Bypass pin will directly affect regulator accuracy and should be kept as low as possible; thus, highquality ceramic and film types are recommended for their low leakage characteristics. Cost-sensitive applications not concerned with noise can omit this capacitor.

The FAN2502/03 allows the user to utilize a wide variety of capacitors compared to other LDO products. An innovative design approach offers significantly reduced sensitivity to ESR (Effective Series Resistance), which degrades regulator loop stability in older designs. While the improvements featured in the FAN2502/03 family greatly simplify the design task, capacitor quality still must be considered if the designer is to achieve optimal circuit performance. In general, ceramic capacitors offer superior ESR performance, at a lower cost and a smaller case size than tantalums. Those with or Y5Vdielectric offer the best temperature coefficient characteristics. The combination of tolerance and variation over temperature in some capacitor types can result in significant variations, resulting in unstable performance over rated conditions. Enable Pin Applying a voltage 0.4V or less at the Enable pin will disable the output, reducing the quiescent output current to less than 1�A, while a voltage 2.0V or greater will enable the device. If this shutdown function is not needed, the pin can simply be connected to the VIN pin. Allowing this pin to float will cause erratic operation. Error Flag (FAN2503 only) To indicate conditions such as input voltage dropout (low VIN), overheating, or overloading (excessive output current), the ERR pin indicates a fault condition. is an opendrain output which is HIGH when the voltage at VOUT is greater than 95% of the nominal rated output voltage and LOW when VOUT is less than 95% or the rated output voltage, as specified in the error trip level characteristics. A logic pullup resistor 100K is recommended at this output. The pin can be left disconnected if unused. Thermal Protection The FAN2502/03 is designed to supply high peak output currents to 1A for brief periods, however this output load will cause the device temperature to increase and exceed maximum ratings due to power dissipation. During output overload conditions, when the die temperature exceeds the shutdown limit temperature of 150�C, onboard thermal protection will disable the output until the temperature drops below this limit, at which point the output is then re-enabled. During a thermal shutdown situation the user may assert the power-down function at the Enable pin, reducing power consumption to the minimum level IGND x VIN.

An input capacitor of 2.2�F (nominal value) or greater, connected between the Input pin and Ground, located in close proximity to the device, will improve transient response and noise rejection. Higher values will offer superior input ripple rejection and transient response. An input capacitor is recommended when the input source, either a battery or a regulated AC voltage, is located far from the device. Any good quality ceramic, tantalum, or metal film capacitor will give acceptable performance, however tantalum capacitors with a surge current rating appropriate to the application must be selected to avoid catastrophic failure.

An output capacitor is required to maintain regulator loop stability. Unlike many other LDO regulators, the FAN2502/ 03 family of products are nearly insensitve to output capacitor ESR. Stable operation will be achieved with a wide variety of capacitors with ESR values ranging from 10 or more. Tantalum or aluminum electrolytic, or multilayer ceramic types can all be used. A nominal value of at least 1�F is recommended.