Features: Ultra Low Power 100mA at 100mV Voltage Drop 100mA at 25μA Ground Current Enable/Disable Control SOT33-5 Package Thermal Limit 300mA Peak Current

Applications: Cell Phones and Accessories PDA Camcorders and Video Recorders Notebooks, Notebooks and Palmtops

Description: The fan2500/01 series of micro-power low-dropout regulators utilize CMOS technology to provide a new level of GSM and TDMA cellular networks cost-effective for cell phones, notebooks and other portable devices. Features include extremely low power consumption and low shutdown current, low voltage loss, excellent loop stability, the ability to accommodate a wide variety of external capacitors and compact SOT2 3-5 surface mount components. The FAN2500 /01 series offer significant improvements over older bicmos designs and are pin compatible with many popular devices. This output is thermally protected against overload. The difference between the FAN2500 and FAN2501 devices is the assignment of pin 4: FAN2500: Pin 4 – ADJ, allowing the user to adjust a wide range of output voltage separators using an external voltage. FAN2500-XX: Pin 4 – BYP, bypass capacitor can be connected for best noise performance. The output voltage is fixed and indicated by the suffix XX. FAN2501-XX: Pin 4 – err, indicates that the output voltage has dropped below the specified minimum value due to a fault condition. Standard fixed output voltages are 2.5V, 2.6V, 2.7V, 2.8V, 2.85V, 3.0V and 3.3V. Custom output voltage.

Functional Description: Designed in CMOS process technology, the FAN2500/01 series are carefully optimized for use in small battery powered devices, offering unique low power consumption, extremely low dropout voltage, high tolerance to various output capacitors, and Capable of disabling the output to less than 1 µA for user control. In the circuit, the differential amplifier controls the current mosfet through the series P channel, and the load voltage at the output is connected to the on-board low drift bandgap reference series resistor. compared to older bipolar transistor designs. There is an overload protection circuit on board. When the device reaches a temperature above the specified maximum, the on-board circuitry shuts down and reduces the output until the output cools down before re-enabling. Users are also free to turn off devices that use the enable control pins at any time. The output conditioning amplifier ensures the stability of the external output capacitor over a wide range of esr values by careful design of the loop. A range of values and types are available to allow the user to select capacitors meeting his space, cost and performance requirements, as well as reliable over temperature, overload and out of tolerance operating variations.

Depending on the model selected, there are a number of controls and status functions available to enhance the LDO regulator. There is an enable pin on all devices that allows the user to turn off the regulator output to conserve power, reducing supply current to less than 1 microamp. The adjustable voltage version of the device utilizes pin 4 to connect to an external voltage divider, which is fed back to the regulator error amplifier to set the voltage as desired. In Fixed Voltage Version: In noise sensitive applications, an external bypass capacitor connection is provided, allowing the user to obtain the best noise performance at the output, when a false output is used to indicate that the output voltage has dropped more than 5% below the rated fixed voltage. Application Information External Capacitors - Selecting the FAN2500/01 allows the user to use a variety of capacitors compared to other LDO products. Innovative design approach significantly reduces ESR (effective series resistance), reducing regulator performance loop stability in older designs. The improvements to the fan2500/01 series greatly simplify the design task, and capacitor quality must still be considered if the designer is to achieve optimum circuit performance. Generally speaking, ceramic capacitors offer superior esr performance at lower cost and smaller case than tantalum alloys. Those with X7R or Y5V dielectrics offer the best temperature coefficient characteristics. Combination of Tolerance and Variation Excessive temperature of certain capacitor types can cause significant variation, resulting in unstable performance beyond rated conditions.

Input Capacitor 2.2µf (nominal) or larger, connected between the input pin and ground, located close to the device, will improve transient response and noise rejection. Higher values will provide better input ripple rejection and transient response. Put in when the input source battery or regulated AC voltage is located away from the device. Any high-quality ceramic, tantalum, or metal film capacitor will provide acceptable performance, but tantalum capacitors have inrush current ratings suitable for the application that must be selected to avoid catastrophic failure. Output Capacitor An output capacitor is required to keep the regulator loop stable. Unlike many other LDO regulators, the FAN2500/01 series is virtually insensitive to output capacitance esr. Stable operation will be achieved with ESR values from 10MΩ to 10Ω or more. Tantalum or aluminum electrolytic, or multilayer ceramic types can be used. The nominal value of at is recommended to use at least 1 microF. Bypass Capacitor (FAN2500 Only) In fixed voltage configurations, connecting a capacitor between the bypass pin and ground can significantly reduce noise on the output. Values from 470pF to 10nF can be applied depending on the sensitivity to output noise. At high impedance bypass pins, careful circuit layout must be taken to minimize noise pickup, and capacitors must be chosen to minimize current loading (leakage). The information that noise can gain from the outside can be considerable. The current leaking into the bypass pin will directly affect the regulator accuracy and should be as low as possible; therefore, it is recommended to use high quality ceramic and thin film types with low leakage characteristics. Cost sensitive applications can ignore this capacitor due to noise concerns.

Control Functions: Enable Pin Apply 0.4V or less on the Enable pin to disable the output, reducing the quiescent output current to less than 1 microamp, while 2.0V or higher will enable the device if the shutdown function is not required Simply connecting to the VIN pin allows this pin to float and cause erratic operation. Error flags (FAN2501 only) indicate conditions such as input voltage drop (low VIN), overheating or overload (excessive output current), and error pins indicate fault conditions. It is an open-drain output and is low when the voltage is greater than 95% of the rated output voltage and when VOUT is less than 95% or the rated output voltage, as specified in the False Trip Level Characteristics. A 100KΩ logic pull-up resistor output is recommended here. You can leave the pins disconnected if not in use. The thermally protected FAN2500/01 is designed to provide up to 1A of peak output current for short periods of time, but this output load will cause the device to heat up and exceed the maximum power rating due to power dissipation. During output when the mold temperature exceeds the shutdown limit temperature of 150°C, the onboard thermal protection will disable the output until the temperature drops below this limit, the output will re-enable. In thermal shutdown conditions, the user can assert the enable pin power down function, reducing power consumption to a minimum level ignd vin

where TJ(max) is the maximum allowable junction temperature of the die at 125°C and TA is the ambient operating temperature. θja depends on the layout of the surrounding pc board and can be obtained empirically. While the θjcSOT2 3-5 package (junction box) is specified at 130°C/W, the θja for the minimum PWB footprint is a minimum of 235°C/W. This can be done by providing a heat sink around copper ground on the PWB. Depending on the size of the copper area, the resulting θja can range from about 180°C/W to one square inch to nearly 130°C/W, 4 square inches. The addition of back-band vias, stiffeners, and other enhancements can also help reduce this value by being located nearby and must be included in design considerations. Once the limiting parameters in these two relationships have been determined, the design can be modified to ensure that the device remains within specified operating conditions. If overload conditions are not considered, it is possible to enter a device into a thermal loop, where the circuit goes into a shutdown state, cools, re-enables, and then due to an uncontrolled fault condition.

Adjustable Version The adjustable version of the fan 2500/01 includes an input that allows the user to select the output voltage pin adjustment from 1.8V to close to the VIN, using an external resistor separator. The voltage VADJ supplied to the ADJ pin is fed to an on-board error amplifier that adjusts the output voltage until VADJ equals the on-board bandgap reference voltage of 1.32V (typ.) The formula is as follows: The total value of the resistor chain should not exceed a total of 250KΩ to keep the error amplifier in no-load condition. Programming the output voltage very close to the VIN requires consideration of voltage drop VDO overload, power supply and temperature variations. Note that the low-leakage fet input to the CMOS error amplifier does not result in a calculation. General PWB Layout Considerations To achieve the full performance of the device, be careful that the circuit must adhere to layout and grounding techniques. Build a small local ground, ground pin, output is recommended to connect a bypass capacitor, the input capacitor should be grounded to the main ground plane. The quiet local ground is then routed back to the main duct's ground plane using the feedthrough. In general, high frequency compensation components (input, bypass, and output capacitors) should be placed as close to the device as possible. Especially the proximity of the output capacitors. It is important from the on-board error amplifier, especially under high load conditions. A large copper area in the local area will provide the high power dissipation discussed above when the heat dissipation issues significantly raise the temperature of the device. Component-side copper traces provide better thermal performance. In contrast, the performance of such surface mount devices is only obtained when copper planes are used on the bottom.