feature

Ultra Low Power 100mA at 100mV Voltage Drop Output Voltage 3.3V 100mA at 25μA Ground Current Enable/Disable Control SOT33-5 Package Thermal Limit 300mA Peak Current

application

Cell Phones and Accessories Camcorders and Video Recorders Laptops, Notebooks and Palmtops

illustrate

The FAN2510 micropower low dropout regulator utilizes CMOS technology in cell phones, notebooks and notebooks and other portable computer equipment. Features include very low power dissipation, low off current, low voltage drop, excellent loop stability, the ability to accommodate a wide variety of external capacitors and a compact SOT2 3-5 surfacemount package. FAN2510 provides mobile phone applications. These products offer significant improvements over older BiCMOS designs and are pin compatible with many popular devices. The output is thermally protected against overload. Pin 4 allows the user to use an external voltage divider over a wide range.

Absolute Maximum Ratings (1) Stresses in excess of the Absolute Maximum Ratings may damage the device. The unit may not be operational or operable under the recommended operating conditions and it is not recommended to stress parts to these levels. Additionally, prolonged exposure to stresses higher than recommended operating conditions may affect device reliability. These absolute maximum ratings are for stress ratings only.

notes:

1. Functional operation under any of these conditions is not implied. Performance and reliability are only guaranteed if recommended operating conditions are not exceeded.

2. The applied voltage must be limited within the specified range.

3. Based on thermal limit junction temperature:

4. Using Mil Standard 883E, Method 3015.7, Human Body Model 4 kV minimum. Machine model at least 400 VJEDEC Method A115-A. Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions under which actual equipment operates. Recommended operating conditions are specified to ensure optimum performance to data sheet specifications. Fairchild does not recommend exceeding or designing in the Absolute Maximum Ratings.

Functional Description: Designed in CMOS process technology, the FAN2510 has been carefully optimized for use in small battery powered devices. It offers a unique combination of low power consumption, extremely low voltage drop, high tolerance to various output capacitors, and the ability to disable outputs less than 1µA in user state control. In the circuit, the differential amplifier controls the current through the series P-channel MOSFET and compares the output to the on-board load voltage with a low-drift bandgap reference. The series resistor bypasses the P-channel MOSFET by about 1µm, resulting in an unusually low voltage drop under load compared to older bipolar transistor designs. There is an overload protection circuit on board. An on-board circuit shuts down if the device temperature exceeds the specified maximum value. output, it will hang until it cools down before re-enabling. Users can turn off devices that use the enable control pins at any time. Carefully designed output conditioning amplifiers guarantee loop stability over a wide range of ESR values with external output capacitors. A wide range of values and types can be accommodated, allowing users to select capacitors meeting (if space, cost and performance) requirements while operating reliably over temperature, load and tolerance variations. An enable pin allows the user to turn off the regulator output to save power, reducing supply current to less than 1µA. It can then be applied in 500µs, meeting the fast power cycling demands of mobile devices.

The adjustable voltage version utilizes pin 4 to connect to an external voltage divider back to the regulator error amplifier to set the desired voltage. Application Information External Capacitors - Selection Compared to other LDO products, the FAN2510 supports a variety of capacitors. Innovative Design This approach significantly reduces sensitivity to ESR (equivalent series resistance), which degrades the stability of the regulator loop in older designs. While the improvements have greatly simplified the design task, the quality of the capacitors must still be considered if the designer is to achieve optimum circuit performance. Generally speaking, ceramic capacitors come in lower cost and smaller boxes than tantalum. With X7R or Y5V dielectrics have the best temperature coefficient characteristics. Combination of Tolerance and Variation Excessive temperature of some capacitor types can cause significant variation, resulting in unstable performance beyond rated conditions.

Input Capacitor 2.2µF (nominal) or larger input capacitor, connected between the input pin and ground, located close to the device to improve transient response and noise rejection. Higher values provide better input ripple rejection and transient response. One when the input source, battery or regulated AC voltage is located remotely from the device. Any good quality ceramic, tantalum, or metal film capacitor has acceptable performance; however, tantalum capacitors with inrush current ratings must choose options appropriate to the application to avoid catastrophic failure. Output Capacitor An output capacitor is required to keep the regulator loop stable. Unlike many other LDC regulators, the FAN2510 is virtually insensitive to output capacitor ESR. Stable operation is achieved with a variety of capacitors with ESR values between 10 mΩ and 10Ω or more.

Tantalum or aluminum electrolytic, or multilayer ceramic types can be used. A nominal value of at least 1 µF is recommended. Control Function Enable Pin Applying 0.4V or less to the Enable pin will disable the output, thereby reducing the quiescent output current to less than 1µA; a voltage of 2.0V or higher enables the device. This pin can be connected to the VIN pin if the shutdown function is not required. Allowing this pin to float can result in unstable operation. Thermal protection The FAN2510 provides up to 1 A for short periods; however, this output load will cause the device temperature to increase and exceed the maximum rating due to power dissipation. When the die temperature exceeds the shutdown limit of 150°C during output, the onboard thermal protection disables the output until the temperature falls below this limit; at this point, the output will be re-enabled. In thermal shutdown conditions, the user may assert a power-down feature at the enable pin, reducing power consumption to a minimum level.

Thermal Characteristics The FAN2510 provides 100 mA operating at the specified output for mode (junction) temperatures up to 125°C. Once power dissipation and thermal resistance are known, the maximum junction temperature can be calculated for the device. Thermal resistance when calculating power dissipation from known electrical parameters is a result of the thermal characteristics of the compact SOT2 3-5 surface mount package and surrounding PC board mounting. Power dissipation is equal to the input to output voltage drop and output current plus ground current multiplied by the input voltage, or:

The ground pin current, IGND, can be found in the diagram provided in the Electrical Characteristics section. The relational wrapper describing thermal behavior is:

where TJ(max) is the maximum allowable junction temperature of the die, which is 125°C, and TA is the ambient. Operating temperature. θJA depends on the surrounding PC board layout and can be obtained empirically. While the θJC (junction-to-case)-5 package of the SOT23 is specified at 130°C/W, the θJA of the smallest PCB package is at least 235°C/W. This can be improved PCB grounding by providing heat sinks around copper. Depending on the copper size area, the resulting Th JA can range from approximately 180°C/W per square inch to nearly 130°C/W square inch. The addition of vias, stiffeners, and other reinforcements to the backside copper can reduce this value. The heat generated by the cooling of other nearby equipment must be included in the design. Once the limiting parameters in these two relationships have been determined, the design can be modified to ensure that the equipment remains within the specified operating conditions. If overload conditions are not considered, equipment may enter a thermal loop, where the circuit goes off, cools, turns back on, then overheats and shuts down again due to an unmanaged fault condition.

Adjustable Version Operation The adjustable version of the Fan 2500 includes an input that allows the user to select the output voltage pin to adjust from 1.8 volts to close to the VIN, using an external resistor separator. The voltage VADJ supplied to the ADJ pin is equal to the on-board bandgap reference voltage of 1.32 V (typ) before it is fed to the on-board error amplifier VADJ that adjusts the output. The formula is as follows:

The total value of the resistor chain should not exceed a total of 250 kΩ to maintain the error amplifier bias under no-load conditions. Programming the output voltage 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 generate bias current error calculations. General PCB Layout Considerations For optimum device performance, attention must be paid to circuit layout and grounding techniques. Establish a small local ground, connect the ground pin output and bypass capacitors, it is recommended that the input capacitors be grounded to the main ground plane. The quiet place is to use feed-back vias to the main ground plane. In general, high-frequency compensation components (input, bypass, and output capacitors) should be placed as close to the device as possible. Proximity is especially important for the realization of the output capacitors for the optimal noise compensation amplifier for onboard errors, especially under high load conditions. Large local ground copper areas provide heat dissipation when high power dissipation significantly increases device temperature, discussed above. Component side copper wire provides better thermal performance of this surface mount device, compared to only the underside.