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300mA C-MOS L.D.O. Regulator
LM1108F/SF
SOT-23
FEATURES
* Extremely Low Supply Current(50A,Typ.) * Very Low Dropout Voltage * 300mA Output Current * High Output Voltage Accuracy +/- 1.4 % * Standardor Custom Output Voltages * Over Currentand Over Temperature Protection * Small input/output differential : 0.3V for full load
SOT-23-5L (SOT-25)
APPLICATIONS
* Battery Operated Systems * Portable Computers * Portable Cameras and Video Recorders
SOT-89
* Medical Instruments * Instrumentation * Cellular/GSM/PHS Phones * Linear Post-Regulators for SMPS
* Pagers
1.Vss 2.Vin 3.Vout 4. NC 5. NC
ORDERING INFORMATION
Device Marking Package HXX LM1108 SF SOT-23 HXX LM1108 SF5 SOT-25 1108 X.X LM1108 F SOT-89 (Note : "XX" is Output Voltage for SOT-23 Pkg, 1.5V=H15, 1.8V=H18....3.3V=H33)
DESCRIPTION
The LM1108 is a fixed output,high accuracy(typically 0.5%) C MOS low drop-out regulator. Total supply current is typically 50A at full load (20 to 60 times lower than in bipolar regulators). LM1108 key features include ultra low noise operation, very low dropout voltage (typically 240mV at full load), and fast response to step changes in load. The LM1108 in corporates both over temperature and over current protection. The LM1108 is stable with an output capacitor of only1F and has a maximum out put current of 300mA. It is available in a SOT-23 & SOT-89 package
TYPICAL APPLICATION CIRCUIT
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300mA C-MOS L.D.O. Regulator
LM1108F/SF
ABSOLUTE MAXIMUM RATING (Note 1) Supply Voltage (Vin) Output Current (Iout) Output Voltage (Vout) Total Power Dissipation (Pd) SOT-89 SOT-23 Operating Ambient Temperature (Topr) Lead Temperature (soldering, 5 sec) Storage Temperature (Tstg) +6.5V 300 mA Vss-0.3 to Vin+0.3V 500 mW 230 mW -30 ~ +80 C 260C -40 ~ +125 C
ELECTRICAL CHARACTERISTICS
Note.1 : Load Regulation is measured using pulse techniques with duty cycle<5%
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300mA C-MOS L.D.O. Regulator
Detail Description
LM1108F/SF
- The LM1108 is aprecision, fixed output LDO. Un like bipolar regulators, the LM1108's supply current does not increase with load current. In addition,VOUT remains stable and with in regulation over theen tire 0mA to IOUT MAX operating load currentrange, (an important consideration in RTC and CMOS RAM battery back-up applications). Figure3-1shows a typical application circuit.
1. Output Capacitor 1uF(min) capacitor from VOUT to ground is required. The output capacitor hould have an effective series resistance greater than 0.1 and less than .0. 1uF capacitor should be connected from VIN to GND if there is more than 10 inche sofwire between the regulator and the AC filter capacitor ,or if a battery is used as the power source. Aluminum electrolytic or tantalum capacitor types can be used. (Since many aluminum electrolytic capacitors freeze at approximately -30C, solid tantalums are recommended for applications operating below -25 C.) When operating from sources other than batteries,supply-noise rejection and transient response can be improved by increasing the value of the input and output capacitors and employing passive filtering techniques. 2. THERMAL CONSIDERATIONS 2.1 Thermal Shutdown Integrated thermal protection circuitry shuts the regulator off when die temperature exceeds150C. The regulator remains off until the die temperature drops to approxi mately 140C. 2.2 Power Dissipation The amount of power the regulator dissipate is primarily a function of input and output voltage, and output current. The following equation is used to calculate worst case actual power dissipation:
EQUATION 2-1: TABLE 2-1 :
The maximum allowable power dissipation (Equation 2-2) is a function of the maximum ambient temperature(TAMAX), the maximum allowable die temperature(TJMAX) and the thermal resistance from junction-to-air(JA).
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300mA C-MOS L.D.O. Regulator
LM1108F/SF
EQUATION 2-2:
Table 2-1 shows various values of JA for the LM1108 versus board copper area. TABLE 2-1 : THERMAL RESISTANCE GUIDELINES FOR LM1108
Equation 2-1can be used in conjunction with Equation 2-2 to ensure regulator thermal operation is within limits. Forexample:
In this example, the LM1108 dissipates a maximum of 260mW; below the allow able limit of 508 mW . In a similar manner, Equation 2-1 and Equation 2-2 can be used to calculate maximum current and/or input voltage limits. For example, the maximum allowable VIN, is found by sustituting the maximum allowable power dissipation of 508 mW into Equation 2-1, from which VINMAX = 4.6V.
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