300mA CMOS L.D.O. Regulator
FEATURES
●
Extremely Low Supply Current(50µA,Typ.)
●
Very Low Dropout Voltage
●
300mA Output Current
●
Compatible with MLCC
●
High Output Voltage Accuracy +/- 1.4 %
●
Standardor Custom Output Voltages
●
Over Currentand Over Temperature Protection
●
Small input/output differential : 0.3V for full load
●
Moisture Sensitivity Level 3
LM1108
SOT-23
( 2.92*1.60*1.10 )
2
1
3
1. GND 2. Vin 3. Vout [A type]
1. Vin 2. Vout 3. GND [B type]
SOT-23-5L (SOT-25)
5
4
1
2
3
1. GND 2. Vin 3. Vout 4. NC 5. NC
APPLICATIONS
●
Battery Operated Systems
●
Portable Computers
●
Portable Cameras and Video Recorders
●
Medical Instruments
●
Instrumentation
●
Cellular/GSM/PHS Phones
●
Linear Post-Regulators for SMPS
●
Pagers
1
SOT-89
2
3
1. GND 2. Vin 3. Vout
ORDERING INFORMATION
Device
LM1108SF-X.X
(A type)
LM1108BSF-X.X
(B type)
LM1108GSF-X.X
(H/F)
LM1108SF5-X.X
LM1108F-X.X
Marking
HXX
BXX
HGXX
HXX
1108 X.X
Package
SOT-23 3L
SOT-23 5L
SOT-89
( "X.X" = Output Voltage
= 1.5, 1.8, 2.5, 3.0, 3.3, 3.6, 5.0 )
DESCRIPTION
The LM1108 is a fixed output,high accuracy(typically ±0.5%) CMOS low drop-out regulator.
Total supply current is typically 50µA 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 only1µF and has a maximum out put current of 300mA.
It is available in a SOT-23 & SOT-89 package
TYPICAL APPLICATION CIRCUIT
Nov. 2010 - Rev. 1.3.1
HTC
-1 -
300mA CMOS L.D.O. Regulator
ABSOLUTE MAXIMUM RATING
Characteristic
Supply Voltage
Output Current
Output Voltage
Total Power Dissipation
SOT23 PKG
SOT89 PKG
LM1108
Symbol
Vin
Iout
Vout
Pd
Topr
Tstg
Value
+6.5
300
Vss-0.3 to Vin+0.3
230
500
-40 ~ +85
260
-40 ~ +125
Unit
V
mA
V
mW
°C
°C
°C
Operating Ambient Temperature
Lead Temperature (soldering, 5 sec)
Storage Temperature
ELECTRICAL CHARACTERISTICS
%
Note.1 : Load Regulation is measured using pulse techniques with duty cycle<5%
HTC
-2-
300mA CMOS L.D.O. Regulator
Detail Description
- The LM1108 is aprecision, fixed output LDO.
LM1108
Un like bipolar regulators, the LM1108’s supply current does not increase with load current.
In addition,V
OUT
remains stable and with in regulation over theen tire 0mA to I
OUT MAX
operating load current
range, (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 V
OUT
to ground is required.
The output capacitor should have an effective series resistance greater than 0.1Ω and less than .0Ω.
1uF capacitor should be connected from V
IN
to GND if there is more than 10 inches of wire 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
-30°C, 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 exceeds150°C.
The regulator remains off until the die temperature drops to approximately 140°C.
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:
The maximum allowable power dissipation (Equation 2-2)
is a function of the maximum ambient temperature (T
AMAX
),
the maximum allowable die temperature (T
JMAX
) and the
thermal resistance from junction-to-air(θJA).
TABLE 2-1 :
-3-
HTC
300mA CMOS L.D.O. Regulator
EQUATION 2-2:
LM1108
Table 2-1 shows various values of
θJA
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.
For example:
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 V
IN
, is found by sustituting the maximum allowable power
dissipation of 508 mW into Equation 2-1, from which V
INMAX
= 4.6V.
HTC
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