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
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
