LM1117 查看數據表（PDF） - HTC Korea

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LM1117

1A L.D.O. VOLTAGE REGULATOR

HTC Korea 

1A L.D.O. VOLTAGE REGULATOR

LM1117S/RS/F

Maximum Output Current Capability

The LM1117 can deliver a continuous current of 1A over the full operating junction temperature range. However, the

current is limited by the restriction of power dissipation which differs from packages. A heat sink may be required

depending on the maximum power dissipation and maximum ambient temperature of application. With respect to th

applied package, the maximum output current of 1A may be still undeliverable due to the restriction of the power diss

of LM1117. Under all possible conditions, the junction temperature must be within the range specified under

operating conditions. The temperatures over the device are given by:

TC = TA + PD X θCA

TJ = TC + PD X θJC

TJ = TA + PD X θJA

TJ is the junction temperature, TC is the case temperature, TA is the ambient temperature, PD is the total power dissi

of the device, θCA is the thermal resistance of case-to-ambient, θJC is the thermal resistance of junction-to-case,

and θJA is the thermal resistance of junction to ambient. The total power dissipation of the device is given by

PD = PIN – POUT = (VIN X IIN)–(VOUT X IOUT)

= (VIN X (IOUT+IGND)) – (VOUT X IOUT) = (VIN - VOUT) X IOUT + VIN X IGND

where IGND is the operating ground current of the device which is specified at the Electrical Characteristics. The max

allowable temperature rise (TRmax) depends on the maximum ambient temperature (TAmax) of the application

and the maximum allowable junction temperature (TJmax):

TRmax = TJmax – TAmax

The maximum allowable value for junction-to-ambient thermal resistance, θ JA, can be calculated using the formula:

θJA = TRmax / PD

LM1117 is available in SOT223, TO252 packages. The thermal resistance depends on amount of copper area or he

and on air flow. If the maximum allowable value of θJA calculated above is over 130°C/W for SO-223 package, over

for TO252 package, no heat sink is needed since the package can dissipate enough heat to satisfy these

requirements. If the value for allowable θJA falls near or below these limits, a heat sink or proper area of cop

plane is required. In summary, the absolute maximum ratings of thermal resistances are as follow:

Absolute Maximum Ratings of Thermal Resistance

Characteristic

Symbol

Thermal Resistance Junction-To-Ambient / SOT223 θJA-SOT223

Thermal Resistance Junction-To-Ambient / TO252

θJA-TO252

Thermal Resistance Junction-To-Ambient / SOT89

θJA-SOT89

No heat sink / No air flow / No adjacent heat source / 0.066 inch2 copper area

Max. Rating

130

93

315

Unit

°C/W

°C/W

°C/W

Jan. 2007 - Rev 1.0

11

HTC

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