LM7905C View Datasheet(PDF) - National ->Texas Instruments

Part Name

Description

Manufacturer

LM7905C

3-Terminal Negative Regulators

National ->Texas Instruments 

Design Considerations

The LM79XX fixed voltage regulator series has thermal

overload protection from excessive power dissipation inter-

nal short circuit protection which limits the circuit’s maxi-

mum current and output transistor safe-area compensation

for reducing the output current as the voltage across the

pass transistor is increased

Although the internal power dissipation is limited the junc-

tion temperature must be kept below the maximum speci-

fied temperature (125 C) in order to meet data sheet specifi-

cations To calculate the maximum junction temperature or

heat sink required the following thermal resistance values

should be used

Package

Typ

iJC

CW

Max

iJC

CW

Typ

iJA

CW

TO-220

30

50

60

PD

MAX

e

TJ Max b TA

iJC a iCA

or

TJ

Max

iJA

TA

iCA e iCS a iSA (without heat sink)

Solving for TJ

TJ e TA a PD (iJC a iCA) or

e TA a PDiJA (without heat sink)

Max

iJA

CW

40

Where

TJ e Junction Temperature

TA e Ambient Temperature

PD e Power Dissipation

iJA e Junction-to-Ambient Thermal Resistance

iJC e Junction-to-Case Thermal Resistance

iCA e Case-to-Ambient Thermal Resistance

iCS e Case-to-Heat Sink Thermal Resistance

iSA e Heat Sink-to-Ambient Thermal Resistance

Typical Applications (Continued)

Bypass capacitors are necessary for stable operation of the

LM79XX series of regulators over the input voltage and out-

put current ranges Output bypass capacitors will improve

the transient response by the regulator

The bypass capacitors (2 2 mF on the input 1 0 mF on the

output) should be ceramic or solid tantalum which have

good high frequency characteristics If aluminum electrolyt-

ics are used their values should be 10 mF or larger The

bypass capacitors should be mounted with the shortest

leads and if possible directly across the regulator termi-

nals

High Stability 1 Amp Regulator

Load and line regulation k 0 01% temperature stability s 0 2%

Determine Zener current

Solid tantalum

Select resistors to set output voltage 2 ppm C tracking suggested

4

TL H 7340 – 5

Share Link: