BA78 ROHM [Rohm], BA78 Datasheet - Page 10

• Manufacturer Part Number: BA78
• Description: 1A Output 78 series Regulators 500mA Output 78 series Regulators
• Manufacturer: ROHM [Rohm]

●Thermal design
●Terminal Setting and Cautions
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BA78□□Series,BA78M□□Series
www.rohm.com
Refer to the following thermal derating curves (Fig. 25, 26), when using in the status of Ta=25℃ or more.
The characteristic of IC is greatly related to the operating temperature.
When it is used in over maximum junction temperature, the elements inside IC might become weaker and be destroyed.
It is recommended to take into consideration thermal of IC.
Note that the temperatures are in the allowed temperature limits and operated within Pd.
It is necessary to operate it at junction temperature Tjmax or less to prevent IC from the thermal destruction.
Please operate IC within permissible loss Pd because the junction temperature Tj might become considerably a high
temperature even if ambient temperature Ta is normal temperature (25℃).
Power consumption Pc(W) may be expressed by the equation shown below:
Maximum Output current Io
・Calculation example
Be sure to use this IC within a power dissipation at the range of operating temperature.
・INPUT
・OUTPUT
・COMMON
Pc=(Vin-Vo)×Io+ Vin×Iｂ
permissible loss Pd≧Pc
It is recommended that a capacitor (about 0.33uF) be inserted between INPUT and COMMON.
The value of capacitor is designed suitable for the actual application.
It is recommended that a capacitor (about 0.1uF) be inserted between OUTPUT and COMMON.
A tantalum capacitor can also be used for this pin because insufficient capacitors may cause oscillation by a temperature
change.
Keep the no voltage drop between Ground level of set board and IC.
When there is the voltage difference, setting voltage becomes inaccuracy and unstable.
It is recommended to connect by wide, short pattern, and lower the inpedance.
Ex.1) Ta=85℃, Vin =7.5V, Vo=5.0V
Io≦400ｍA
Io
Io
≦
≦
1.04
Fig.25 Thermal derating curve (TO220CP-3)
Pd
Vin

25
20
15
10
7.5

5
0
Vin

7.5
0
(1) 22.0
(2) 2.0

Vo

5.0

AMBIENT TEMPERATURE : Ta[ ℃ ]
Ib
4.5m
25
(1) Mounted on infinity Alminium heat sinkθj-c=5.7(℃/W)
(2) Using an IC aloneθj-a=62.5℃/W
50
MAX
can be calculated in thermal design.
75
100
125
150
Using TO220CP-3 alone
θ ja=62.5 ℃ /W → 16mW/ ℃
Pd=1.04W at 85 ℃
10/12
Vin : Input Voltage
Vo : Output Voltage
Io
Ib
Fig.26 Thermal derating curve (TO252-3)
12.5
: Output Current
: Bias current
7.5
2.5
10
5
0
0
(1) 10.0
(2) 1.0
AMBIENT TEMPERATURE : Ta[ ℃ ]
25
(1)
(2)
Mounted on infinity Alminium heat sinkθj-c=12.5 (℃/W)
Using an IC aloneθj-a=125.0℃/W
50
75
100
125
150
Technical Note
2009.11 - Rev.B