TK11250C Toko America, TK11250C Datasheet - Page 16

• Manufacturer Part Number: TK11250C
• Description: (TK112xxC) LDO Regulator
• Manufacturer: Toko America

TOKO Inc.
Layout
The package loss is limited at the temperature that the internal temperature sensor works (about 150 C).
Therefore, the package loss is assumed to be an internal limitation. There is no heat radiation
characteristic of the package unit assumed because of the small size. Heat is carried away by the device
being installed on the PCB. This value changes by the material and the copper pattern etc. of the PCB.
The losses are approximately 600mW (SOT-23L) : 900mW(SOT-89). Enduring these losses becomes
possible in a lot of applications operating at 25 C.
Determining the thermal resistance when mounted on a PCB.
The operating chip junction temperature is shown by
Tj= ja
Pd is a value when the overtemperature sensor is made to work.
Mount the IC on the print circuit board. Short between the output pin and ground. after that, raise input
voltage from 0V to evaluated voltage (see*1) gradually.
At shorted the output pin, the power dissipation P
The input current decreases gradually as the temperature of the chip becomes high. After a while, it
reaches the thermal equilibrium. Use this currrent value at the thermal equilibrium. In almost all the
cases, it shows 600mW(SOT23L-6)：900mW(SOT89-5) or more.
Pd is easily obtained.
*1 In the case that the power, Vin
Pd is obtained by the normal temperature in degrees. The current that can be used at the highest
operating temperature is obtained from the graph of the figure below.
DPd
Please do derating with 4mW/ C at
Pd=600mW and 25 C or more. Thermal
resistance is ( ja=250 C / W).
Pd(mW)
Pd
dissipation in a moment, there is a possibility that the IC is destroyed before internal thermal protection works.
The maximum current that can be used at the highest operating temperature is:
Iout
Vin
on/off
0
SOT23L-6
Pd + Ta.
PCB Material : Glass epoxy t=0.8mm
25
2
5
DPd
50
(75)
4
Tj of the IC is set to about 150 C.
(Vinmax
Vout
100
3
Ishort(Short Circuit Current), becomes more than twice of the maximum rating of its power
150 C
Vout).
Please do derating with 7.2mW/ C at
Pd=900mW
Thermal resistance is ( ja=138 C / W)
Vout
IC Data Sheet
GC3-H026 A
SOT89-5
1. Pd is obtained (Vin
2. Pd is plotted on the horizontal line to 25 C.
3. Pd is connected with the point of 150 C by the straight line
(bold face line).
4. A line is extended vertically above the point of use temperature in the
5. Extend the intersection of the derating curve (fat solid line) and (broken
6. DPd
design. For instance, 75 C is assumed (broken line).
line) to the left and read the Pd value.
and
D
can be expressed as Pd=Vin
(Vinmax
25 C
On/off
or
Procedure (Do when PCB mounted).
Vout)=Iout (at 75 C)
more.
Iin when the output side is short-circuited).
Vin
Ta (Ta=25 C)
150 = ja
900
600
ja
ja = (125/ pd) ( C / mW)
Pd(mW)
0
0
Pd = 125
25
Derating Curve
Iin.
pd + 25
SOT-89
-7.2mW/ C
TK112xxC
50 C
Page 16
(85) C
SOT-23- L
-4.8mW/ C
100
150