ts2940cm33 Taiwan Semiconductor Company, Ltd. (TSC), ts2940cm33 Datasheet - Page 4

• Manufacturer Part Number: ts2940cm33
• Description: 1a Ultra Low Dropout Fixed Positive Voltage Regulator
• Manufacturer: Taiwan Semiconductor Company, Ltd. (TSC)

Application Information (Continue)
Thermal Characteristics
A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the
application. Under all possible operating conditions, the junction temperature must be within the range specified under
absolute maximum ratings. To determine if the heatsink is required, the power dissipated by the regulator, P
calculated.
The below formula shows the voltages and currents for calculating the P
IIN = IL / IG
P
Ex. P
Remark: I
The next parameter which must be calculated is the maximum allowable temperature rise.
TR(max) is calculated by the using to formula:
TR(max) = TJ(max) – TA(max)
Where: TJ(max) is the maximum allowable junction temperature, which is 125
is the maximum ambient temperature which will be encountered in the application.
Using the calculated values for TR(max) and PD, the maximum allowable value for the junction to ambient thermal
resistance, θja, can now be found:
IMPORTANT: if the maximum allowable value for is found to be ≥60
TO-263 package, ≥150
since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for θja falls
below these limits, a heatsink is required.
θja = TR(max) / PD
D
= (V
D
= 800mW + 36mW
= 836mW
= (3.3V-2.5V) * 1A + 3.3V * 11mA
IN
-V
V
I
V
G
L
OUT
IN
OUT
is output load current,
is ground current.
is input voltage
) * I
is output voltage
L
+ (V
IN
o
C/W for the TO-252 package, or ≥170
) * I
G
1A Ultra Low Dropout Voltage Regulator
4/10
o
C /W for the SOT-223 package, no heatsink is needed
o
C /W for the TO-220 package, ≥80
D
in the regulator:
o
C for commercial grade parts. T
TS2940
Version: A07
o
C/W for the
D
must be
A
(max)