TC1017 Microchip Technology, TC1017 Datasheet - Page 12

• Manufacturer Part Number: TC1017
• Description: Tiny CMOS LDO
• Manufacturer: Microchip Technology

TC1017
5.0
5.1
Integrated thermal protection circuitry shuts the
regulator
approximately 160°C. The regulator remains off until
the die temperature drops to approximately 150°C.
5.2
The TC1017 is available in the SC-70 package. The
thermal resistance
approximately 450°C/W when the copper area used in
the printed circuit board layout is similar to the
JEDEC J51-7 high thermal conductivity standard or
semi-G42-88 standard. For applications with larger or
thicker copper area, the thermal resistance can be
lowered. See AN792, “A Method to Determine How
Much Power a SOT-23 Can Dissipate in an
Application”, DS00792, for a method to determine the
thermal resistance for a particular application.
The TC1017 power dissipation capability is dependant
upon several variables: input voltage, output voltage,
load current, ambient temperature and maximum
junction temperature. The absolute maximum steady-
state junction temperature is rated at +125°C. The
power dissipation within the device is equal to:
EQUATION:
The V
compared to the (V
the power dissipation within the LDO to be:
EQUATION:
To
capability, the following equation is used:
EQUATION:
DS21813B-page 12
Where:
determine
P
IN
T
T
R
A_MAX
D
J_MAX
THERMAL CONSIDERATIONS
Thermal Shutdown
Power Dissipation: SC-70
JA
x I
=
off
P
GND
P
V
DMAX
D
IN
= the maximum junction
= the maximum ambient
= the thermal resistance from
when
=
the
–
term is typically very small when
junction to air
temperature allowed
temperature
V
IN
V
=
OUT
-V
IN
for the
maximum
----------------------------------------------
OUT
T
–
die
J_MAX
V
) x I
OU T
I
LOAD
R
temperature
–
LOAD
JA
SC-70
T
A_MAX
+
I
power
LO AD
V
term, simplifying
IN
package
I
G ND
dissipation
exceeds
is
Given the following example:
Find:
1.
2.
3.
In this example, the TC1017 dissipates approximately
158.5 mW and the junction temperature is raised 71°C
over the ambient. The absolute maximum power
dissipation is 155 mW when given a maximum ambient
temperature of 55°C.
Input voltage, output voltage or load current limits can
also be determined by substituting known values in the
power dissipation equations.
Figure 5-1 and Figure 5-2 depict typical maximum
power dissipation versus ambient temperature and
typical maximum current versus ambient temperature,
with a one volt input voltage to output voltage
differential, respectively.
FIGURE 5-1:
Ambient Temperature (SC-70 package).
Internal power dissipation:
Maximum allowable ambient temperature:
Maximum
desired ambient:
P
T
400
350
300
250
200
150
100
DMAX
50
A_MAX
0
I
-40
V
LOAD
OUT
V
T
IN
A
=
=
=
=
=
=
=
-15
allowable power
158.5mW
P
=
=
=
=
T
54 C
V
4.1V 2.85
125 C 158.5mW
125 C 71 C
D
J_MAX
IN_MAX
Ambient Temperature (°C)
3.0V to 4.1V
2.85V ±2.5%
120 mA (output current)
55°C (max. desired ambient)
=
=
=
10
–
Power Dissipation vs.
T
----------------------------- -
125 C 55 C
---------------------------------- -
155mW
J_MAX
–
–
–
450 C/W
2003 Microchip Technology Inc.
R
–
P
35
V
DM AX
JA
OUT_MIN
–
–
0.975
T
60
A
dissipation
R
450 C/W
85
J A
120mA
I
LOAD
110
at