TC1017 Microchip Technology, TC1017 Datasheet - Page 13

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

FIGURE 5-2:
Ambient Temperature (SC-70 package).
5.3
The TC1017 is also available in a SOT-23 package for
improved thermal performance. The thermal resistance
for the SOT-23 package is approximately 255°C/W
when the copper area used in the printed circuit board
layout is similar to the JEDEC J51-7 low 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
power dissipation within the LDO to be:
EQUATION:
To
capability, the following equation is used:
P
2003 Microchip Technology Inc.
D
determine
=
160
140
120
100
IN
80
60
40
20
0
Power Dissipation: SOT-23
V
-40
x I
IN
P
–
GND
D
V
-15
=
O UT
the
term is typically very small when
Ambient Temperature (°C)
IN
V
-V
IN
10
Maximum Current vs.
OUT
maximum
–
I
LOAD
V
) x I
OU T
35
+
LOAD
V
IN
60
I
LO AD
term, simplifying the
power
V
I
IN
GND
85
- V
OUT
dissipation
110
= 1V
EQUATION:
Given the following example:
Find:
1.
2.
3.
In this example, the TC1017 dissipates approximately
158.5 mWatts and the junction temperature is raised
40.5°C over the ambient. The absolute maximum
power dissipation is 157 mW when given a maximum
ambient temperature of +85°C.
Input voltage, output voltage or load current limits can
also be determined by substituting known values in the
power dissipation equations.
Figure 5-3 and Figure 5-4 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.
Where:
Internal power dissipation:
Maximum allowable ambient temperature:
Maximum
desired ambient:
T
P
T
T
R
A_MAX
DMA X
A_MAX
J_MAX
I
V
JA
LOAD
P
OUT
V
D MAX
T
IN
=
=
=
=
=
=
A
=
P
= the thermal resistance from
= the maximum junction
= the maximum ambient
D
T
158.5mW
84.5 C
=
=
=
=
allowable
125 C 40.5 C
V
4.1V 2.85
125 C 158.5mW
J_MAX
=
=
junction to air
=
temperature allowed
temperature
IN_MAX
=
T
----------------------------- -
125 C 85 C
---------------------------------- -
157mW
3.0V to 4.1V
2.85V ±2.5%
120 mA (output current)
+85°C (max. desired ambient)
------------------------------------------------ -
–
J_MAX
T
255 C/W
–
J_MAX
–
–
R
P
–
DMAX
JA
V
–
–
R
OUT_MIN
power
T
–
A
J A
0.975
T
A_MAX
R
TC1017
DS21813B-page 13
255 C/W
JA
dissipation
I
LOAD
120mA
at