MCP1703T-1502E/MC MICROCHIP [Microchip Technology], MCP1703T-1502E/MC Datasheet - Page 18

• Manufacturer Part Number: MCP1703T-1502E/MC
• Description: 250 mA, 16V, Low Quiescent Current LDO Regulator
• Manufacturer: MICROCHIP [Microchip Technology]

MCP1703
6.3
Internal power dissipation, junction temperature rise,
junction temperature and maximum power dissipation
are calculated in the following example. The power
dissipation, as a result of ground current, is small
enough to be neglected.
6.3.1
Device Junction Temperature Rise
The internal junction temperature rise is a function of
internal power dissipation and the thermal resistance
from junction to ambient for the application. The
thermal resistance from junction to ambient (Rθ
derived from an EIA/JEDEC standard for measuring
thermal resistance for small surface mount packages.
The EIA/JEDEC specification is JESD51-7, “High
Effective Thermal Conductivity Test Board for Leaded
Surface Mount Packages”. The standard describes the
test method and board specifications for measuring the
thermal resistance from junction to ambient. The actual
thermal resistance for a particular application can vary
depending on many factors, such as copper area and
thickness. Refer to AN792, “A Method to Determine
How Much Power a SOT23 Can Dissipate in an
Application”,
regarding this subject.
Junction Temperature Estimate
To estimate the internal junction temperature, the
calculated temperature rise is added to the ambient or
offset temperature. For this example, the worst-case
junction temperature is estimated below.
DS22049D-page 18
Package
Input Voltage:
LDO Output Voltages and Currents
Maximum Ambient Temperature
Internal Power Dissipation
Internal Power dissipation is the product of the LDO
output current times the voltage across the LDO
(V
Package Type: SOT-23A
IN
P
to V
T
LDO(MAX)
T
T
J(RISE)
T
JRISE
JRISE
A(MAX)
Voltage Regulator
OUT
V
P
P
I
OUT
OUT
LDO
LDO
POWER DISSIPATION EXAMPLE
V
IN
).
= P
= 152.7 milli-Watts x 336.0
= 51.3
(DS00792),
= 2.7V to 4.8V
= 1.8V
= 50 mA
= +40°C
= (V
= (4.8V - (0.97 x 1.8V)) x 50 mA
= 152.7 milli-Watts
TOTAL
IN(MAX)
°
C
x Rq
- V
JA
for
OUT(MIN)
more
) x I
°
C/Watt
OUT(MAX)
information
JA
) is
Maximum Package Power Dissipation at +40°C
Ambient Temperature
6.4
The MCP1703 can be used not only as a regulator, but
also as a low quiescent current voltage reference. In
many microcontroller applications, the initial accuracy
of the reference can be calibrated using production test
equipment or by using a ratio measurement. When the
initial accuracy is calibrated, the thermal stability and
line regulation tolerance are the only errors introduced
by the MCP1703 LDO. The low-cost, low quiescent
current and small ceramic output capacitor are all
advantages when using the MCP1703 as a voltage
reference.
FIGURE 6-2:
Voltage Reference.
6.5
For some applications, there are pulsed load current
events that may exceed the specified 250 mA
maximum specification of the MCP1703. The internal
current limit of the MCP1703 will prevent high peak
load demands from causing non-recoverable damage.
The 250 mA rating is a maximum average continuous
rating. As long as the average current does not exceed
250 mA, pulsed higher load currents can be applied to
the MCP1703
MCP1703 is 500 mA (T
SOT-23A (336.0°C/Watt = Rθ
SOT-89 (75°C/Watt = Rθ
SOT-223 (62.9°C/Watt = Rθ
2 µA Bias
C
1 µF
IN
P
P
P
P
P
P
D(MAX)
D(MAX)
D(MAX)
D(MAX)
D(MAX)
D(MAX)
Bridge Sensor
Voltage Reference
Pulsed Load Applications
T
T
MCP1703
V
GND
J
J
IN
= T
= 91.3°C
= (+125°C - 40°C) / 336°C/W
= 253 milli-Watts
= (+125°C - 40°C) / 75°C/W
= 1.133 Watts
= (+125°C - 40°C) / 62.9°C/W
= 1.35 Watts
V
.
OUT
Ratio Metric Reference
The typical current limit for the
JRISE
C
1 µF
Using the MCP1703 as a
A
OUT
+ T
© 2009 Microchip Technology Inc.
+25°C).
JA
A(MAX)
)
JA
JA
)
)
V
ADO
AD1
Microcontroller
REF
PIC
®