MCP1701 Microchip Technology, MCP1701 Datasheet - Page 11

• Manufacturer Part Number: MCP1701
• Description: 2 uA Low Dropout Positive Voltage Regulator
• Manufacturer: Microchip Technology

5.0
5.1
The amount of power dissipated internal to the LDO
linear regulator is the sum of the power dissipation
within the linear pass device (P-channel MOSFET) and
the quiescent current required to bias the internal refer-
ence and error amplifier. The internal linear pass
device power dissipation is calculated as shown in
Equation 5-1.
EQUATION 5-1:
The internal power dissipation, which is due to the bias
current for the LDO internal reference and error ampli-
fier, is calculated as shown in Equation 5-2.
EQUATION 5-2:
The total internal power dissipation is the sum of P
(Pass Device) and P
EQUATION 5-3:
For the MCP1701, the internal quiescent bias current is
so low (2 µA, typical) that the P
power dissipation equation can be ignored. The
maximum power dissipation can be estimated by using
the maximum input voltage and the minimum output
voltage to obtain a maximum voltage differential
between input and output. The next step would be to
multiply the maximum voltage differential by the
maximum output current.
EQUATION 5-4:
Given:
2004 Microchip Technology Inc.
T
P
P
V
AMAX
I
OUT
OUT
MAX
MAX
V
P
IN
TOTAL
THERMAL CONSIDERATIONS
Power Dissipation
P
P
D
= 3.3V to 4.1V
= 3.0V ± 2%
= 1 mA to 100 mA
= 55°C
= (4.1V – (3.0V x 0.98)) x 100 mA
= 116.0 milliwatts
D
(Pass Device) = (V
= (V
= P
P
INMAX
D
D
(Pass Device) + P
(Bias) = V
D
(Bias).
– V
OUTMIN
IN
IN
x I
– V
D
) x I
GND
OUT
(Bias) term of the
D
OUTMAX
(Bias)
) x I
OUT
D
To determine the junction temperature of the device, the
thermal resistance from junction-to-ambient must be
known. The 3-pin SOT-23 thermal resistance from
junction-to-air (R
335°C/W. The SOT-89 R
approximately 52°C/W when mounted on 1 square inch
of copper. For the TO-92, R
131.9°C/W. The R
airflow and other application-specific conditions.
The device junction temperature is determined by
calculating the junction temperature rise above
ambient, then adding the rise to the ambient
temperature.
EQUATION 5-5:
EQUATION 5-6:
EQUATION 5-7:
T
T
T
T
T
J
J
T
T
J
J
J
J
J
=
=
=
=
=
=
=
116.0 milliwatts
61°C
P
116.0 milliwatts
93.9°C
116.0 milliwatts
70.3°C
D MAX
JA
) is estimated to be approximately
JA
JUNCTION
TEMPERATURE - SOT-23
EXAMPLE:
JUNCTION
TEMPERATURE - SOT-89
EXAMPLE:
JUNCTION
TEMPERATURE - TO-92
EXAMPLE:
R
will vary with physical layout,
JA
+
52°C/W
MCP1701
JA
T
335°C/W
A
JA
131.9°C/W
is estimated to be
is estimated to be
DS21874A-page 11
+
55°C
+
55°C
+
55°C