Datasheet

MCP1702
DS22008E-page 14  2010 Microchip Technology Inc.
6.0 APPLICATION CIRCUITS AND
ISSUES
6.1 Typical Application
The MCP1702 is most commonly used as a voltage
regulator. Its low quiescent current and low dropout
voltage makes it ideal for many battery-powered
applications.
FIGURE 6-1: Typical Application Circuit.
6.1.1 APPLICATION INPUT CONDITIONS
6.2 Power Calculations
6.2.1 POWER DISSIPATION
The internal power dissipation of the MCP1702 is a
function of input voltage, output voltage and output
current. The power dissipation, as a result of the
quiescent current draw, is so low, it is insignificant
(2.0 µA x V
IN
). The following equation can be used to
calculate the internal power dissipation of the LDO.
EQUATION 6-1:
The maximum continuous operating junction
temperature specified for the MCP1702 is +125
°C. To
estimate the internal junction temperature of the
MCP1702, the total internal power dissipation is
multiplied by the thermal resistance from junction to
ambient (R
JA
). The thermal resistance from junction to
ambient for the SOT-23A pin package is estimated at
336°C/W.
EQUATION 6-2:
The maximum power dissipation capability for a
package can be calculated given the junction-to-
ambient thermal resistance and the maximum ambient
temperature for the application. The following equation
can be used to determine the package maximum
internal power dissipation.
EQUATION 6-3:
EQUATION 6-4:
EQUATION 6-5:
Package Type = SOT-23A
Input Voltage Range = 2.8V to 3.2V
V
IN
maximum = 3.2V
V
OUT
typical = 1.8V
I
OUT
= 150 mA maximum
MCP1702
GND
V
OUT
V
IN
C
IN
1 µF Ceramic
C
OUT
1µF Ceramic
V
OUT
V
IN
(2.8V to 3.2V)
1.8V
I
OUT
150 mA
P
LDO
V
IN MAX 
V
OUT MIN
–I
OUT MAX 
=
Where:
P
LDO
= LDO Pass device internal
power dissipation
V
IN(MAX)
= Maximum input voltage
V
OUT(MIN)
= LDO minimum output voltage
T
JMAX
P
TOTAL
R
JA
 T
AMAX
+=
Where:
T
J(MAX)
= Maximum continuous junction
temperature
P
TOTAL
= Total device power dissipation
R
JA
Thermal resistance from
junction to ambient
T
AMAX
= Maximum ambient temperature
P
DMAX
T
JMAX
T
AMAX
–
R
JA
---------------------------------------------------=
Where:
P
D(MAX)
= Maximum device power
dissipation
T
J(MAX)
= Maximum continuous junction
temperature
T
A(MAX)
Maximum ambient temperature
R
JA
= Thermal resistance from
junction to ambient
T
JRISE
P
DMAX
R
JA
=
Where:
T
J(RISE)
= Rise in device junction
temperature over the ambient
temperature
P
TOTAL
= Maximum device power
dissipation
R
JA
Thermal resistance from
junction to ambient
T
J
T
JRISE
T
A
+=
Where:
T
J
= Junction Temperature
T
J(RISE)
= Rise in device junction
temperature over the ambient
temperature
T
A
Ambient temperature