Datasheet

© 2007 Microchip Technology Inc. DS21826B-page 13
MCP1700
6.0 APPLICATION CIRCUITS &
ISSUES
6.1 Typical Application
The MCP1700 is most commonly used as a voltage
regulator. It’s low quiescent current and low dropout
voltage make 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 MCP1700 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
(1.6 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 MCP1700 is +125
°C. To
estimate the internal junction temperature of the
MCP1700, the total internal power dissipation is
multiplied by the thermal resistance from junction to
ambient (Rθ
JA
). The thermal resistance from junction to
ambient for the SOT-23 pin package is estimated at
230
°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-23
Input Voltage Range = 2.3V to 3.2V
V
IN
maximum = 3.2V
V
OUT
typical = 1.8V
I
OUT
= 150 mA maximum
MCP1700
GND
V
OUT
V
IN
C
IN
1µF Ceramic
C
OUT
1 µF Ceramic
V
OUT
V
IN
(2.3V to 3.2V)
1.8V
I
OUT
150 mA
P
LDO
V
IN MAX)()
V
OUT MIN()
–()I
OUT MAX)()
×=
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
Rθ
JA
× T
AMAX
+=
T
J(MAX)
= Maximum continuous junction
temperature.
P
TOTAL
= Total device power dissipation.
Rθ
JA
= Thermal resistance from junction to ambient.
T
AMAX
= Maximum ambient temperature.
P
DMAX()
T
JMAX()
T
AMAX()
–()
Rθ
JA
---------------------------------------------------=
P
D(MAX)
= Maximum device power dissipation.
T
J(MAX)
= Maximum continuous junction
temperature.
T
A(MAX)
= Maximum ambient temperature.
Rθ
JA
= Thermal resistance from junction to ambient.
T
JRISE()
P
DMAX()
Rθ
JA
×=
T
J(RISE)
= Rise in device junction temperature over
the ambient temperature.
P
TOTAL
= Maximum device power dissipation.
Rθ
JA
= Thermal resistance from junction to ambient.
T
J
T
JRISE()
T
A
+=
T
J
= Junction Temperature.
T
J(RISE)
= Rise in device junction temperature over
the ambient temperature.
T
A
= Ambient temperature.