MCP1726 View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'MCP1726' PDF : 30 Pages View PDF
MCP1726
5.0 APPLICATION CIRCUITS/
ISSUES
5.1 Typical Application
The MCP1726 is used for applications that require high
LDO output current and a power good output.
VIN = 3.3V
C1
10 µF
On
Off
MCP1726-2.5
1 VIN
VOUT 8
2 VIN
VOUT 7
3 SHDN CDELAY 6
4 GND PWRGD 5
VOUT = 2.5V @ 1A
R1
10kΩ
C2
10 µF
C3
1000 pF
PWRGD
FIGURE 5-1:
Typical Application Circuit.
5.1.1 APPLICATION CONDITIONS
Package Type = 3x3DFN8
Input Voltage Range = 3.3V ± 10%
VIN maximum = 3.63V
VIN minimum = 2.97V
VOUT typical = 2.5V
IOUT = 1.0A maximum
5.2 Power Calculations
5.2.1 POWER DISSIPATION
The internal power dissipation within the MCP1726 is a
function of input voltage, output voltage, output current
and quiescent current. The following equation can be
used to calculate the internal power dissipation for the
LDO.
EQUATION 5-1:
PLDO = (VIN(MAX )) – VOUT(MIN)) × IOUT(MAX))
PLDO = LDO Pass device internal power
dissipation
VIN(MAX) = Maximum input voltage
VOUT(MIN) = LDO minimum output voltage
In addition to the LDO pass element power dissipation,
there is power dissipation within the MCP1726 as a
result of quiescent or ground current. The power dissi-
pation as a result of the ground current can be
calculated using the following equation:
EQUATION 5-2:
PI(GND) = VIN(MAX) × IVIN
PI(GND) = Power dissipation due to the
quiescent current of the LDO
VIN(MAX) = Maximum input voltage
IVIN = Current flowing in the VIN pin with no
LDO output current (LDO quiescent
current)
The total power dissipated within the MCP1726 is the
sum of the power dissipated in the LDO pass device
and the P(IGND) term. Because of the CMOS construc-
tion, the typical IGND for the MCP1726 is 140 µA.
Operating at a maximum of 3.63V results in a power
dissipation of 0.51 milli-Watts. For most applications,
this is small compared to the LDO pass device power
dissipation and can be neglected.
The maximum continuous operating junction tempera-
ture specified for the MCP1726 is +125°C. To estimate
the internal junction temperature of the MCP1726, the
total internal power dissipation is multiplied by the ther-
mal resistance from junction to ambient (RθJA) of the
device. The thermal resistance from junction to ambi-
ent for the 3x3DFN package is estimated at 41° C/W.
EQUATION 5-3:
TJ(MAX) = PTOTAL × RθJA + TAMAX
TJ(MAX) = Maximum continuous junction
temperature
PTOTAL = Total device power dissipation
RθJA = Thermal resistance from junction-to-
ambient
TAMAX = Maximum ambient temperature
DS21936C-page 18
© 2007 Microchip Technology Inc.
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