MCP1725 데이터 시트보기 (PDF) - Microchip Technology
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MCP1725 Datasheet PDF : 32 Pages
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MCP1725
4.0 DEVICE OVERVIEW
The MCP1725 is a high output current, Low Dropout
(LDO) voltage regulator with an adjustable delay
power-good output and shutdown control input. The
low dropout voltage of 210 mV typical at 0.5A of current
makes it ideal for battery-powered applications. Unlike
other high output current LDOs, the MCP1725 only
draws a maximum of 220 µA of quiescent current.
4.1 LDO Output Voltage
The MCP1725 LDO is available with either a fixed
output voltage or an adjustable output voltage. The
output voltage range is 0.8V to 5.0V for both versions.
4.1.1 ADJUST INPUT
The adjustable version of the MCP1725 uses the ADJ
pin (pin 7) to get the output voltage feedback for output
voltage regulation. This allows the user to set the
output voltage of the device with two external resistors.
The nominal voltage for ADJ is 0.41V.
Figure 4-1 shows the adjustable version of the
MCP1725. Resistors R1 and R2 form the resistor
divider network necessary to set the output voltage.
With this configuration, the equation for setting VOUT is:
EQUATION 4-1:
Where:
VOUT
=
VA
D
⎛
J⎝
R----1---R-+---2--R----2-⎠⎞
VOUT = LDO Output Voltage
VADJ = ADJ Pin Voltage
(typically 0.41V)
VIN
C1
4.7 µF
On
Off
MCP1725-ADJ
1 VIN
VOUT 8
2 VIN
ADJ 7
3 SHDN CDELAY 6
4 GND PWRGD 5
C3
1000 pF
VOUT
R1
C2
1 µF
R2
FIGURE 4-1:
Typical Adjustable Output
Voltage Application Circuit.
The allowable resistance value range for resistor R2 is
from 10 kΩ to 200 kΩ. Solving the equation for R1
yields the following equation:
EQUATION 4-2:
Where:
R1
=
R2
⎛
⎝
V----O----U--V--T--A--–--D--V-J---A----D---J-⎠⎞
VOUT = LDO Output Voltage
VADJ = ADJ Pin Voltage
(typically 0.41V)
4.2 Output Current and Current
Limiting
The MCP1725 LDO is tested and ensured to supply a
minimum of 0.5A of output current. The MCP1725 has
no minimum output load, so the output load current can
go to 0 mA and the LDO will continue to regulate the
output voltage to within tolerance.
The MCP1725 also incorporates an output current limit.
If the output voltage falls below 0.7V due to an overload
condition (usually represents a shorted load condition),
the output current is limited to 1.2A (typical). If the over-
load condition is a soft overload, the MCP1725 will
supply higher load currents of up to 1A. The MCP1725
should not be operated in this condition continuously as
it may result in failure of the device. However, this does
allow for device usage in applications that have higher
pulsed load currents having an average output current
value of 0.5A or less.
Output overload conditions may also result in an over-
temperature shutdown of the device. If the junction
temperature rises above 150°C, the LDO will shut
down the output voltage. See Section 4.9 “Overtem-
perature Protection” for more information on
overtemperature shutdown.
4.3 Output Capacitor
The MCP1725 requires a minimum output capacitance
of 1 µF for output voltage stability. Ceramic capacitors
are recommended because of their size, cost and
environmental robustness qualities.
Aluminum-electrolytic and tantalum capacitors can be
used on the LDO output as well. The Equivalent Series
Resistance (ESR) of the electrolytic output capacitor
must be no greater than 1 ohm. The output capacitor
should be located as close to the LDO output as is
practical. Ceramic materials X7R and X5R have low
temperature coefficients and are well within the
acceptable ESR range required. A typical 1 µF X7R
0805 capacitor has an ESR of 50 milli-ohms.
Larger LDO output capacitors can be used with the
MCP1725 to improve dynamic performance and power
supply ripple rejection performance. A maximum of
22 µF is recommended. Aluminum-electrolytic
capacitors are not recommended for low-temperature
applications of < -25°C.
DS22026B-page 16
© 2007 Microchip Technology Inc.
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