MCP1726 Microchip Technology, MCP1726 Datasheet - Page 14

• Manufacturer Part Number: MCP1726
• Description: 1A Low Voltage / Low Quiescent Current LDO Regulator
• Manufacturer: Microchip Technology

MCP1726
4.0
The MCP1726 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 220 mV at 1A of current makes
it ideal for battery-powered applications. Unlike other
high output current LDOs, the MCP1726 only draws
220 µA of quiescent current at full load.
4.1
The MCP1726 LDO is available with either a fixed
output voltage or an adjustable output voltage. The
output voltage range is 0.8V to 5.5V for both versions.
4.1.1
The adjustable version of the MCP1726 uses the ADJ
pin (pin 7) to get the output voltage feedback for output
voltage regulation. This allows the user to set the out-
put 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
MCP1726. Resistors R
divider network necessary to set the output voltage.
With this configuration, the equation for setting V
EQUATION 4-1:
FIGURE 4-1:
voltage application circuit.
The allowable resistance value range for resistor R
from 10 k
yields the following equation:
EQUATION 4-2:
DS21936B-page 14
Off
V
V
V
V
V
ADJ
ADJ
OUT
OUT
IN
On
4.7 µF
= LDO Output Voltage
= ADJ Pin Voltage (typically 0.41V)
C
DEVICE OVERVIEW
LDO Output Voltage
= LDO Output Voltage
= ADJ Pin Voltage (typically 0.41V)
1
ADJUST INPUT
to 200 k . Solving the equation for R
V
1
2
3
4
R
MCP1726-ADJ
OUT
1
V
V
SHDN
GND
=
IN
IN
R
=
Typical adjustable output
2
PWRGD
C
⎛
⎝
V
1
DELAY
V
--------------------------------
V
ADJ
1000 pF
ADJ
OUT
OUT
and R
V
⎛
⎝
8
7
6
5
C
R
------------------
ADJ
–
3
1
V
R
+
2
ADJ
2
R
form the resistor
2
⎞
⎠
⎞
⎠
R
R
V
1
2
OUT
OUT
1 µF
C2
2
is:
is
1
4.2
The MCP1726 LDO is tested and ensured to supply a
minimum of 1A of output current. The MCP1726 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 MCP1726 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 1.7A (typical). If the over-
load condition is a soft overload, the MCP1726 will sup-
ply higher load currents of up to 3A. The MCP1726
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 1A 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
The MCP1726 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 2 ohms. 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 accept-
able 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
MCP1726 to improve dynamic performance and power
supply ripple rejection performance. A maximum of
22 µF
capacitors are not recommended for low-temperature
applications of < -25°C.
Output Current and Current
Limiting
Output Capacitor
is
recommended.
© 2005 Microchip Technology Inc.
Aluminum-electrolytic