2010 Microchip Technology Inc. DS22051D-page 11
MCP1801
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: MCP1801 PIN FUNCTION TABLE
3.1 Unregulated Input Voltage (V
IN
)
Connect V
IN
to the input unregulated source voltage.
Like all low dropout linear regulators, low source
impedance is necessary for the stable operation of the
LDO. The amount of capacitance required to ensure
low source impedance will depend on the proximity of
the input source capacitors or battery type. For most
applications, 0.1 µF of capacitance will ensure stable
operation of the LDO circuit. The type of capacitor used
can be ceramic, tantalum, or aluminum electrolytic. The
low ESR characteristics of the ceramic will yield better
noise and PSRR performance at high frequency.
3.2 Ground Terminal (GND)
Regulator ground. Tie GND to the negative side of the
output and the negative side of the input capacitor.
Only the LDO bias current (25 µA typical) flows out of
this pin; there is no high current. The LDO output
regulation is referenced to this pin. Minimize voltage
drops between this pin and the negative side of the
load.
3.3 Shutdown Input (SHDN)
The SHDN input is used to turn the LDO output voltage
on and off. When the SHDN
input is at a logic-high
level, the LDO output voltage is enabled. When the
SHDN input is pulled to a logic-low level, the LDO
output voltage is disabled and the LDO enters a low
quiescent current shutdown state where the typical
quiescent current is 0.01 µA. The SHDN
pin does not
have an internal pull-up or pull-down resistor. The
SHDN pin must be connected to either V
IN
or GND to
prevent the device from becoming unstable.
3.4 Regulated Output Voltage (V
OUT
)
Connect V
OUT
to the positive side of the load and the
positive terminal of the output capacitor. The positive
side of the output capacitor should be physically
located as close to the LDO V
OUT
pin as is practical.
The current flowing out of this pin is equal to the DC
load current.
Pin No.
SOT-23-5
Name Function
1V
IN
Unregulated Supply Voltage
2 GND Ground Terminal
3 SHDN
Shutdown Input
4 NC No Connection
5V
OUT
Regulated Voltage Output
