MAX1818 Maxim, MAX1818 Datasheet - Page 5

• Manufacturer Part Number: MAX1818
• Description: 500mA Low-Dropout Linear Regulator in SOT23
• Manufacturer: Maxim

The MAX1818 is a low-dropout, low-quiescent-current
linear regulator designed primarily for battery-powered
applications. The device supplies loads up to 500mA
and is available with preset output voltages. As illustrat-
ed in Figure 1, the MAX1818 consists of a 1.25V refer-
ence, error amplifier, P-channel pass transistor, and
internal feedback voltage-divider.
The 1.25V reference is connected to the error amplifier,
which compares this reference with the feedback volt-
age and amplifies the difference. If the feedback volt-
age is lower than the reference voltage, the
(V
IN
PIN
1
2
3
4
5
6
= (V
OUT
SHUTDOWN
NAME
SHDN
+ 500mV) or +2.5V, whichever is greater; SHDN = IN, C
VOLTAGE
POK
GND
OUT
SET
IN
V
POK
OUT
_______________________________________________________________________________________
Regulator Input. Supply voltage can range from 2.5V to 5.5V. Bypass with a 1µF capacitor to GND (see
Capacitor Selection and Regulator Stability).
Open-Drain POK Output. POK remains low while the output voltage (V
Connect a 100kΩ pull-up resistor from POK to OUT to obtain an output voltage.
Active-Low Shutdown Input. A logic low reduces supply current below 15µA. In shutdown, the POK output is
low, and OUT is high impedance. Connect to IN for normal operation.
Ground
Voltage-Setting Input. Connect to GND for preset output. Connect to a resistive voltage-divider between
OUT and GND to set the output voltage between 1.25V and 5.0V.
Regulator Output. Sources up to 500mA. Bypass with a 3.3µF low-ESR capacitor to GND. Use a 4.7µF
capacitor for output voltages below 2V.
Detailed Description
SHUTDOWN WAVEFORM
200µs/div
MAX1818 toc12
Typical Operating Characteristics (continued)
0
0
2V/div
0
Linear Regulator in SOT23
IN
pass-transistor gate is pulled lower, which allows more
current to pass to the output and increases the output
voltage. If the feedback voltage is too high, the pass-
transistor gate is pulled up, allowing less current to
pass to the output.
The output voltage is fed back through either an inter-
nal resistive divider connected to OUT or an external
resistor network connected to SET. The Dual Mode
comparator examines V
path. If V
is used and the output is regulated to the factory-preset
voltage.
= 1µF, C
FUNCTION
500mA Low-Dropout
1.11
1.10
1.09
1.08
1.07
1.06
1.05
1.04
1.03
1.02
1.01
1.00
SET
OUT
2.5
V
is below 50mV, the internal feedback path
= 3.3µF, T
OUT(NOM)
SHORT-CIRCUIT CURRENT LIMIT
3.0
vs. SUPPLY VOLTAGE
= +2V
SUPPLY VOLTAGE (V)
OUT
3.5
A
) is below the POK threshold.
= +25°C, unless otherwise noted.)
SET
4.0
and selects the feedback
4.5
Pin Description
5.0
5.5
5