MAX8510 Maxim, MAX8510 Datasheet - Page 6

• Manufacturer Part Number: MAX8510
• Description: Ultra-Low-Noise / High PSRR / Low-Dropout /120mA Linear Regulators in SC70
• Manufacturer: Maxim

The MAX8510/MAX8511/MAX8512 are ultra-low-noise,
low-dropout, low-quiescent current linear regulators
designed for space-restricted applications. The parts
are available with preset output voltages ranging from
1.5V to 4.5V in 100mV increments. These devices can
supply loads up to 120mA. As shown in the Functional
Diagram, the MAX8510/MAX8511 consist of an innova-
tive bandgap core and noise bypass circuit, error
amplifier, P-channel pass transistor, and internal feed-
back voltage-divider. The MAX8512 allows for
adjustable output with an external feedback network.
The 1.225V bandgap reference is connected to the
error amplifier’s inverting input. The error amplifier com-
pares this reference with the feedback voltage and
amplifies the difference. If the feedback voltage is
lower than the reference voltage, the pass-transistor
gate is pulled low. This allows more current to pass to
the output and increases the output voltage. If the feed-
back voltage is too high, the pass transistor gate is
pulled high, allowing less current to pass to the output.
The output voltage is fed back through an internal resis-
tor voltage-divider connected to the OUT pin.
An external bypass capacitor connected to BP
(MAX8510) reduces noise at the output. Additional
blocks include a current limiter, thermal sensor, and
shutdown logic.
The MAX8510/MAX8511/MAX8512 feature a 1Ω (typ) P-
channel MOSFET pass transistor. This provides several
advantages over similar designs using a PNP pass
transistor, including longer battery life. The P-channel
MOSFET requires no base drive, which considerably
reduces quiescent current. PNP-based regulators
Ultra-Low-Noise, High PSRR, Low-Dropout,
120mA Linear Regulators in SC70
6
MAX8510
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—
—
1
2
3
4
5
Internal P-Channel Pass Transistor
MAX8511
PIN
—
—
1
2
3
4
5
Detailed Description
MAX8512
—
—
1
2
3
4
5
NAME
SHDN
GND
N.C.
OUT
BP
FB
IN
Unregulated Input Supply
Ground
Shutdown. Pull low to disable the regulator.
Noise Bypass for Low-Noise Operation. Connect a 10nF capacitor from
BP to OUT. It is short to OUT in shutdown mode.
Not Internally Connected
Adjustable Output Feedback Point
Regulated Output Voltage. Bypass with a capacitor to GND. See the
Capacitor Selection and Regulator Stability section for more details.
waste considerable current in dropout when the pass
transistor saturates. They also use high base-drive cur-
rent under heavy loads. The MAX8510/MAX8511/
MAX8512 do not suffer from these problems and con-
sume only 40µA of quiescent current in light load and
220µA in dropout (see the Typical Operating
Characteristics).
The MAX8510/MAX8511 are supplied with factory-set
output voltages from 1.5V to 4.5V, in 100mV increments
(see Ordering Information). The MAX8512 features a
user-adjustable output through an external feedback
network (see the Typical Operating Circuits).
To set the output of the MAX8512, use the following
equation:
where R2 is chosen to be less than 240kΩ and V
1.225V. Use 1% or better resistors.
The MAX8510/MAX8511/MAX8512 feature a low-power
shutdown mode that reduces quiescent current less
than 1µA. Driving SHDN low disables the voltage refer-
ence, error amplifier, gate-drive circuitry, and pass
transistor (see the Functional Diagram), and the device
output enters a high-impedance state. Connect SHDN
to IN for normal operation.
The MAX8510/MAX8511/MAX8512 include a current
limiter, which monitors and controls the pass transis-
tor’s gate voltage, limiting the output current to 200mA.
R
1
FUNCTION
=
R X
2
Output Voltage Selection



V
V
OUT
REF
Pin Description
-
1



Current Limit
Shutdown
REF
=