MAX8863 ON Semiconductor, MAX8863 Datasheet - Page 5

• Manufacturer Part Number: MAX8863
• Description: 120 mA Linear Regulator
• Manufacturer: ON Semiconductor

Shutdown
turning off the pass transistor, control circuit, reference, and
all biases. This reduces the supply current to 0.1 nA, typical.
For normal operation, connect SHDN to IN. When the
MAX8863 is placed in shutdown mode, the output voltage
is actively discharged to ground.
Current Limit
controls the pass transistor’s gate voltage. It estimates the
output current, limiting it to 280 mA. The current limit
should be considered 150 mA (min) to 410 mA (max) for
design purposes. The output can be shorted to ground
indefinitely without damaging the device.
Thermal Overload Protection
which limits total power dissipation. The thermal sensor
signals the shutdown logic to turn off the pass transistor
when the junction temperature exceeds T
allows the IC’s junction temperature to cool by 20 C before
the thermal sensor turns the pass transistor back on. This
results in a pulsed output during continuous thermal
overload conditions.
thermal events. High load currents and high input–output
differential voltages may cause a momentary overshoot of
2.0% to 8.0% for 200 msec when the load is removed. This
can be avoided by raising the minimum load current from
0 A (+125 C) to 100
junction temperature rating of +150 C should not be
exceeded for continuous operation.
Operating Region and Power Dissipation
the thermal resistance of the case and circuit board, the rate
of air flow, and the temperature difference between the die
junction and ambient air. The devices’ power dissipation is
P = I
dissipation is:
where (T
devices’ die junction and the surrounding air, and Q
thermal resistance of the chosen package to the surrounding
air.
to ground and channels heat away. The GND pin should be
connected to ground with a large pad or ground plane.
Low input on SHDN shuts down the MAX8863 by
The current limiter on the MAX8863 monitors and
The MAX8863 features thermal overload protection,
This feature is designed to protect the MAX8863 during
The MAX8863’s maximum power dissipation depends on
The devices’ GND pin provides an electrical connection
OUT
J
– T
(V
A
IN
) is the temperature difference between the
P MAX + (T J * T A ) Q JA
– V
OUT
); resulting maximum power
A (+150 C). The maximum
J
= +170 C. This
JA
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is the
MAX8863
5
APPLICATIONS INFORMATION
Capacitor Selection and Regulator Stability
the output should generally be used on the MAX8863. For
better supply–noise rejection and transient response, larger
input capacitor values and lower ESR should be used. If the
device is several inches from the power source or if large,
fast transients are expected, a higher–value input capacitor
(10 F) may be required.
response, stability, and power–supply rejection. A minimum
of 1.0 F is recommended for stable operation over the full
temperature range with load currents up to 120 mA.
Noise
(350 V
rejection
applications that include analog–to–digital converters of
greater than 12 bits.
Power–Supply Rejection and Operation from
Sources Other than Batteries
frequencies, rolling off above 300 Hz. Power supply noise
rejection is primarily controlled by the output capacitor at
frequencies of more than 20 KHz.
improved when operating from sources other than batteries
by increasing the values of the input and output capacitors,
and using passive filtering techniques.
Load Transient Considerations
the load current from 0 mA to 50 mA is 12 mV. To lessen
transient spikes, increase the output capacitor’s value, and
decrease its ESR.
Input–Output (Dropout) Voltage
usable supply voltage. This determines the useful
end–of–life battery voltage for battery–powered systems.
Since the MAX8863 uses a P–channel MOSFET pass
transistor, the devices’ dropout voltage is a function of
R
DS(ON)
A 1.0 F capacitor on the input, and a 1.0 F capacitor on
Using large output capacitors may improve load–transient
During normal operation, the MAX8863 have low
Power–supply rejection for the MAX8863 is 62 dB at low
Supply noise rejection and transient response can be
With the MAX8863, typical overshoot for step changes in
A regulator’s dropout voltage determines the lowest
RMS
multiplied by the load current.
specifications
) output noise. The ADC’s power–supply
should
be
considered
for