MAX15104EWL データシートの表示（PDF） - Maxim Integrated
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MAX15104EWL Datasheet PDF : 10 Pages
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MAX15104
Small 2A, Low-Dropout Linear Regulator
in a 2.7mm x 1.6mm Package
Enable
A logic-low on EN disables the MAX15104. In shutdown,
the pass transistor, control circuitry, reference, and all
biases are turned off, reducing supply current to typically
1µA. Connect EN to IN for normal operation. In shutdown,
the soft-start capacitor is discharged using an internal
pulldown resistance.
Soft-Start
As shown in the Typical Operating Circuit, the MAX15104
uses a gM stage and integrating capacitor CSS to control
the regulator’s feedback set point. When EN is driven low,
the soft-start capacitor is discharged. When EN is driven
high or power is applied to the device, a constant 9.2µA
current charges the soft-start capacitor. At startup, the
feedback set point increases linearly, which reduces the
inrush supply current.
tSS = 6.315 x 10-5 x CSS
where CSS is in nF. Use capacitor values between 30nF
to 100nF with voltage ratings greater than 5V.
Because this ramp is applied to the current-limit com-
parator, the actual time for the output voltage to ramp up
depends on the load current and output capacitor. Leave
SS_BYP unconnected to disable soft-start.
Foldback Current Limiting
The MAX15104 features a 2.5A current limit when the
output voltage is in regulation. When the voltage at the
output drops to 17% of its nominal value, the current
limit exponentially folds back to 1.4A. The output can be
shorted to ground for an indefinite period of time without
damaging the device. Avoid continuous output current of
greater than 2A to prevent damage to the regulator.
Thermal-Overload Protection
A thermal-overload circuit limits total power dissipation in
the MAX15104. When the junction temperature exceeds
TJ = +160°C, the thermal sensor turns off the pass tran-
sistor, allowing the IC to cool. The thermal sensor turns
the pass transistor on once the IC’s junction temperature
drops approximately 15°C. Continuous short-circuit condi-
tions will consequently result in a foldback limited output.
Thermal-overload protection is designed to safeguard the
MAX15104 in the event of fault conditions. For continuous
operation, do not exceed the junction temperature rating
of TJ = +125°C.
Operating Region and Power Dissipation
The power dissipation across the device is P = IOUT
(VIN - VOUT). The resulting maximum power dissipation is:
PMAX = [(TJ(MAX) - TA)/(θJA)]
where (TJ(MAX) - TA) is the temperature difference
between the maximum allowed die junction (+150°C) and
the surrounding air. Figure 1 shows the allowable power
dissipation for typical PCBs at +25°C, +50°C, and +70°C
ambient temperatures (refer to the MAX15104 EV kit).
Applications Information
Capacitor Selection and Regulator Stability
Capacitors are required at the MAX15104’s input and out-
put. Connect at least a 2.2µF capacitor between IN and
GND (CIN) and a 22µF capacitor between OUT and GND
(COUT). 10μF can be used for lower current operation (1A
for example). Use only surface-mount ceramic capacitors
that have low equivalent series resistance (ESR). Make
the input and output traces at least 2.5mm wide, and con-
nect CIN and COUT within 6mm of the IC to minimize the
impact of PCB trace inductance.
The output capacitor’s ESR can affect stability and output
noise. Use capacitors with 50mΩ or less ESR to ensure
stability and optimum transient response. This is par-
ticularly true in applications with very low output voltage
(< 2V) and high output current (> 0.5A).
Since some capacitor dielectrics can vary over bias volt-
age and temperature, consult the capacitor manufacturer
specifications to ensure that the capacitors meet these
requirements over all combinations of operating voltage
and temperature.
2.5
2.0
TA = +25°C
1.5
1.0
TA = +50°C
0.5
TA = +70°C
TJ = +125°C (BASED ON MAX15102 EV KIT)
0
0
1
2
3
4
5
INPUT-OUTPUT DIFFERENTIAL VOLTAGE (V)
Figure 1. Maximum Output Current Curves
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