MAX15104 Datasheet, PDF (8/10 Pages) Maxim Integrated Products – Small 2A, Low-Dropout Linear Regulator in a 2.7mm x 1.6mm Package

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
1FA. 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 g_M stage and integrating capacitor C_SS 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
9.2FA current charges the soft-start capacitor. At startup,
the feedback set point increases linearly, which reduces
the inrush supply current.
t_SS = 6.315 x 10^-5 x C_SS
where C_SS 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
T_J = +160NC, 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 15NC. 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 contin-
uous operation, do not exceed the junction temperature
rating of T_J = +125NC.
Operating Region and Power Dissipation
The power dissipation across the device is P = I_OUT
(V_IN - V_OUT). The resulting maximum power dissipation is:
P_MAX = [(T_J(MAX) - T_A)/(B_JA)]
where (T_J(MAX) - T_A) is the temperature difference
between the maximum allowed die junction (+150NC) and
the surrounding air. Figure 1 shows the allowable power
dissipation for typical PCBs at +25NC, +50NC, and +70NC
ambient temperatures (refer to the MAX15104 EV kit).
Applications Information
Capacitor Selection and Regulator Stability
Capacitors are required at the MAX15104’s input and
output. Connect at least a 2.2FF capacitor between IN
and GND (C_IN) and a 22FF capacitor between OUT and
GND (C_OUT). 10µF can be used for lower current opera-
tion (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 connect C_IN and C_OUT 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 50mI 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 = +25NC
1.5
1.0
T_A = +50NC
0.5
TA = +70NC
TJ = +125NC (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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