MAX15009 Datasheet, PDF (19/23 Pages) Maxim Integrated Products – Automotive 300mA LDO Regulators with Switched Output and Overvoltage Protector

Automotive 300mA LDO Regulators with
Switched Output and Overvoltage Protector
where V_SOURCE = (V_OV x 0.04) + V₂ in volts, and C_rss
is the MOSFET’s reverse transfer capacitance in pF.
Any external capacitance between GATE and PGND
adds up to C_rss.
Power Dissipation/Junction Temperature
During normal operation, the MAX15009/MAX15011
have two main sources of internal power dissipation:
the LDO and the switched output.
The internal power dissipation due to the LDO can be
calculated as:
P_LDO = (V_IN − V_{OUT_LDO}) × (I_{OUT_LDO} + I_{OUT_SW})
where V_IN is the LDO input supply voltage in volts,
V_{OUT_LDO} is the output voltage of the LDO in volts,
I_{OUT_LDO} is the LDO total load current in mA, and
I_{OUT_SW} is the switch load current in mA.
Calculate the power dissipation due to the switch as:
P_SW = ΔV_SW × I_{OUT _ SW}
where ΔV_SW is the switch dropout voltage in volts for
the given I_{OUT_SW} current in mA.
The total power dissipation P_DISS in mW as:
P_DISS = P_LDO + P_SW
For prolonged exposure to overvoltage events, use the
V_IN voltage expected during overvoltage conditions.
Under these circumstances the corresponding internal
power dissipation contribution, P_OVP, calculated in the
previous section should also be included in the total
power dissipation, P_DISS.
For a given ambient temperature, T_A, calculate the
junction temperature, T_J, as follows:
T_J = T_A + P_DISS x θ_JA
where T_J and T_A are in °C and θ_JA is the junction-to-
ambient thermal resistance in °C/W as listed in the
Absolute Maximum Ratings section.
The junction temperature should never exceed +150°C
during normal operation.
Thermal Protection
When the junction temperature exceeds T_J = +160°C,
the MAX15009/MAX15011 shut down to allow the
device to cool. When the junction temperature drops to
+140°C, the thermal sensor turns all enabled blocks on
again, resulting in a cycled output during continuous
thermal-overload conditions. Thermal protection pro-
tects the MAX15009/MAX15011 from excessive power
dissipation. For continuous operation, do not exceed
the absolute maximum junction temperature rating of
+150°C.
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