Rainbow Electronics MAX15011 - Manual (Page 19)

where V SOURCE = (V OV x 0.04) + V 2 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:
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:
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.
P V I
SW SW
= × Δ
OUT SW _
P (V V ) (I I )
IN OUT_LDO OUT_LDO OUT_SW LDO
= − × +
MAX15009/MAX15011
Automotive 300mA LDO Regulators with
Switched Output and Overvoltage Protector
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