LP5951

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SNVS345G – JUNE 2006 – REVISED DECEMBER 2014

Feature Description (continued)

7.3.5 Thermal-Overload Protection

Thermal-Overload Protection limits the total power dissipation in the LP5951. When the junction temperature

exceeds TJ = 160°C typ., the shutdown logic is triggered and the PMOS is turned off, allowing the device to cool

down. After the junction temperature dropped by 20°C (temperature hysteresis), the PMOS is activated again.

This results in a pulsed output voltage during continuous thermal-overload conditions.

The Thermal-Overload Protection is designed to protect the LP5951 in the event of a fault condition. For normal,

continuous operation, do not exceed the absolute maximum junction temperature rating of TJ = 150°C (see

Absolute Maximum Ratings).

7.3.6 Reverse Current Path

The internal PFET pass device in LP5951 has an inherent parasitic body diode. During normal operation, the

input voltage is higher than the output voltage and the parasitic diode is reverse biased. However, if the output is

pulled above the input in an application, then current flows from the output to the input as the parasitic diode gets

forward biased. The output can be pulled above the input as long as the current in the parasitic diode is limited to

50 mA.

For currents above this limit an external Schottky diode must be connected from VOUT to VIN (cathode on VIN,

anode on VOUT).

7.4 Device Functional Modes

7.4.1 Enable (EN)

The EN pin voltage must be higher than the VIH threshold to ensure that the device is fully enabled under all

operating conditions. The EN pin voltage must be lower than the VIL threshold to ensure that the device is fully

disabled. However if the application does not require the shutdown feature, the VEN pin can be tied to VIN to

keep the regulator output permanently on.

7.4.2 Minimum Operating Input Voltage (VIN)

The LP5951 internal circuitry is not fully functional until VIN is at least 1.8 V. The output voltage is not regulated

until VIN ≥ (VOUT + VDO), or 1.8 V, whichever is higher.

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