7.3.1 High Input Operating Voltage

Unlike many other PNP low dropout regulators, the LM2936Q remains fully operational with V_IN = 40 V, and the LM2936QHBM remains fully operational with V_IN = 60 V. Owing to power dissipation characteristics of the available packages, full output current cannot be ensured for all combinations of ambient temperature and input voltage.

While the LM2936QHBM maintains regulation to 60 V, it does not withstand a short circuit to ground on the output when V_IN is above 40 V because of safe operating area limitations in the internal PNP pass device. Above 60 V the LM2936Q breaks down with catastrophic effects on the regulator and possibly the load as well. Do not use this device in a design where the input operating voltage may exceed 40 V, or where transients are likely to exceed 60 V.

7.3.2 Thermal Shutdown (T_SD)

The T_SD circuitry of the LM2936Q has been designed to protect the device against temporary thermal overload conditions. The T_SD circuitry is not intended to replace proper heat-sinking. Continuously running the LM2936Q device at T_SD may degrade device reliability as the junction temperature will be exceeding the absolute maximum junction temperature rating. If the LM2936Q goes into T_SD mode, the output current shuts off until the junction temperature falls approximately 10°C — the output current is then automatically restored. The LM2936Q continuously cycles in and out of T_SD until the condition is corrected. The LM2936Q T_SD junction temperature is typically 160°C.

7.3.3 Short-Circuit Current Limit

The output current limiting circuitry of the LM2936Q has been designed to limit the output current in cases where the load impedance is unusually low. This includes situations where the output may be shorted directly to ground. Continuous operation of the LM2936Q at the current limit typically results in the LM2936Q transitioning into T_SD mode.

7.3.4 Shutdown (SD) Pin

The 5-V LM2936QHBMA has a pin for shutting down the regulator output. Applying a logic level high (> 2 V) to the SD pin causes the output to turn off. Leaving the SD pin open, connecting it to ground, or applying a logic level low (< 0.6 V) allows the regulator output to turn on.