| 摘要 |
A switching regulator (20) including an on-chip power output function (24) and also an interface (26) to which off-chip power output devices (42PU, 42PD) may be connected is disclosed. The switching regulator (20) includes an output enable circuit (25, 125) that senses the presence of external components at one of the terminals (T_PD, TL) of the on-chip power output function (24) or of the interface (26) to determine which of the output functions to enable. In one disclosed embodiment, the output enable circuit (25) detects whether an off-chip power transistor (T_PD) is connected at the interface (26), by charging a passive circuit (R1, C1) and determining whether the charging time constant is affected by the gate capacitance of the external transistor (42PD). In another disclosed embodiment, the output enable circuit (125) detects whether a load (30L) is connected to the output of the on-chip power output function (24) by measuring the voltage across a resistor (R1), into which a mirrored current is sourced, based on a current applied to the external terminal (TL); if the load (30L) is present, the voltage across the resistor (R1) will cause a logic transition to enable the on-chip power output function (24).
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