Balanced Technology Extended (BTX) Interface
PS_ON#
PS_ON# is an active low, TTL compatible signal that allows the motherboard to enable the three main system power supply DC output rails (+3.3VDC, +5VDC, +12VDC). PS_ON# is pulled up to +5VSB via a 10 kΩ resistor internal to the system power supply.
When PS_ON# is pulled to TTL low, the DC outputs are enabled by the system power supply.
When PS_ON# is held to TTL high by the motherboard or left open circuited, the system power supply shall not deliver current at the main DC outputs and shall hold them at zero potential with respect to ground.
Table 4-2. PS_ON# Signal Characteristics
Category | Minimum | Maximum |
VIL, Input Low Voltage | 0.1 V | 0.8V |
IIL, Input Low Current, Vin = 0.4 V | -1.6 mA | |
VIH, Input High Voltage, Iin = -200 µA | 2.0 V | |
VIH open circuit, Iin = 0 | 5.25 V |