Intel 0.9 Manual Do Utilizador
Intel ATX Power Supply Design Guide
Version 0.9
Page
17
3.4.2 PS_ON#
PS_ON# is an active-low, TTL-compatible signal that allows a motherboard to remotely
control the power supply in conjunction with features such as soft on/off, wake-on-LAN, or
wake-on-modem. When PS_ON# is pulled to TTL low, the power supply should turn on
the five main DC output rails: +12VDC, +5VDC, +3.3VDC, -5VDC, and -12VDC. When
PS_ON# is pulled to TTL high or open circuited, the DC output rails should not deliver
current and should be held at zero potential with respect to ground. PS_ON# has no effect
on the +5VSB output, which is always enabled whenever the AC power is present.
control the power supply in conjunction with features such as soft on/off, wake-on-LAN, or
wake-on-modem. When PS_ON# is pulled to TTL low, the power supply should turn on
the five main DC output rails: +12VDC, +5VDC, +3.3VDC, -5VDC, and -12VDC. When
PS_ON# is pulled to TTL high or open circuited, the DC output rails should not deliver
current and should be held at zero potential with respect to ground. PS_ON# has no effect
on the +5VSB output, which is always enabled whenever the AC power is present.
The power supply shall provide an internal pull-up to TTL high. The power supply shall
also provide debounce circuitry on PS_ON# to prevent it from oscillating on/off at startup
due to activation by a mechanical switch. The DC output enable circuitry must be SELV-
compliant.
also provide debounce circuitry on PS_ON# to prevent it from oscillating on/off at startup
due to activation by a mechanical switch. The DC output enable circuitry must be SELV-
compliant.
Table 10: PS_ON# Signal Characteristics
Min.
Max.
V
IL
, Input Low Voltage
0.0 V
0.8 V
I
IL
, Input Low Current, Vin = 0.4 V
-1.6 mA
V
IH
, Input High Voltage, Iin = -200 µA
2.0 V
V
IH
open circuit, Iin = 0
5.25 V
3.4.3 +5VSB
+5VSB is a “standby” supply output that is active whenever the AC power is present. It
provides a power source for circuits that must remain operational when the five main DC
output rails are in a disabled state. Example uses include soft power control, wake-on-
LAN, wake-on-modem, intrusion detection, or suspend state activities. +5VSB is required
for the implementation of PS_ON#.
provides a power source for circuits that must remain operational when the five main DC
output rails are in a disabled state. Example uses include soft power control, wake-on-
LAN, wake-on-modem, intrusion detection, or suspend state activities. +5VSB is required
for the implementation of PS_ON#.
The +5VSB output should be capable of delivering a minimum of 720 mA at +5 V ±5% to
external circuits. Because trends indicate a growing demand for standby power, it is
recommended that a family of designs be created to supply 720 mA, 1.0 A, or 1.5 A to meet
various customer requirements. Overcurrent protection is required on the +5VSB output
regardless of the output current rating. This ensures the power supply will not be damaged
if external circuits draw more current than the supply can provide.
external circuits. Because trends indicate a growing demand for standby power, it is
recommended that a family of designs be created to supply 720 mA, 1.0 A, or 1.5 A to meet
various customer requirements. Overcurrent protection is required on the +5VSB output
regardless of the output current rating. This ensures the power supply will not be damaged
if external circuits draw more current than the supply can provide.
3.4.4 Power-on Time
The power-on time is defined as the time from when PS_ON# is pulled low to when the
+5VDC and +3.3VDC outputs are within the regulation ranges specified in Section 3.2.1.
The power-on time shall be less than 500 ms.
+5VDC and +3.3VDC outputs are within the regulation ranges specified in Section 3.2.1.
The power-on time shall be less than 500 ms.
+5VSB shall have a power-on time of 2 seconds maximum after application of valid AC
voltages.
voltages.