SSI
ERP2U Power Supply Design Guide, V2.31
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8 Control and Indicator Functions
The following sections define the input and output signals from the power supply.
Signals that can be defined as low true use the following convention:
signal# = low true
8.1 PSON#
STATUS
Required
The PSON# signal is required to remotely turn on/off the power supply. PSON# is an active low signal that turns
on the +3.3 V, +5 V, +12 V, and -12 V power rails. When this signal is not pulled low by the system, or left open,
the outputs (except the +5 VSB and Vbias) turn off. This signal is pulled to a standby voltage by a pull-up resistor
internal to the power supply. Refer to Figure 4 for timing diagram.
Table 29: PSON# Signal Characteristic
Signal Type
Accepts an open collector/drain input from the system.
Pull-up to VSB located in power supply.
PSON# = Low ON
PSON# = Open or High OFF
MIN MAX
Logic level low (power supply ON) 0 V 1.0 V
Logic level high (power supply OFF) 2.0 V 5.25 V
Source current, Vpson = low 4 mA
Power up delay: Tpson_on_delay 5 ms 400 ms
PWOK delay: T pson_pwok 50 ms
5.25V
≤ 1.0 V
PS is
enabled
≥ 2.0 V
PS is
disabled
1.0V 2.0V
Enabled
Disabled
Hysteresis ≥ 0.3V and/or other de-bounce method
0V
Figure 5: PSON# Signal Characteristics