Seasonic Connect 750 W Review - The Solution for Cable Management 15

Seasonic Connect 750 W Review - The Solution for Cable Management

Transient Response & Inrush Current »

Hold Up Time

Hold Up Time represents the duration, a PSU can maintain stable output as defined by the ATX specification without input power. This is very important when the quality of your electricity varies, and there are short drops in the supply (dips or brown outs).

In the oscilloscope screenshots below, the blue line is the AC input mains signal, the green line the "Power Good" signal, and the yellow line the +12V rail. The measured timing variable is listed as ΔX.

Hold Up Time





AC Loss To PWR_OK Hold Up Time





PWR_OK Inactive to DC Loss Delay





As expected after seeing the huge bulk cap, hold-up time is long. The power ok signal is also accurate, with a pretty long DC Loss delay.

Timings for Alternative Sleep Mode (ASM)

Traditionally, sleep mode (S3) shuts the system off for a long time (minutes or hours) to reduce power consumption. However, this approach adds a few seconds delay when resuming from standby. Microsoft recently introduced Modern Sleep, which brings the instant-on capability to PCs—just like your phone instantly turns on without any noticeable delay. Modern Sleep builds on the Alternative Sleep Mode capability, which Intel has defined. To support ASM, a power supply must wake up from sleep quickly to ensure system stability—think of it as the PSU's boot time.

Source: Intel
Timings for Alternative Sleep Mode
ParameterDescriptionRecommended Value
T0AC power on time< 2s
T1Power-on time< 150 ms
T2Rise time0.2 - 20 ms
T3PWR_OK delay100 - 150 ms
T4PWR_OK rise time< 10 ms
T5AC loss to PWR_OK hold-up time> 16 ms
T6PWR_OK inactive to DC loss delay> 1 ms
For the reviewed PSU we measured T1 and T3 at 20% and 100% Load.

T1 (Power-on time) & T3 (PWR_OK delay)
LoadT1T3
20%78 ms314 ms
100%90 ms314 ms



The PWR_OK delay is way out of the 100–150 ms range, so this PSU is not compatible with alternative sleep mode.
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