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ADP1046A View Datasheet(PDF) - Analog Devices

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ADP1046A Datasheet PDF : 88 Pages
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Data Sheet
OrFET Operation Examples
Hot Plug into a Live Bus
A new PSU is plugged into a live 12 V bus (yellow). The internal
voltage, VS1 (red), is ramped up before the OrFET is turned on.
After the OrFET is turned on (green), current in the new PSU
begins to flow to the load (blue). The turn-on voltage threshold
between the new PSU and the bus is programmable.
VS3
VS1
OrFET
4
CS2
3
2
CH1 2.00V CH2 2.00V
CH3 2.00A CH4 10.0V
M10.0ms
A CH4 100mV
Figure 27. Hot Plug into a Live Bus (Yellow Is Bus Voltage; Red Is VS1 Voltage;
Green Is OrFET Control Signal; Blue Is Load Current)
Runaway Master
A rogue PSU on the bus (yellow) has a fault condition, causing
the bus voltage to increase above the OVP threshold. The good
PSU turns off the OrFET (green) and regulates its internal volt-
age, VS1 (red). When the rogue power supply fault condition is
removed, the bus voltage decreases. The OrFET of the good PSU
is immediately turned on, and the good PSU resumes regulating
from VS3±.
VS3
VS1
4
OrFET
CS2
3
CH1 2.00V CH2 2.00V
CH3 2.00A CH4 10.0V
M50.0ms
A CH4 0mV
Figure 28. Runaway Master (Yellow Is Bus Voltage; Red Is VS1 Voltage;
Green Is OrFET Control Signal; Blue Is Load Current)
ADP1046A
Short Circuit
When one of the output rectifiers fails, the bus voltage can
collapse if the OrFET is not promptly turned off. The fast OrFET
comparator is used to protect the system from this fault event.
Figure 29 shows a short circuit applied to the output capacitors
before the OrFET. After the fast OrFET threshold for CS2± (blue)
is triggered, the OrFET (green) is turned off. Figure 29 also shows
the operation when the short circuit is removed. The internal
regulation point, VS1 (red), returns to 12 V, and the OrFET
(green) is reenabled. The PSU again begins to contribute
current to the load (blue).
VS3
OrFET
4
CS2
3
VS1
CH1 2.00V CH2 2.00V
CH3 2.00A CH4 10.0V
M200.0ms
A CH4 7.5mV
Figure 29. Internal Short Circuit (Yellow Is Bus Voltage; Red Is VS1 Voltage;
Green Is OrFET Control Signal; Blue Is Load Current)
Light Load Mode Operation
PSU 1 increases its voltage at light load from 12 V to 12.1 V
(yellow). Both PSU 1 and PSU 2 are CCM; therefore PSU 1
sources current and PSU 2 sinks current (blue). In PSU 2, the
OrFET control turns off the OrFET to prevent reverse current
from flowing. Note that the OrFET voltage (green) is solid during
this transition because PSU 1 and PSU 2 are in CCM mode.
VS1
VS3
4
OrFET
3
CS2
CH1 2.00V CH2 2.00V
CH3 2.00A CH4 10.0V
M5.0ms
A CH4 8.3mV
Figure 30. Light Load Mode (Yellow Is Bus Voltage; Red Is VS1 Voltage;
Green Is OrFET Control Signal; Blue Is Load Current)
Rev. 0 | Page 23 of 88
 

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