pip401 NXP Semiconductors, pip401 Datasheet - Page 10

• Manufacturer Part Number: pip401
• Description: Intelligent Switch 7-pin 6+tab D2pak
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 10578
Product data
11.2 Fault condition
of line inductance. The VRS connection may be connected directly to VO if the circuit
inductance is negligible. In general, this means that the distance between the PIP401
and the load must be less than 25 mm.
Assume that the 12 V supply to V
condition, with no voltage between input and output, both PIP401 devices will be off.
If one of the 5 V supplies is turned on, the comparator output in the associated
PIP401 will go HIGH, slowly turning on the series power switch (soft start). The series
power switch in the other PIP401 will remain off, preventing current from flowing from
output to input.
If both 5 V supplies are on, and the power supplies have forced current sharing
capability, then both PIP401 devices will be on.
If the power supplies do not have forced current sharing capability then the supply
with the highest output voltage will tend to supply all the load current. If the difference
in output voltage is greater than a few millivolts, then the PIP401 device connected to
the power supply with the highest output voltage will be on, and the PIP401 device
connected to the power supply with the lowest output voltage will be off.
Remote voltage sensing is not usually a feature of this topology of parallel redundant
operation. This is because the remote sense lines provide an alternative path for fault
currents when one of the power supplies fails. Therefore, in order to maintain good
load regulation, the PIP401 must have a low forward voltage drop under normal
operating conditions. The typical on-state voltage drop of the PIP401 is 70 mV at
40 A. Two or more PIP401 devices may be connected in parallel in order to reduce
this further.
With reference to
current to the load. Assume that one of the supplies fails and its output voltage
collapses to zero. The voltage on the output terminal of the PIP401 drops from 5 V to
zero and goes slightly negative as the voltage across the line inductance reverses in
order to maintain current flow.
At the instant that the power supply fails, the PIP401 detects that the voltage on VI is
less than the voltage on the remote sense connection VRS. The drive voltage to the
series power switch is immediately turned off, but the series power switch takes up to
a further 300 ns to switch off completely. During this delay time, the current
decreases from its initial value to zero at a rate determined by the bus voltage and the
line inductance.
If the PIP401 turns off completely before the current reaches zero, then there is no
reverse current flow. On the other hand, if the rate of fall of current is very high,
current will flow from VO to VI until the PIP401 turns off completely. The peak reverse
fault current depends on the magnitude of the line inductance and the initial load
current.
Rev. 03 — 5 November 2002
Figure
7, assume that both 5 V power supplies are supplying
CC
is present but both 5 V supplies are off. In this
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
OR-ing Intelligent Switch
PIP401
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