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PDF PI2126 Data sheet ( Hoja de datos )
| Número de pieza | PI2126 | |
| Descripción | 12 Amp Full-Function Active ORing Solution | |
| Fabricantes | Picor | |
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PI2126
Series
30 Volt, 12 Amp Full-Function Active ORing Solution
Description
The PI2126 is a complete full-function
Active ORing solution with a high-speed ORing MOSFET
controller and a very low on-state resistance MOSFET
designed for use in 12V Bus redundant power system
architectures. The PI2126 Cool-ORing solution is offered
in an extremely small, thermally enhanced 5mm x 7mm
LGA package and can be used in high side Active ORing
applications. The PI2126 enables extremely low power
loss with fast dynamic response to fault conditions,
critical for high availability systems.
The PI2126, with its 4.5mΩ internal MOSFET provides
very high efficiency and low power loss during steady
state operation. The PI2126 monitors the current
direction in the MOSFET and will respond very fast to a
reverse current due to input power source fault
condition to prevent undesired high current build-up in
the system. The PI2126 provides an active low fault flag
output to the system during reverse current, excessive
forward over-current and UVLO fault conditions.
Features
Integrated High Performance 12A, 4.5mΩ MOSFET
Very small, high density fully-optimized solution with
simple PCB layout
Fast dynamic response to power source failures,
with 90ns reverse current turn-off delay time
Accurate sensing capability to indicate system fault
conditions (-6mV reverse threshold)
Internal charge pump
Fault Status output
Applications
N+1 Redundant Power Systems
Servers & High End Computing
Telecom Systems
High-side Active ORing
Package Information
The PI2126 is offered in the following package:
25-pin 5mm x 7mm thermally enhanced LGA
package, achieving <11°C/W RθJ-PCB
Typical Application:
Vin1
S
D
SP PI2126
VR
VC
SN
FT FT
Vin2
S
D
SP PI2126
VR
VC
SN
FT FT
Figure 1: PI2126 High Side Active ORing
Picor Corporation • picorpower.com
Applied Input Short
Normal operation
0A
Input
Current
Reverse Current
Reverse detection
V(D) Redundant Bus
V(S) (Input)
MOSFET Turn Off Time
90ns
0V
Figure 2: PI2126 response time to an input short fault
condition
PI2126
Rev 1.1
Page 1 of 15
1 page  
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Functional Description:
The PI2126 integrated Cool-ORing product takes
advantage of two different technologies combining a
4.5m on-state resistance (RDS(on)) N-channel MOSFET
with high density control circuitry. This combination
provides superior density, minimizing PCB space to
achieve an ideal ORing diode function, significantly
reducing power dissipation and eliminating the need for
heat sinking, while minimizing design complexity.
The PI2126’s 4.5mΩ on-state resistance MOSFET used in
the conduction path enables a dramatic reduction in
power dissipation versus the performance of a diode
used in conventional ORing applications due to its high
forward voltage drop.
Due to the inherent characteristics of the MOSFET, while
the gate remains enhanced above the gate threshold
voltage it will allow current to flow in the forward and
reverse directions. Ideal ORing applications do not allow
for reverse current flow, so the controller has to be
capable of very fast and accurate detection of reverse
current caused by input power source failures, and turn
off the gate of the MOSFET as quickly as possible. Once
the gate voltage falls below the gate threshold, the
MOSFET is off and the body diode will be reverse biased
preventing reverse current flow and subsequent
excessive voltage droop on the redundant bus.
Differential Amplifier:
The PI2126 integrates a high-speed low offset voltage
differential amplifier to sense the difference between the
Sense Positive (SP) pin voltage and Sense Negative (SN)
pin voltage with high accuracy. The amplifier output is
connected to the Reverse and Forward comparators.
Reverse Current Comparator: RVS
The reverse current comparator provides the critical
function in the controller, detecting negative voltage
caused by reverse current. When the SN pin is 6mV
higher than the SP pin, the reverse comparator will force
the gate discharge circuit to turn off the MOSFET in
typically 90ns and assert the Fault ( ) low with a typical
delay of 8μs to report a fault condition.
The reverse comparator will hold the gate low until the
SP pin is 6mV higher than the SN pin. Reverse
comparator hysteresis is shown in Figure 3.
Figure 3: Reverse comparator hysteresis, the hysteresis
voltage is SP-SN
Forward Voltage Comparator: FWD
The FWD comparator detects when a forward voltage
condition exists and SP is above 275mV (typical) positive
with respect to SN. When SP-SN is more than 275mV, the
FWD comparator will assert the Fault ( ) low to report a
fault condition.
VC and Internal Voltage Regulator:
The PI2126 has a separate input VC that provides power
to the control circuitry. An internal regulator clamps the
VC voltage with respect to PG pin (VVC-PG) to 11.7V
typical.
The internal regulator circuit has a comparator to
monitor VC voltage and pulls the MOSFET Gate low when
VC is lower than the VC Under-Voltage Threshold.
The VR input pin can be connected to the input voltage
eliminating the need for an external limiter in 12V Bus
applications (10V to 14V). An internal 420Ω resistor is
connected between the VR pin and the internal regulator
VC pin.
Fault Indication:
The pin is an open collector NPN that will be pulled
low under the following fault conditions.
Typical Condition
1 Reverse: VSP-VSN ≤ -6mV
2 Forward: VSP-VSN ≥ +275mV
3 Forward VSP-VSN ≤ +6mV
4 UVLO
4.5V < VVC-PG <7.15V
Indication of possible faults
Input supply shorted
(MOSFET turned OFF)
Open FET, Gate short or
open, High current
(MOSFET turned ON)
Shorted FET on power-up
(MOSFET turned OFF)
Controller not ready
(MOSFET turned OFF)
Picor Corporation • picorpower.com
PI2126
Rev 1.1
Page 5 of 15
5 Page 
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the load through the MOSFET. Depending on the output
impedance of the system and the parasitic inductance, the
reverse current in the MOSFET may exceed the source
pulsed current rating (60A) before the PI2126 MOSFET is
turned off.
The peak current during an input short condition is
calculated as follows, assuming that the output has very
low impedance and it is not a limiting factor:
Where:
: Peak current in PI2126 MOSFET before it is
turned off.
: Input voltage or load voltage at S pin before
input short condition did occur.
: Reverse fault to MOSFET turn-off time.
: Circuit parasitic inductance
The high peak current during an input short stores energy
in the circuit parasitic inductance, and as soon as the
MOSFET turns off, the stored energy will be released and
this will produce a high negative voltage and ringing at the
MOSFET source. At the same time the energy stored at the
drain side of the internal MOSFET will be released and
produce a voltage higher than the load voltage. This event
will create a high voltage difference between the drain and
source of the MOSFET. The MOSFET may avalanche, but
this avalanche will not affect the MOSFET performance
because the PI2126 has a fast response time to the input
fault condition and the stored energy will be well below
the MOSFET avalanche capability.
MOSFET avalanche during input short is calculated as
follows:
Where:
: Avalanche energy
: MOSFET breakdown voltage (30V)
Power dissipation:
In Active ORing circuits the MOSFET is always on in steady
state operation and the power dissipation is derived from
the total source current and the on-state resistance of the
MOSFET.
The PI2126 internal MOSFET power dissipation can be
calculated with the following equation:
Where:
: MOSFET power dissipation
: Source Current
: MOSFET on-state resistance
Note: For the worst case condition, calculate with
maximum rated RDS(on) at the MOSFET maximum operating
junction temperature because RDS(on) value is directly
proportional to temperature. Refer to Figure 10 for
normalized RDS(on) values over temperature. The PI2126
maximum RDS(on) at 25°C is 6mΩ and will increase by 40% at
125°C junction temperature.
The Junction Temperature rise is a function of power
dissipation and thermal resistance.
Where:
: Junction-to-Ambient thermal resistance, 46°C/W
This may require iteration to get to the final junction
temperature. Figure 13 and Figure 14 show the PI2126
internal MOSFET final junction temperature curves versus
conducted current at maximum RDS(on), given ambient
temperatures and air flow.
Picor Corporation • picorpower.com
PI2126
Rev 1.1
Page 11 of 15
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet PI2126.PDF ] | |
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