PI2126 Datasheet, PDF (10/15 Pages) Vicor Corporation – 30 Volt, 12 Amp Full-Function Active ORing Solution

EOL
Application Information
The PI2126 is designed to replace high side ORing diodes in
high current low voltage bus redundant power
architectures. Replacing a traditional diode with a PI2126
will result in significant power dissipation reduction as well
as board space reduction, efficiency improvement and
additional protection features.
This section describes in detail the procedure to follow
when designing with the PI2126 Active ORing solution.
Control Circuitry Bias:
The PI2126 control circuitry and the gate driver for the
internal MOSFET are biased through the VC pin or VR pin.
An internal regulator clamps the VC voltage (V_VC-PG) to
11.7V typically. An internal bypass ceramic capacitor
(0.1μF) is connected between VC and PG to hold V_VC-PG
steady.
In 12V system applications, where the input voltage (Vin) is
between 10V and 14V, connect the VR pin to Vin and
connect PG to the Vin return, Figure 1. A 420Ω internal
resistor (R_Bias) is connected between the VR pin and the VC
pin.
In high voltage applications above 14V, PG pin has to float
above ground and VC pin will be connected directly to Vin.
As shown in Figure 17, VR pin is disconnected and PG pin
float on a bias resistor (R_PG). A low current low forward
voltage drop Schottky diode is required for the PI2126
when PI2126 is configured floating on PG. Connect one
terminal of R_PG to the PG pin and the other end of R_PG to
ground (Vin return). Connect the Schottky diode anode to
the PG pin and connect its cathode to the VC pin.
Vin1
S
SP
VR
VC
D1
PMEG3005AEA
PI2126
RPG
D
SN
FT FT
R_PG selection for input voltage greater than 14V:
Select the resistor (R_PG) value at the minimum input
voltage to avoid a voltage drop that may reduce V_VC-PG
lower than VC under voltage lockout.
Select the value of R_PG using the following equations:
And R_PG maximum power dissipation is:
Where:
: Minimum applied input voltage
: Maximum applied input voltage
: Controller maximum Under-Voltage Rising
Threshold, 8.5V
: Controller maximum clamp voltage, 12.5V
: Controller maximum bias current, use 2.0mA
: 0.1mA is added for margin
R_PG calculation example
Vin (minimum) = 11V and Vin (maximum) = 18V
Select a lower typical resistor value (1KΩ) and calculate its
power dissipation.
Vin2
S
SP
VR
VC
D1
PMEG3005AEA
PI2126
RPG
D
SN
FT FT
Figure 17: PI2126 in application above 14V
Recommended Schottky Diode:
PMEG3005AEA: from NXP or equivalent
Picor Corporation • picorpower.com
Internal N-Channel MOSFET BV_DSS:
The PI2126’s internal N-Channel MOSFET breakdown
voltage (BV_DSS) is rated for 30V at 25°C and will degrade to
28V at -40°C, refer to Figure 8. Drain to source voltage
should not exceed B_VDSS in nominal operation. During a
fast switching transient the MOSFET can tolerate voltages
higher than its B_VDSS rating under avalanche conditions,
refer to the Absolute Maximum Ratings table.
In Active ORing applications when one of the input power
sources is shorted, a large reverse current is sourced from
PI2126
Rev 1.1
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