PI2007 Datasheet, PDF (14/19 Pages) Vicor Corporation – Universal High Side Active ORing Controller IC

Typical application Example 2:
Requirement:
+48V High Side Redundant
Bus Voltage = +48V (+36V to +60V, 100V for 100ms
transient)
Load Current = 5A load (assume through each
redundant path)
Maximum Ambient Temperature = 60°C
Solution:
A single PI2007 with a suitable MOSFET for each
redundant +48V power source should be used and
configured as shown in Figure 17 or Figure 18. Figure
17 is configured with the VC biased from the return
line through a bias resistor. Figure 18 is configured
with the VC biased from the return line through the
constant current circuit.
Select a suitable N-Channel MOSFET: Select the
N-Channel MOSFET with voltage rating higher than
the input voltage, Vin, plus any expected transient
voltages, with a low R_DS(on) that is capable of
supporting the full load current with margin. For
instance, a 100V rated MOSFET with 10A current
capability is suitable. An exemplary MOSFET having
these characteristic is IRF7853PbF from International
Rectifier.
From the IRF7853PbF datasheet:
N-Channel MOSFET
V_DS= 100V
I_D = 8.3A maximum continuous drain current at
25°C
I_D-PULSE = 66A pulsed drain current
VGS(MAX) = 20V
R_θJA= 50°C/W on 1in² copper, t ≤ 10seconds
R_θJA for continuous operation not provided
R_DS(on)=14.4mΩ typical at V_GS=10V, T_J=25°C
R_DS(on)=18mΩ maximum at V_GS=10V, T_J=25°C
Reverse current threshold is:
Is.reverse  ^Vth.reverse  ^{ 6mV}  333mA
R_{DS (on)}
18m
Power dissipation:
Rds(on) is 18mΩ maximum at 25°C & 10Vgs and will
increase as the temperature increases. Add 20°C to
maximum ambient temperature to compensate for the
temperature rise due to power dissipation. At 80°C
(60°C + 20°C) Rds(on) will increase by 40%.
R_DS(on)  18m 1.40  25.2m maximum at 80°C
Maximum Junction temperature
T_J
max

60C
  ^50C
^W
 (5.0A)²
 25.2m


91.5C
Recalculate maximum R_DS(on) at 95°C.
At 95°C Rds(on) will increase by 50%:

R_DS(on)  18m 1.50  27m maximum at 95°C
Maximum Junction temperature after 10s
T_J
max

60C
  ^50C
^W
 (5.0A)²
 27m


93.75C
For continuous operation refer the MOSFET
datasheet for R_θJA under continuous operation and
plug it in place of 50°C/W.
VC Bias: Since the bus voltage is higher than 14V,
connect VC pin to the high side of the input voltage
and connect a bias resistor (R_PG) or a constant current
circuit between PI2007 SGND pin and ground (Vin
return), as shown in Figure 17 and Figure 18. Place a
low forward voltage drop Schottky diode and a 1μF
ceramic capacitor between SGND pin and VC pin.
Also connect PGND pin to SGND at the coupling
capacitor terminal.
Recommended Schottky: PMEG3005AEA from NXP
or equivalent
R_PG selection:
R_PG
 ^{VVCmin  VVCCLMMax}
I_{VC _ Max}  0.1mA

36V  12.5V
2.0mA  0.1mA
 11.19k
Select R_PG=11kΩ 1%
R_PG maximum power dissipation:
  _PdRPG

(V_{VC  max}
V_{VCCLMMin} ) ²
R_PG

60V 11V
11k
2
 218mW
Use ¼ W Resistor in 1206 package
Figure 17: PI2007 in high side +48V application, VC
is biased through a bias resistor
Picor Corporation • picorpower.com
PI2007
Rev 1.3
Page 14 of 19