PI2007 Datasheet, PDF (15/19 Pages) Vicor Corporation – Universal High Side Active ORing Controller IC

VC bias through Constant current circuit
Select an NPN transistor with V_CEO equal or higher
than the input voltage (Vin) plus any expected
transient voltage and capable of handling the
expected maximum power dissipation. Any NPN
transistor with V_CEO ≥ 100V in a small footprint is
suitable. An exemplary NPN is FJV1845 from
Fairchild:
From the FJV1845 datasheet:
NPN Silicon Transistor
V_CEO= 120V Collector-Emitter maximum voltage
I_C = 50mA maximum collector current
h_FE = 150 minimum at I_C=3mA
V_BE(sat)= 0.55V to 0.65V Base-Emitter saturation
voltage at 25°C
Select Zener Diode: Select the Zener diode with low
bias current, a Zener diode with V_Z=10 in small foot
print is suitable for this application. An exemplary
Zener diode MM3Z10VST1 from ON Semiconductor
From the MM3Z10VST1 datasheet:
10V, 200mW Zener Diode
V_Z= 9.80V to 10.2V Zener voltage range
I_R = 10μA will hold the Zener breakdown voltage
at 9.8V
R_LIMIT
 ^{VZ _ MIN VBE (on)}  ^{9.8V  0.7V}
I_{VC _ MAX}
2.1mA
 4.33k
Or 4.32kΩ 1%
I _{B _ MAX}
 ^{I C _ MAX}
h_{FE _ MIN}
 ^3.5mA  23.33A
150
R_Z Calculation:
Use 100μA as minimum for the Zener diode reverse
leakage current and Q2 base current combined.
R_Z
 ^{Vin _ MIN  VZ _ MAX}
I _Z  I _{B _ MAX}
 ^{36V  10.2V}
100A
 258k
Select R_Z= 249kΩ 1%
Maximum Q2 collector current:
I _{C _ MAX}
 ^{VZ _ MAX  VBE _ MIN}
R_{LIMIT _ MIN}
 ^{10.2V  0.50V}
4.32k * 0.98
 2.29mA
Maximum Q2 power dissipation
Pd _Q2  I _{C _ MAX}  [Vin_MAX  V_VCCLM  (V_{Z _ MIN}  V_{EB _ MAX} )]

Pd _Q2  2.29mA[60V 11V  (9.8V  0.7V )]  91.37mW
The transistor Power De-rating vs. temperature curve
in the manufacturer datasheet shows that the device
can operate up to 110°C.
Figure 18: PI2007 in high side +48V application, VC
is biased through constant current circuit.
Fault Indication:
PI2007 SGND pin in this application is floating and
FT is referenced to SGND. The FT output can be
referenced to system return (RTN) by adding a level
shift circuit as shown in Figure 19.
Q1: 2SA1579T106R, 120V PNP transistor from
Rohm.
Q2: DTC114EET1G, 50V NPN with bias resistors from
ON semiconductor.
D1: 30V general purpose diode.
Figure 19: FT level shift circuitry
Picor Corporation • picorpower.com
PI2007
Rev 1.3
Page 15 of 19