PI2007 Datasheet, PDF (10/19 Pages) Vicor Corporation – Universal High Side Active ORing Controller IC

Select the resistor (R_PG) value at the minimum input
voltage to avoid a voltage drop that may reduce V_VC-
SGND ^{lower than VC under voltage lockout.}
Select the value of R_PG using the following equations:
R_PG
 ^{VVCmin VVCCLMMax}
I_{VC _ Max}  0.1mA
R_PG maximum power dissipation:
PdR _PG

(V_{VC  max}
V_{VCCLMMin} ) ²
R_PG
Where:
V_VCmin : VC pin minimum applied voltage with
respect to Vin return
V_VCmax : VC pin maximum applied voltage with
respect to Vin return
V_{VCCLMMax} : Controller maximum clamp voltage, 12.5V
V : _{VCCLMMin} Controller minimum clamp voltage, 11.0V
I_{VC _ Max} : Controller maximum bias current, use
2.0mA plus 0.1mA for margin
Example: 40V <V_VC <50V
R_PG
 ^{VVC min  VVCCLMMax}
I_{VC _ Max}  0.1mA

40V  12.5V
2.1mA
 13.1k
  _PdRPG

(V_{VC max}
 V_{VC CLMMin} )²
R_PG

50V  11V
13.1k
2
 116mW
Alternative Bias Circuit with Device Enable:
Constant current circuit
In a wide operating input voltage range the size of R_PG
may be become large to support power dissipation. A
simple constant current circuit can be used instead of
R_PG to reduce power dissipation and can be used as a
device enable.
As shown in Figure 14, the constant current circuit
consists of an NPN transistor (Q2), Zener diode D_Z,
current limit resistor (R_LIMIT) and Zener bias resistor
(R_Z). R_LIMIT and R_Z can be very low power resistors
and Q2 is a signal transistor where its Collector-
Emitter Voltage (V_CEO) is equal or greater than the
input operating voltage and supports 2.5mA at the
operating input voltage.

Figure 14: Constant current bias circuit
Pulling the Q2 base (EN) to the system return (RTN)
will turn off the transistor and the controller returns
(SGND pin and PGND pin) will float and eventually
the MOSFET will be turned off. An open collector
device can be used to enable and disable the PI2007.
The constant current circuit should guarantee current
greater than the PI2007 maximum Quiescent current
(I_VC), 2.0mA.
R_LIMIT can be calculated from the following equation:
R_LIMIT
 ^{VZ _ MIN  VBE (on)}
I_{VC _ MAX}
Where:
V_{Z _ MIN} : Minimum Zener diode voltage
V_BE (on) : Q2 Base-Emitter On maximum voltage, for
default use V_BE (on) =0.7V
I_{VC _ MAX} : PI2007 Quiescent Current, maximum
I_VC=2.0mA
Zener Diode Selection:
Select a Zener diode with a low reverse current
requirement to minimize R_Z. Zener diodes with higher
break down voltage will have lower reverse current
and reduce Q2 collector current variation. Zener
diodes with a breakdown voltage of 6V and higher will
require low bias current and accurate voltage
breakdown.
R_Z maximum value can be calculated with the
following equation:
Note that the surface mount resistors have limited
operating voltage capability. Be sure to pick a
resistor package that can meet the maximum
operating voltage (Vin).
Picor Corporation • picorpower.com
PI2007
Rev 1.3
Page 10 of 19