Vicor PI2001-EVAL1 Active ORing Evaluation Board - Manual (Page 6)

Picor Corporation • www.picorpower.com P12001-EVAL1 User Guide Rev 1.1 Page 6 of 11
3.0 Blanking timer setup:
3.1 The blanking timer provides noise filtering for
typical switching power conversion that might
cause premature reverse current detection by
masking the reverse fault condition. The shortest
blanking time is 50 ns when the BK pin is
connected to ground. Connecting an external
resistor (R
BK , reference designators R7 for U1 and
R14 for U2) between the BK pin and ground will
increase the blanking time as shown in Figure 5.
Where: R
BK ≤ 200 KΩ
Note: When BK is connected to VC for slave mode .
operation,then the blanking time will be 270 ns typically.
4.0 Auxiliary Power Supply (Vaux):
4.1 The PI2001 Controller has a separate input (VC) that
provides power to the control circuitry and the gate
driver. An internal voltage regulator (VC) clamps the
VC voltage to 15.5 V typically.
4.2 Connect independent power source to Vaux inputs of
PI2001-EVAL1 Evaluation Board to supply power to
the VC input. The Vaux voltage should be 5V higher
than Vin (redundant power source output voltage) to
fully enhance the MOSFET. If the MOSFET is replaced
with different MOSFET, make sure that Vaux= Vin +
0.5 V + required voltage to be enhance the MOSFET.
4.3 10 Ω bias resistors (Rbias, reference designators R3
and R10) are installed on the PI2001-EVAL1 between
each Vaux input and VC pin of one of the PI2001
controller.
4.4 If Vaux is higher than the Clamp voltage, 15.5 V
typical, the Rbias value has to be changed using the
following equations:
4.4.1 Select the value of Rbias using the following
equation:
Rbias =
Vaux min – VC clampMAX
IC max
4.4.2 Calculate Rbias maximum power dissipation:
Pd Rbias =
(Vaux max – VC clampMIN ) 2
Rbias
Where:
Vaux
min
: Vaux minimum voltage
Vaux max : Vaux maximum voltage
VC ClampMAX : Maximum controller
clamp voltage, 16.0 V
VC ClampMIN : Minimum controller
clamp voltage, 14.0 V
IC max : Controller maximum bias current,
use 4.2 mA
4.4.3 For example, if the minimum Vaux = 22 V
and the maximum Vaux = 28 V
Rbias =
Vaux min – VC clampMAX
=
22 V–16 V
= 1.429 KΩ
IC max 4.2 mA
, use 1.43 KΩ 1% resistor
Pd Rbias = (Vaux max – VC clampMIN ) 2 = (28 V–14.0 V) 2 =137 mW
Rbias 1.43 KΩ
Note: Minimize the resistor value for low Vaux voltage
levels to avoid a voltage drop that may reduce the VC
voltage lower than required to drive the gate of the
internal MOSFET.
Figure 5 –BK Resistor selection versus Blanking Time