PI2001-EVAL1 datasheet(6/11 Pages) VICOR

6 / 11 page

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 (RBK, 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: RBK ≤ 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 =

Vauxmin –VCclampMAX

ICmax

4.4.2 Calculate Rbias maximum power dissipation:

PdRbias =

(Vauxmax –VCclampMIN)2

Rbias

Where:

Vauxmin: Vaux minimum voltage

Vauxmax: Vaux maximum voltage

VCClampMAX: Maximum controller

clamp voltage, 16.0 V

VCClampMIN: Minimum controller

clamp voltage, 14.0 V

ICmax: 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 =

Vauxmin –VCclampMAX

22 V–16 V

= 1.429 KΩ

ICmax

4.2 mA

use 1.43 KΩ 1% resistor

PdRbias = (Vauxmax –VCclampMIN)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

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