PI2002 datasheet(7/23 Pages) VICOR

7 / 23 page

Picor Corporation • picorpower.com

PI2002

Rev1.1 Page 7 of 23

Figure 3: OCT Off time vs. OCT capacitor value

Short Circuit Detect: SCD

This comparator block input (for 10L-TDFN package

only) can be connected to the load directly or

programmed to a higher voltage with a resistor

divider. The SCD function allows the user to define

the (Hard Short) voltage level expected if a non-ideal

short circuit occurs at the load. To prevent damage

of the MOSFETs under this condition (VSCD<335mV)

the gate charge current (IG-SC) is increased by a

factor of approximately 5 times resulting in fast

charging of the MOSFET gates.

This feature

enables the capability to distinguish between a

faulted load versus powering capacitive and low

resistive loads without entering the OCT mode. This

pin can be grounded to provide a fast gate charging

or pulled to VC for lower gate current to drive highly

capacitive loads with resulting slow gate charge

under the fault condition. If the resulting temperature

rise of the MOSFETs is thermally coupled to the

controller, invoking a thermal shutdown, the thermal

time constant of the system will determine the

average duty cycle further protecting the MOSFETs.

The SCD pin is not available in the SO-8 package

version and is internally preset for slow gate charge,

where the Gate source current is 300µA.

VC and Internal Voltage Regulator:

The PI2002 has a separate input (VC) that provides

power to the control circuitry and the gate driver. An

internal regulator clamps the VC voltage to 15.5V.

For high side applications, the VC input should be

high enough above the bus voltage to properly

enhance the external N-channel MOSFETs.

The internal regulator circuit has a comparator to

monitor VC voltage and initiates a FAULT condition

when VC is lower than the VC Under-Voltage

Threshold.

UV:

The Under-Voltage (UV) input trip point can be

programmed through an external resistive divider to

monitor the input voltage.

The UV comparator

initiates a gate low condition turning the MOSFETs

off and initiates a fault condition pulling the

FT pin

low, when UV falls below the Under-Voltage Falling

Threshold.

OV:

The Overvoltage (OV) input trip point (for 10L-TDFN

package only) can be programmed through an

external resistive divider to monitor the input voltage.

The OV comparator initiates a fault condition and

pulls the

pin low when OV rises above the

Overvoltage Rising Threshold. The PI2002 will turn

the Gate output off if the OV and the Forward

Current conditions are both true. The low resistance

redundant paths of an Active ORing system tend to

force all the input sources to the same voltage

making it difficult to identify the noncompliant

source. By ANDing OV with the Forward Current

Threshold the noncompliant source is identified and

disconnected from the system.

The OV pin is not available in the SO-8 package

version and is disabled.

Over-Temperature Detection:

The internal Over-Temperature block monitors the

junction temperature of the controller. The Over-

Temperature threshold is set to 145

°C with -10°C of

hysteresis.

When the controller temperature

exceeds this threshold, the Over-Temperature circuit

pulls GATE pin low and initiates a fault condition and

pulls the FT pin low. By maintaining proper thermal

matching between the controller and the power

MOSFETs, this function can be used to protect the

MOSFETs from thermal runaway conditions.

Gate Driver:

The gate driver (GATE) output is configured to drive

external N-channel MOSFETs. In the high state, the

gate driver applies a current source that is

dependent on the SCD pin voltage. The controller

regulates the gate voltage to 10V above the SN pin

when the VC voltage is 10.5V higher than the SN

pin. Otherwise the gate voltage (VG) to VSN will be

{VG-SN = VC - VSN – 0.5V}. Note that VC is the

controller internal regulated voltage.

When a reverse current fault is initiated, the gate

driver pulls the GATE pin low and discharges the

FET gate with 4A peak capability.

PI2002 数据表(PDF) 7 Page - Vicor Corporation

PI2002 数据表(HTML) 7 Page - Vicor Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

数据表下载