PI2123 datasheet(7/20 Pages) VICOR

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Forward Voltage Comparator: FWD

The FWD comparator detects when a forward

current condition exists and SP is 6mV positive with

respect to SN. When SP-SN is less than 6mV, the

FWD comparator will assert the Fault flag to report a

fault condition indicative of a light load or “load not

present” condition or possible shorted MOSFET.

Forward Over Current Comparator: FOC

The FOC comparator indicates an excessive forward

current condition when SP is 66mV (typical) higher

than SN. When the FET is in the on-state and SP-

SN is higher than 66mV (typical) the PI2123 will

initiate a fault condition via the FT pin.

Slave:

In high current applications that exceed the single

PI2123 current handling capability, multiple PI2123’s

can be paralleled and synchronized by using the

slave function.

The Slave function synchronizes multiple PI2123’s

together and allows for localized control of each

paralleled MOSFET. One PI2123 will be designated

as the master and it will control the response of the

slaved PI2123’s.

When the PI2123 is configured in the “Master Mode”

by connecting the BK to ground, the SL will be an

output having the same signal characteristics as the

internal Gate Driver.

In this configuration, the

SL output is capable of driving up to ten PI2123’s,

configured

“Slave

Mode”,

through

their

corresponding SL pins. Logic high for the SL pin is

limited to 5.5V (max).

When the BK pin is tied to VC, the PI2123 becomes

a slave and the SL pin will be an input. The internal

Gate driver section and reverse current section are

the only active circuits in the slaved PI2123 while the

master performs the diagnostics and gate drive

control.

VC and Internal Voltage Regulator:

The PI2123 has a separate input (VC) to provides

power to the controller circuitry and the internal gate

driver. An internal regulator clamps the VC voltage

to 15.5V.

For high side applications, the VC input should be at

least 6V above the bus voltage (Vin) to properly

enhance the internal N-channel MOSFET.

The internal regulator circuit has a comparator to

monitor the 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 resistor divider to

monitor the input voltage.

The UV comparator

initiates a fault condition and pulls the FT pin low,

when UV falls below the Under-Voltage Falling

Threshold. If the PI2123 is configured in a floating

application, where the GND pin is connected to the

input voltage, the UV pin cannot detect the input

voltage. In this case, the UV pin should be disabled

by connecting it to the VC pin.

OV:

The Over-Voltage (OV) input trip point can be

programmed through an external resistor divider to

monitor the input voltage.

The OV comparator

initiates a fault condition and pulls the FT pin low

when OV rises above the Over-Voltage Rising

Threshold. If the PI2123 is configured in a floating

application, where the GND pin is connected to the

input voltage, the OV pin cannot detect the input

voltage. In this case, the OV pin should be disabled

by connecting it to the control GND pin.

Over-Temperature Detection:

The internal Over-Temperature block monitors the

junction temperature of the controller. The over-

temperature threshold is set to 160

°C with -10°C of

hysteresis.

When the controller temperature

exceeds this threshold, the over-temperature circuit

initiates a fault condition and pulls the FT pin low.

Fault:

The fault circuit output is an open collector with 40μs

delay to prevent any false triggering. The FT pin

will be pulled low when any of the following faults

occur:

•

Reverse Current

•

Forward Over-Current

•

Forward Low Current

•

Over-Temperature

•

Input Under-Voltage

•

Input Over-Voltage

•

VC pin Under-Voltage

A gate voltage detector prevents FOC or FWD from

initiating a fault when the MOSFET is in an OFF

condition.

The only fault condition that initiates gate turn-off of

the MOSFET (as well as a fault flag signal) is when

the reverse current fault conditions are met. All other

fault conditions issue only a fault flag signal via the

Picor Corporation • picorpower.com

PI2123

Rev 1.0

Page 7 of 20

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