PI2125-00-LGIZ 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 PI2125 will

initiate a fault condition via the FT pin.

Slave:

In high current applications that exceed the single

PI2125 current handling capability, multiple PI2125’s

can be paralleled and synchronized by using the

slave function.

The Slave function synchronizes multiple PI2125’s

together and allows for localized control of each

paralleled MOSFET. One PI2125 will be designated

as the master and it will control the response of the

slaved PI2125’s.

When the PI2125 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 PI2125’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 PI2125 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

PI2125 while the master performs the diagnostics

and gate drive control.

VC and Internal Voltage Regulator:

The PI2125 has a separate input (VC) that provides

power to the control 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. For bus

voltages higher than 10V (15.5V – 5.5V), the PI2125

should be floated to Vin as shown in Figure 23, and

a resister has to be added in series between Vaux

and VC. The required resister value calculation is

shown in the application section of this document.

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, when the PI2125 is used

ground

referenced

applications.

The

comparator initiates a fault condition and pulls the

pin low, when UV falls below the Under-

Voltage Falling Threshold. If the PI2125 is

configured in a floating application, where the GND

pin is connected to the input voltage, as shown in

Fig 23, 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, when the PI2125 is used

ground

referenced

applications.

The

comparator initiates a fault condition and pulls the

FT pin low when OV rises above the Over-Voltage

Rising Threshold. If the PI2125 is configured in a

floating application, where the GND pin is connected

to the input voltage, as shown in Fig 23, the OV pin

cannot detect the input voltage. In this case, the OV

pin should be disabled by connecting it to controller

ground 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

occurs:

•

Reverse Current

•

Forward Over-Current

•

Forward Low Current

•

Over-Temperature

•

Input Under-Voltage

•

Input Over-Voltage

•

VC pin Under-Voltage

Picor Corporation • picorpower.com

PI2125

Rev 1.0

Page 7 of 20

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