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The duration for which load transients are allowed can be adjusted using an appropriate capacitor value from

ITIMER pin to ground. The transient overcurrent blanking interval can be calculated using Equation 5.

ITIMER

(nF)

(V)

(ms)

( A)

u '

(5)

Leave the ITIMER pin open to allow the part to break the circuit with the minimum possible delay.

Table 8-1. Device ITIMER Functional Mode Summary

ITIMER Pin Connection

Timer Delay before Overcurrent response

OPEN

0 s

Capacitor to ground

As per Equation 5

Short to GND

ITIMER Pin Fault - Part Shuts Off

Note

1. Shorting the ITIMER pin to ground is detected as a fault and the part shuts down. This ensures

robust eFuse behavior even in case of single point failure conditions. Refer to the Fault Response

section for details on the device behavior after a fault.

2. Larger ITIMER capacitors take longer to charge during start-up and may lead to incorrect fault

assertion if the ITIMER voltage is still below the pin short detection threshold after the device has

reached steady state. To avoid this, it is recommended to limit the maximum ITIMER capacitor to the

value suggested by the equation below.

53000

GHI

ITIMER

GHI

D,ON

dvdt

+ 3.6V

= t

+ C

u ¨

Where

• tGHI is the time taken by the device to reach steady state

• tD,ON is the device turn-on delay

• Cdvdt is the dVdt capacitance

• Idvdt is the dVdt charging current

It is possible to avoid incorrect ITIMER pin fault assertion and achieve higher ITIMER intervals if

needed by increasing the dVdt capacitor value accordingly, but at the expense of higher start-up time.

Once the part shuts down due to a Circuit Breaker fault, it can be configured to either stay latched off or restart

automatically. Refer to the Fault Response section for details.

8.3.3.3 Short-Circuit Protection

During an output short-circuit event, the current through the device increases very rapidly. When an output short-

circuit is detected, the internal fast-trip comparator turns off the output within the tSC. The comparator employs a

scalable threshold which is equal to 2.1 × ILIM. This enables the user to adjust the fast-trip threshold as per

system needs rather than using a fixed threshold which may not be suitable for all systems. After a fast trip

event, the device restarts in a current limited mode to try and restore power to the load quickly in case the fast

trip was triggered by a transient event. However, if the fault is persistent, the device will stay in current limit

causing the junction temperature to rise and eventually enter thermal shutdown. See Overtemperature

Protection (OTP) section for details on the device response to overtemperature.

In some of the systems, for example servers or telecom equipment which house multiple hot-pluggable cards

connected to a common supply backplane, there can be transients on the supply due to switching of large

currents through the inductive backplane. This can result in current spikes on adjacent cards which could be

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TPS25980

SLVSFR1 – AUGUST 2020

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