MIC2025/2075

Micrel

MIC2025/2075

10

March 2000

Short-Circuit Applied to Enabled Output

When a heavy load or short-circuit is applied, a large transient

current may flow until the current-limit circuitry responds.

Once this occurs the device limits current to less than the

short-circuit current limit specification. See the Short-Circuit

Transient Response graph under Functional Characteristics.

Current-Limit Response—Ramped Load

The MIC2025/75 current-limit profile exhibits a small foldback

effect of about 200mA. Once this current-limit threshold is

exceeded the device switches into a constant current mode.

It is important to note that the device will supply current until

the current-limit threshold is exceeded. See the Current-Limit

Response graph under Functional Characteristics.

Fault Flag

The FLG signal is an N-channel open-drain MOSFET output.

FLG is asserted (active-low) when either an overcurrent or

thermal shutdown condition occurs. In the case where an

overcurrent condition occurs, FLG will be asserted only after

the flag response delay time, t

that FLG is asserted only upon valid overcurrent conditions

and that erroneous error reporting is eliminated. For ex-

ample, false overcurrent conditions can occur during hot-plug

events when a highly capacitive load is connected and

causes a high transient inrush current that exceeds the

current-limit threshold. The FLG response delay time t

typically 3ms.

Undervoltage Lockout

Undervoltage lockout (UVLO) prevents the output MOSFET

from turning on until V

voltage detection functions only when the switch is enabled.

Short-Circuit Fault

Thermal Shutdown

Reached

Load Removed

(Output Reset)

Figure 1. MIC2075-2 Timing: Output Reset by Removing Load

Short-Circuit Fault

Thermal Shutdown

Reached

Load/Fault

Removed

Figure 2. MIC2025-2 Timing