Functional description

STMPS2141, STMPS2151, STMPS2161, STMPS2171

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3

Functional description

3.1

Fault blanking

The STMPS devices feature a 10 ms fault blanking. Fault blanking allows current-limit faults,

including momentary short-circuit faults that occur when hot-swapping a capacitive load,

and also ensures that no fault is issued during power-up. When a load transient causes the

device to enter current limit, an internal counter starts. If the load fault persists beyond the

10 ms fault-blanking timeout, the FAULT output asserts “low”. Load-transient faults less than

10 ms (typ.) do not cause a FAULT output assertion. Only current-limit faults are blanked.

Die over-temperature faults and input voltage drops below the UVLO threshold cause an

immediate fault output.

3.2

Overcurrent/over-temperature protection

In overcurrent or short-circuit condition, the switch limits the current at a value of about

120% of the rated current. If the temperature of the die goes above the limit value, the switch

turns off.

3.3

FAULT conditions

In applications of power switch, 3 types of FAULT conditions are common. These fault

conditions and the response of STMPS21x1 power switches are described in the following

table.

Table 3.

FAULT conditions

Fault

Condition

STMPS21x1 action

Short circuit

Output shorted to GND via resistance

path of < 1

Ω, causing a rapid current

surge

Turn off output until short is removed,

assert FAULT pin

Over-current

Output connected to a load that sinks

current above threshold

Reduces output voltage to reduce the

current. Assert FAULT pin after a blanking

period

Overheating

Temperature of junction exceeds 135°C

due to any reason

Turn OFF output until temperature falls

below 125°C. Asserts FAULT pin

immediately