STMPS2141, STMPS2151, STMPS2161, STMPS2171

Functional description

Doc ID 13793 Rev 4

9/34

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 power switch applications, 4 types of FAULT conditions are common. These fault

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

following Table 3.

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.

Reduces output voltage to reduce the

current. Asserts FAULT pin after a

blanking period

Over-current

Output connected to a load that sinks

current above threshold.

Reduces output voltage to reduce the

current. Asserts 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.

Undervoltage

Input voltage drops below the UVLO

treshold.

Turn OFF output until input voltage rises

above the UVLO treshold plus hysteresis.

Asserts FAULT pin immediately.