Datasheet

SHORT-CIRCUIT
I
clf
I
clr
V
SS
V
FB
V
OUT
V
SW
I
L
CURRENT LIMIT
SHORT-CIRCUIT
REMOVED
100 mV
LM21212-2
www.ti.com SNVS715A –MARCH 2011–REVISED MARCH 2013
Figure 23. Current Limit Conditions
THERMAL PROTECTION
Internal thermal shutdown circuitry is provided to protect the integrated circuit in the event that the maximum
junction temperature is exceeded. When activated, typically at 165°C, the LM21212-2 tri-states the power FETs
and resets soft start. After the junction cools to approximately 155°C, the device starts up using the normal start
up routine. This feature is provided to prevent catastrophic failures from accidental device overheating. Note that
thermal limit will not stop the die from operating above the specified operating maximum temperature,125°C. The
die should be kept under 125°C to ensure correct operation.
POWERGOOD FLAG
The PGOOD pin provides the user with a way to monitor the status of the LM21212-2. In order to use the
PGOOD pin, the application must provide a pull-up resistor to a desired DC voltage (i.e. Vin). PGOOD will
respond to a fault condition by pulling the PGOOD pin low with the open-drain output. PGOOD will pull low on
the following conditions – 1) V
FB
moves above or below the V
OVP
or V
UVP
, respectively 2) The enable pin is
brought below the enable threshold 3) The device enters a pre-biased output condition (V
FB
>V
SS
).
Figure 24 shows the conditions that will cause PGOOD to fall.
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