Datasheet

Additional features and protection B5973D
16/44 DocID14117 Rev 4
6 Additional features and protection
6.1 Feedback disconnection
If the feedback is disconnected, the duty cycle increases towards the maximum allowed
value, bringing the output voltage close to the input supply. This condition could destroy the
load.
To avoid this hazardous condition, the device is turned OFF if the feedback pin is left
floating.
6.2 Output overvoltage protection
Overvoltage protection, or OVP, is achieved by using an internal comparator connected to
the feedback, which turns OFF the power stage when the OVP threshold is reached. This
threshold is typically 30% higher than the feedback voltage.
When a voltage divider is required to adjust the output voltage (Figure 15: Short-circuit
current V
IN
= 12 V on page 30), the OVP intervention will be set at:
Equation 1
Where R
1
is the resistor connected between the output voltage and the feedback pin, and
R
2
is between the feedback pin and ground.
6.3 Zero load
Due to the fact that the internal power is a PDMOS, no boostrap capacitor is required and so
the device works properly even with no load at the output. In this case it works in burst
mode, with a random burst repetition rate.
V
OVP
1.3
R
1
R
2
+
R
2
-------------------- V
FB
=