E-L5973AD Datasheet, PDF (13/22 Pages) STMicroelectronics – 2 A switch step down switching regulator

L5973AD
Additional features and protections
5
Additional features and protections
5.1
Feedback disconnection
In case of feedback disconnection, the duty cycle increases versus the maximum allowed
value, bringing the output voltage close to the input supply. This condition could destroy the
load.
To avoid this dangerous condition, the device is turned off if the feedback pin remains
floating.
5.2
Output overvoltage protection
The overvoltage protection, OVP, is realized by using an internal comparator, which input is
connected to the feedback, that 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 requested for adjusting the output voltage (see test application
circuit), the OVP intervention will be set at:
Equation 1
V_OVP
=
1.3
⋅
R_{-----1----+-----}R_-----2
R₂
⋅
V_FB
Where R₁ is the resistor connected between the output voltage and the feedback pin, while
R₂ is between the feedback pin and ground.
5.3
Zero load
Due to the fact that the internal power is a PDMOS, no boostrap capacitor is required and
so, the device works properly also with no load at the output. In this condition it works in
burst mode, with random repetition rate of the burst.
5.4
Application circuit
In Figure 8 is shown the demo board application circuit, where the input supply voltage,
V_CC, can range from 4 V to 25 V due to the rated voltage of the input capacitor and the
output voltage is adjustable from 1.235 V to V_CC.
Doc ID 9552 Rev 9
13/22