Техническая Спецификация для STMicroelectronics Evaluation board for A5970AD EVALA5970AD EVALA5970AD

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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.

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 (

), the 

OVP intervention will be set at:

Where R

 is the resistor connected between the output voltage and the feedback pin, and 

 is between the feedback pin and ground.

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



=