SEA05

Application information

Doc ID 17014 Rev 1

5/10

5

Application information

Figure 4.

Application information

Note:

A 15

exceed the AMR of Ictrl pin.

As example a potential dangerous phenomenon could happen during converter output

short-circuit.

Consider the steady state operation of the circuit during voltage mode regulation (i.e. the

short (i.e. with negligible impedance) is applied at the output, instantly the positive pin of the

electrolytic capacitor is connected to the SEA05 ground. Since the capacitor acts like a

down to –Vo. This could damage the IC in case the Ictrl pin AMR is violated.

In reality the short is not so severe because it has a some impedance, the electrolytic

capacitor has an ESR and it starts discharging as soon as the short is applied. The Ictrl pin

is brought to a negative voltage anyway. The pin internal structure has been design to be

robust against negative voltage but, since the severity of this phenomenon is proportional to

the output voltage, for some applications an external resistor in series with Ictrl pin helps

protect the IC.

The resistor added in series with Ictrl pin introduces an error in the current sense threshold

voltage.

This error can be calculated considering the Ictrl pin current: this current multiplied by the

value of the external resistor gives the current sense threshold variation.

As example if we add a 15

Ω resistor in series to Ictrl pin, we have

6 µA x 15

Ω = 80 µV, the error is 80 µV / 50 mV = 0.16%