UM0580

Board schematics

17/24

Since the overcurrent protection acts as soon as the voltage on CP+ rises above Vref

(approximately equal to 0.53 V), and given the default value of the shunt resistors (equal to

1.8/4 =0.45

Ω), it follows that the default value for the maximum allowed current (I

equal to:

Equation 1

If necessary, you can decrease the threshold by adding R37 (and similarly R55 and R18)

with the formula:

Equation 2

Similarly, you can increase the threshold by adding R44 (and similar) with the formula:

Equation 3

8.3

Current sensing amplifying network

Figure 11 shows the current sensing amplifying network during phase 2.

A

15

.

1

R

V

I

shunt

Ref

CP

≅

=

R40

R37

with

R40

R37

R40

3.3

V

R37

R37

R40

R

1

I

ref

shunt

CP

>>

⎥⎦

⎤

⎢⎣

⎡

+

−

+

⋅

=

R40

R37

with

R44

R40

1

R

V

I

shunt

ref

CP

>>

⎟

⎠

⎞

⎜

⎝

⎛ +

⋅

=

Figure 11.

Current sensing amplifying network

AM01267v1