7.5

VBUS analog current measurement and OCP

VBUS OCP threshold is set by external serial resistor on VBUS. The gain for the analog reading is set to 42 V/V.

The OCP threshold is set to 0.042 V across Rs.

The OCP VBUS is biased by VCC_VCONN and works only in normal mode.

Equivalent block diagram in TCPP02-M18 for VBUS analog current measurement and OCP is given here after:

Figure 8. Equivalent block diagram in TCPP02-M18

42 V/V

+

-

RS=external resistance

+

-

OCP

Analog

reading

High side amplifier

1.8 V

DIR

FLT_OCP

IANA

R

S = external resistance

OCP

VBUS

(+)

(-)

Provider path

VBUSc

VBUSc

ISENSE

RS

VCC_VCONN

Table 12. Recommended values

Typical current

VBUS OCP threshold

Rs - Sense resistor (normalized

values)

0.5 A

0.9 A

47 mΩ

1.5 A

1.9 A

22 mΩ

3.0 A

4.2 A

10 mΩ

5.0 A

6.0 A

7 mΩ

The OCP is biased continuously: inrush current magnitude is controlled by the user through an external capacitor.

Please refer to the X-NUCLEO-SRC1M1 user manual for more informations on external capacitor to control the

insrush current magnitude.

If an OCP event occurs:

•

VCONN switches, CC switches and gate drivers are shutting down

•

During up to 40 µs typ., this OCP alarm is held (no recovery is possible)

•

After this delay, CC switches are turned ON but VCONN switches and gate drivers are held OFF

The system can be restarted only with a recovery word send by the MCU via the I2C bus.

•

The FLGn signal stays low while the recovery word has not been sent

The recovery word is described in next paragraph

TCPP02-M18

VBUS analog current measurement and OCP

DS13787 - Rev 4

page 13/27