MCB1800: USB Host Overcurrent detection does not work

Information in this knowledgebase article applies to:

• MDK
• MCB1800 and MCB4300 board

SYMPTOM

USB Host overcurrent detection does not work on the MCB1800 and MCB4300.

CAUSE

The power switch LM3526M (IC5) provides overcurrent output signals on pin 2 and 3, one for each USB interface. However, the LPC1857 or LPC4357 microcontroller would expect the inverted signal on pin P6_6 and P9_6.

RESOLUTION

The port pins P6_6 AND P9_6 could be used as IO-pins to detect an overcurrent condition. Most likely, these pins would have to be set up as external interrupt inputs. Because of this issue, the Keil MDK USB host middleware does not handle overcurrent detection in our MCB1800 and MCB4300 examples.

MORE INFORMATION

• Refer to Schematics in the MCB1800/4300 User's Guide.
• Refer to USB Interface in the MCB1800/4300 User's Guide.
• Refer to Connecting a USB power switch to the LPC18xx / LPC43xx.

Last Reviewed: Friday, January 8, 2021