6.8 USB Micro-AB Connector

The SLSTK3701A board is equipped with a USB Micro-AB connector interfacing with the EFM32's USB peripheral. This allows the de-

velopment and evaluation of applications using USB in both host and device mode. For host mode, the board can supply 5V power to

the USB VBUS if the board itself has been powered using the debug-USB connector. The VBUS power switch also provides an over-

current flag which can be read in order to detect if a connected device draws too much current.

The secondary AEM channel (see chapter on Advanced Energy Monitoring) is placed between the USB connector and the EFM32, and

allows monitoring of the current sourced from the USB cable when developing a bus-powered USB application. The AEM circuit in-

cludes an input filter and a sense resistor on the VBUS line, which could potentially influence USB compliance testing. If it is required,

the AEM circuit can be bypassed by removing some components and shorting a footprint on the PCB. More details about this can be

found in the schematic.

The secondary AEM channel will only measure current consumption when the power selector switch is set to the "USB" position.

The EFM32 has an internal LDO regulator that powers the USB PHY inside the chip. 5 V from VBUS is applied to the USB_VREGI pin,

and the output is decoupled on the USB_VREGO pin. When the power select switch is set to the USB position, USB_VREGO is con-

nected to the VMCU net, which powers the chip and all peripherals in the target voltage domain. When the J-Link USB cable is inser-

ted, it is possible to monitor the current that supplies the USB PHY, the EFM32 device and all user peripherals on the board.

VBUS

USB_D+

USB_D-

EFM32

USB_VBUS

USB_VREGI

USB_VREGO

PF10 (USB_DM)

PF11 (USB_DP)

5V

USB_ID

USB_VBUS_ENABLE

USB Micro-AB

Connector

PF5 (USB_VBUSEN)

PF4 (GPIO)

USB_VBUS_OC_FAULT

PF12 (USB_ID)

Power selector switch

SENSE

Advanced

Energy

Monitor

Figure 6.8. USB Connector And Power Supply

UG287: EFM32 Giant Gecko GG11 Starter Kit User's Guide

Peripherals

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