User Manual

Bluegiga Proprietary Version 1.0

Figure 8: Connections to WRAP THOR 2022-1 for Self-Powered Mode

The terminal marked USB_ON can be any free PIO pin. The PIO pin selected must be registered by

setting PSKEY_USB_PIO_VBUS (0x2d1) to the corresponding pin number.

10.5 B

-P

OWERED

ODE

In bus-powered mode the application circuit draws its current from the 5V VBUS supply on the

USB cable.

WRAP THOR 2022-1 negotiates with the PC during the USB enumeration stage about power

consumption.

For Class 2 Bluetooth applications, CSR recommends that the regulator used to derive 3.3V from

VBUS is rated at 100mA average current and should be able to handle peaks of 120mA without

foldback or limiting. In bus-powered mode, WRAP THOR 2022-1 requests 100mA during

enumeration.

For Class 1 Bluetooth applications, the USB power descriptor should be altered to reflect the

amount of power required. This is accomplished by setting the Persistent Store Key

PSKEY_USB_MAX_POWER (0x2c6). This is higher than for a Class 2 application due to the

extra current drawn by the Transmit RF PA.

When selecting a regulator, be aware that VBUS may go as low as 4.4V. The inrush current (when

charging reservoir and supply decoupling capacitors) is limited by the USB specification (see USB

1.1 specification, section 7.2.4.1). Some applications may require soft-start circuitry to limit inrush

current if more than 10pF is present between VBUS and GND.

The 5V VBUS line emerging from a PC is often electrically noisy. As well as regulation down to

3.3V and 1.8V, applications should include careful filtering of the 5V line to attenuate noise that is

above the voltage regulator’s bandwidth. Excessive noise on the 1.8V supply to the analogue supply

pins of WRAP THOR 2022-1 will result in reduced receive sensitivity and a distorted transmit

signal.

10.6 S

USPEND

URRENT

USB devices that run off VBUS must be able to enter a suspended state, whereby they consume less

that 0.5mA from VBUS. The voltage regulator circuit itself should draw only a small quiescent

current (typically less than 100 mA) to ensure adherence to the suspend-current requirement of the

WRAP THOR 2022-1