User's Manual

FLC-BTM501 Datasheet
Flaircomm Microelectronics Confidential
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4.7.2.2 Bus-Powered Mode
In bus-powered mode, the application circuit draws its current from the 5V VBUS supply on the
USB cable. The module negotiates with the PC during the USB enumeration stage about how much
current it is allowed to consume. For Class 2 Bluetooth applications, FLC 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, the module 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 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. Some applications may require soft start circuitry to
limit inrush current if more than 10µF is present between VBUS and GND.
Figure 7: USB Connections for Bus-Powered Mode
4.7.3 I
2
C
PIO8, PIO7 and PIO6 can be used to form a master I2C interface. The interface is formed using
software to drive these lines. It is suited only to relatively slow functions such as driving a LCD,
Keyboard, scanner or EEPROM. In the case, PIO lines need to be pulled up through 2.2Kohm
resistors.