BT 900 User Manual download pdf (Page 8)

BT900 Development Kit

Version 1.0

Embedded Wireless Solutions Support Center:

http://ews-support.lairdtech.com

www.lairdtech.com/wireless

Laird Technologies

Americas: +1-800-492-2320

Europe: +44-1628-858-940

Hong Kong: +852-2268-6567 x026

4 FUNCTIONAL BLOCKS

The development board is formed from the following major functional blocks:

4.1 Power Supply

Figure 3: BT900 devboard power supply

The development board can be powered from 4.5-5.5 V supply (into DC jack connector CN1), 3 AAA batteries

(holder J7 mounted on underside of board), or from the USB (type mini-B connector or CON4). The power source fed

into DC jack (CN1) or 3 AAA batteries (J7) is combined together through diodes (diode-OR) and fed to the SW4

switch that allows selection of power source between either USB or the DC jack/AAA.

The 5V from the USB or the DC jack/AAA batteries is regulated down to 3.3V with an on-board regulator on the

development board.

The CON17 default is to select regulated 3.3V.

Note: The development board has a 1.8V regulator for the possibility of powering the BT900 module from a

1.8V rail (by changing the CON17 position). BT900 1.8V operation is not supported in the current

firmware (v9.1.2.0).

The development board’s 3.3V regulator provides power to the BLE module and USB UART bridge interface as well as

to sensors on the development board.

Switch Positions

Development Board Power Source

SW4

CON17 select BT900 Power source

USB (CON4)

Position USB

Position 3.3V always

(for 3.3V operation)

DC jack (CN1) or AAA battery (J7).

Note 1

Position DC

Position 3.3V always

(for 3.3V operation)

Note 1: The development board is powered from DC jack (or AAA batteries) when an external UART source is

to be interfaced to BT900 module (using breakout connector JP5).

On the development board, the power domain:

 VCC_BT supplies the BT900 series module only. Current measuring block on development board only

measures the current into power domain VCC_BT and VREG_IN_HV, VDD_PADS (when the BT900 is powered

by 3.3V (CON17 in the 3.3V position).

 VREG_IN_HV, VDD_PADS supplies the BT900 module (BT radio chip section) only.

 VCC_IO_UART supplies the FTDI chip IO and all other sensors and circuitry.

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BT 900 User Manual Page 8

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