User's Manual

BT900-Sx Hardware Integration Guide
Intelligent BTv4.0 Dual Mode Module
Americas: [phone] Option 2
Europe: [phone]
Hong Kong: [phone]
www.lairdtech.com/bluetooth
30 CONN-HIG-BT900
6 H ARDWARE I NTEGRATION S UGGESTIONS
6.1 Circuit
The BT900-series module is easy to integrate requiring no external components on the customer’s
board apart from those required by customer for development and in customers end
application.
Checklist (for Schematic):
 VCC
External power source within the operating range, rise time and noise/ripple specification of
BT900. Add decoupling capacitors for filtering the external source. Power-on reset circuitry
within BT900 series module incorporates brown-out detector, thus simplifying power supply
design. Upon application of power, the internal power-on reset ensures module starts
correctly.
 Decide if BT900 is to be powered by 3.3V or 1.8V external Power Supply
BT radio chip in the BT900 has two internal regulators, a high voltage (input pin
BT_VREG_IN_HV) and low voltage (input pin BT_VREG_OUT_HV) regulator. ONLY one
regulator can be used to power radio chip.
Method1: If BT900 is required to operate from 3.3V, connect external 3.3V supply to pin31
BT_VREG_IN_HV and MUST leave pin32 BT_VREG_OUT_HV unconnected.
Pin5(VCC) and pin43(BT_VDD_IO) should be connected to pin31 BT_VREG_IN_HV.
Method2: If BT900 is required to operate from 1.8V, connect external 1.8V supply to pin32
BT_VREG_OUT_HV and MUST leave pin31 BT_VREG_IN_HV unconnected.
Pin5(VCC) and pin43(BT_VDD_IO) should be connected to pin32 BT_VREG_OUT_HV.
 Place decoupling capacitor on pin41 BT_VDD_IO. Value 0.1uF or value suitable to filter the
noise present.
 AIN (ADC) and SIO pin IO voltage levels
BT900 SIO voltage levels are at VCC. Ensure input voltage levels into SIO pins are at VCC
also (if VCC source is a battery whose voltage will drop). Ensure ADC pin maximum input
voltage for damage is not violated.
 External supplied Sleep Clock oscillator for BT Radio chip sleep modes (BT900 pin34,
BT_Ext_DS_CLK).
There is current consumption saving of 114uA when using external 32.768kHz.
227uA is when the internal radio chip 32.768kHz is used.
113uA is when external 32.768kHz oscillator is connected to BT900 (radio chip)
pin34(BT_Ext_DS_CLK). PSKey needs to be changed via smartBASIC command.
Refer to DK-BT900-V01 for schematic and recommended part, Siward OSC863100-SCO-B660
(description: OSC,32.768KHz,+/-25ppm,3.2*2.5*1.2mm,SMD,-40~+85dC).
 UART
Is required for loading customer smartBASIC application script during development (or for
subsequent upgrade). Add connector to allow UART to be interfaced to PC (via UART –
RS232 or UART- USB).
 UART_RX and UART_CTS
SIO_0 (alternative function UART_RX) is an input, set with internal pull-up (in FW). The
pull-up prevents the module from going into deep sleep when UART_RX line is idling.
SIO_3 (alternative function UART_CTS) is an input, set with external pull-down. This pull-down
ensures the default state of the UART_CTS will be asserted which means can send data out
of the UART_TX line. In the case when UART_CTS is not connected (which we do not
recommend).