An Example Wireless Sensor Network Transceiver Integrated Circuit (IC)

This appendix describes a short-range, low-power 2.4-GHz Industrial, Scientific, and Medical (ISM) band transceiver designed for the emerging IEEE 802.15.4 wireless standard supporting star and mesh networking (Exhibit 1). When combined with an appropriate microcontroller (MCU), it provides a cost-effective solution for short-range datalinks and networks. Applications include remote control and wire replacement in industrial systems such as wireless sensor networks, factory automation and control, heating and cooling, inventory management, and radio frequency identification (RF ID) tagging. Potential consumer applications include wireless toys, home automation and control, human interface devices, and remote entertainment control.

Exhibit 1: An Example Transceiver

The receiver includes a low-noise amplifier, 1.0-mW PA, VCO, full spread-spectrum encoding and decoding compatible with Institute of Electrical and Electronic Engineers (IEEE) 802.15.4, and buffered transmit and receive data packets for simplified use with low-cost microcontrollers (Exhibit 2). The device supports 250-kbps O-QPSK data in 5.0-MHz channels, per the IEEE 802.15.4 2.4-GHz physical layer specification. A Serial Peripheral Interface (SPI) to the MCU is used for RX and TX data transfer and control (Exhibit 3). This allows MAC, Network, and application software to be supported by an appropriately sized MCU for the use model. In many applications, a large read-only memory (ROM) version of the existing MCU can be used resulting in embedded solutions.

Exhibit 2: Simplified Block Diagram

Exhibit 3: Serial Peripheral Interface

• Features include:

• Power supply range: 2.0 to 3.6 V (Exhibit 4)

  Exhibit 4: Recommended Operating Conditions

  Characteristic	Symbol	Min	Typ	Max	Unit
  Power supply voltage	VDD	2.0	2.7	3.6	Vdc
  Core supply voltage, logic interface	VCORE	—	1.8	—	Vdc
  Digital interface supply	VDDINT	2.0	2.7	3.6	Vdc
  Input frequency	fin	2.405	—	2.480	GHz
  Ambient temperature range	TA	—40	25	85	°C
  Logic input voltage low	Vil	0	—	30 percent VDDINT	V
  Logic input voltage high	Vih	70 percent	—	VDDINT	V
  SPI clock rate	SPICLKi	—	—	8.0	MHz
  RF input power	Pmax	—	−20	0	dBm
  Ref Osc frequency (± 40 ppm over temperature range)	fref	16 MHz only

• 16 channels

• Low power drain

• Power-down modes for power conservation

• RX sensitivity of -90 dBm at 1.0 percent Packet Error Rate (PER)

• Full spread-spectrum encode and decode compatible with 802.15.4

Transition times from power down modes to active modes are short, to allow for maximum power conservation (Exhibit 5).

Exhibit 5: Mode Definitions and Transition Times

Mode	Definition	Transition time
Off	All IC functions Off, Leakage only. Responds to RSTBi	23 ms to Idle
Hibernate	Reference Oscillator Off. IC. Responds to ATTENBi	15 ms to Idle
Doze	Ref Osc On but no CLKO output.	3.3 ms to Idle
Idle	Ref Osc On with CLKO output available. SPI active.
Receive	Ref Osc On, Receiver On, SPI should not be accessed.	144 μs from Idle
Transmit	Ref Osc On, Transmitter On, SPI should not be accessed.	160 μs from Idle
RAM = random access memory.