EM351-RTR datasheet(24/240 Pages) ETC2

24 / 240 page

EM351 / EM357

Top-Level Functional Description

Figure 3-1 shows a detailed block diagram of the EM35x.

Figure 3-1. EM35x Block Diagram

The EM35x radio receiver is a low-IF, super-heterodyne receiver. The architecture has been chosen to

optimize co-existence with other devices in the 2.4 GHz band (namely, Wi-Fi and Bluetooth), and to minimize

power consumption. The receiver uses differential signal paths to reduce sensitivity to noise interference.

Following RF amplification, the signal is downconverted by an image-rejecting mixer, filtered, and then

digitized by an ADC.

The digital section of the receiver uses a coherent demodulator to generate symbols for the hardware-based

MAC. The digital receiver also contains the analog radio calibration routines, and controls the gain within the

receiver path.

The radio transmitter uses an efficient architecture in which the data stream directly modulates the VCO

frequency. An integrated PA provides the output power. Digital logic controls Tx path and output power

calibration. If the EM35x is to be used with an external PA, use the TX_ACTIVE or nTX_ACTIVE signal to control

the timing of the external switching logic.

The integrated 4.8 GHz VCO and loop filter minimize off-chip circuitry. Only a 24 MHz crystal with its loading

capacitors is required to establish the PLL local oscillator signal.

The MAC interfaces the on-chip RAM to the Rx and Tx baseband modules. The MAC provides hardware-based

IEEE 802.15.4-2003 packet-level filtering. It supplies an accurate symbol time base that minimizes the

synchronization effort of the Ember software and meets the protocol timing requirements. In addition, it

provides timer and synchronization assistance for the IEEE 802.15.4-2003 CSMA-CA algorithm.

The EM35x integrates hardware support for a packet trace module, which allows robust packet-based debug.

This element is a critical component of InSight Desktop, the Ember software IDE, and provides advanced

network debug capability when used with Ember’s InSight Adapter.

3-1

120-035X-000D

Preliminary

EM351-RTR Datasheet(PDF) 24 Page - List of Unclassifed Manufacturers