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MediaTek Offers Cat-NB2 Modem

July 25, 2017

Author: Linley Gwennap

MediaTek is the latest company to deliver an NB-IoT modem, rolling out the MT2625. It reduces system cost by integrating the RF filters and power-management unit (PMU). The MT2625 still requires an external power amplifier (PA) and antenna switch to complete the RF front end. The MT2625’s RF unit supports all NB-IoT bands defined in Release 13 and Release 14, ranging from 450MHz to 2.1GHz.

The company simplified the new design by implementing only the low-bandwidth NB-IoT standard, also called Cat-NB1/NB2, which operates at just 126kbps on the downlink and 158kbps on the uplink. Unlike most other IoT modems, however, the chip can’t handle Cat-M1, which operates at about 300kbps. This restriction makes the MT2625 well suited to remote devices that transmit only small amounts of data.

The MediaTek chip has a microcontroller subsystem featuring a Cortex-M4 CPU running at 104MHz. It integrates 4MB of PSRAM and 4MB of NOR flash to eliminate external memory. A separate DSP core offloads most of the modem functions from the CPU, freeing it to run simple customer applications using a basic RTOS.

The combination of the MCU, PMU, modem, and RF front end enables highly compact designs. MediaTek demonstrated a tiny 16mm x 18mm module containing a complete NB-IoT modem. The MT2625 is due to enter production later this quarter, just as the major Chinese operators are rolling out their NB-IoT service. The MT2625’s low price and high integration should make it a popular choice for basic IoT devices that need low-speed cellular connectivity, particularly in China.

Subscribers can view the full article in the Microprocessor Report.

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