LF Reader IC - TMS3705


LF Reader IC


The transponder base station IC is used to drive the antenna of a TI-RFid transponder system, to send data modulated on the antenna signal, and to detect and demodulate the response of the transponder. The response of the transponder is a FSK signal (frequency shift keyed). The high or low bits are coded in two different high-frequency signals (134.2 kHz for low bits and 123 kHz for high bits, nominal). The transponder induces these signals in the antenna coil according an internally stored code. The energy the transponder needs to send out the data is stored in a charge capacitor in the transponder. The antenna field charges this capacitor in a preceding charge phase. The IC has an interface to an external microcontroller.

There are two configurations for the clock supply to both the microcontroller and the base station IC:

  1. Microcontroller and base station IC are supplied with a clock signal derived from only one resonator: The resonator is attached to the microcontroller. The base station IC is supplied with a clock signal driven by the digital clock output of the microcontroller. The clock frequency is either 4 MHz or 2 MHz depending on the selected microcontroller type.
  2. Both the microcontroller and the base station have their own resonator.

The base station IC has a PLL on-chip that generates a clock frequency of 16 MHz for internal clock supply only. The TMS3705BDRG4 is optimized for higher communication data rates and therefore works without frequency measurement during the write phase.


  • Base Station IC for TI-RFid RF Identification Systems
  • Drives Antenna
  • Sends Modulated Data to Antenna
  • Detects and Demodulates Transponder Response (FSK)
  • Short-Circuit Protection
  • Diagnosis
  • Sleep-Mode Supply Current: 0.2 mA
  • Designed for Automotive Requirements
  • 16-Pin SOIC (D) Package

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Communication Interface
Operating Temperature Range (°C)
Flash (KB)
Dimensions (mm)
Required antenna inductance (µH)
Supply voltage (Vdc)
Transmission Principle
Current Supply (mA)
Device Type
Data Rate (Max) (kbps)
Supply Voltage
I/O (Count)
I/O Logic    
ISO 11785    
-40 to +85    
10 x 6    
100 to 1000    
4.5 to 5.5    
HDX - FSK    
8 Typ    
134.2 kHz    
4.5 to 5.5V    
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