TMS37122 datasheet(28/73 Pages) TI

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Analog Front End IC TMS37122 - Reference Guide

August ’01

2.8.1

Off Mode

The Control Unit is reset with low level at input WDEEN (see Figure 14).

No internal power-on-reset circuit is provided. The circuit is in Off Mode and consumes only

the quiescent current (Iquiet). All battery powered analog parts and current sources are

switched off.

A charge-up of the Charge Capacitor CL is still possible, because the constant current source

required for Voltage Regulator is supplied by VCL. Because of this behavior the battery can

be charged in Battery Charge Mode even if WDEEN is off.

Figure 14: Initialization State Diagram of TMS37122

2.8.2

Standby Mode

The Control Unit includes a Configuration Memory (EEPROM), which can be programmed

via the Test/Trimming Interface. The Configuration Memory determines different modes and

timings. The configuration Memory is read when WDEEN (or WDEENIx) is set to high lev-

el. After the readout the circuit is in the Standby Mode and consumes the Standby Current

(Istby). In this state the unit remains as long as the RF amplitudes of all activated resonant

circuits are below the threshold level VWAKEA.

2.8.3

Init Mode

If a carrier is present and the amplitude at one of the three antennas exceeds the WAKE Sen-

sitivity Level A (WAKESensA1/2/3) for about 1 ms, the EOBI detector is activated.

As soon as the RF Amplitude of one resonant circuit increases, the AGC Amplifier starts to

regulate. After the run-in time (tPdly) the amplitude is checked. If the amplitude exceeds the

threshold level VWAKEA, and the regenerated clock (CLKI) is stable for twait and has no

significant interruptions (>2 clocks), the internal wake signal (WAKEI1, WAKEI2 or

WAKEI3) of the related channel is set (see Figure 15). Until this occurs the current increases

(Iinit) due to clock activity of three channels.

2.8.4

Active Mode

After detection of the first WAKEI the Control Unit disables the other activated Wake Detec-

tors in order to minimize the power consumption.CLKI and EOBI are selected accordingly.

OFF MODE

(Iquiet)

STANDBY

VWAKEA=ON

(Istby)

VRF <

VWAKEA

WDEEN=LOW

WDEEN

= LOW

WDEEN=HIGH

and

TX = LOW

3DSTAT2.CH4

TMS37122 Datasheet(PDF) 28 Page - Texas Instruments

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