HTRC11001T 查看數據表（PDF） - Philips Electronics

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HTRC11001T

HITAG reader chip

Philips Electronics 

Philips Semiconductors

HITAG reader chip

Product specification

HTRC11001T

8 FUNCTIONAL DESCRIPTION

8.1 Power supply

The HTRC11001T works with an external 5 V ±10% power

supply at pin VDD. The maximum DC current is

10 mA + 2-π- × Iant(p) = 137 mA.

For optimum performance, the power supply connection

should be bypassed to ground with a 100 nF capacitor

close to the chip.

8.2 Antenna drivers

The drivers deliver a square shaped voltage to the series

resonant antenna circuit (see Fig.4). Due to the full bridge

configuration of the drivers the output voltage Vant(p-p) is

approximately 10 V, corresponding to Vant(p) = 5 V.

The current flowing through the antenna is sine shaped

and the peak and RMS values are approximately:

Iant(p) = 4-π- × V---R--a--na---tn-(--pt--)

Iant(rms)

=

---1---

2

×

I ant(p )

8.3 Diagnosis

In order to detect an antenna short-circuit or open-circuit

the antenna tap voltage is monitored.

An antenna fail condition is reported in the status

bit ANTFAIL (see Table 5) if the antenna tap voltage does

not go more negative than the diagnosis level voltage

(Vdiag = −1.15 V). This condition is checked for every coil

driver cycle.

8.4 Oscillator with programmable divider

The crystal oscillator at pins XTAL1 and XTAL2 works with

either crystal or ceramic resonators. It delivers the input

clock frequency of 4, 8, 12 or 16 MHz. The oscillator

frequency is divided by a programmable divider (selection

bits FSEL1 and FSEL0) to obtain the carrier frequency of

125 kHz (see Table 3).

Alternatively, an external clock signal (CMOS compatible)

may connected to pin XTAL1. For example, this clock

signal can be derived from the microcontroller clock.

8.5 Adaptive sampling time demodulator

The demodulator senses the absorption modulation

applied by a transponder when inserted into the field. The

signal is picked up at the antenna tap point between

La and Ca. It is divided by Rv and the internal resistor Rint

to a level on pin RX below 8 V (peak value) with respect to

pin QGND (see Fig.4). Internally the signal is filtered with

a second-order low-pass filter.

The antenna current and therefore the tap voltage is

modulated by the transponder in amplitude and/or phase.

This signal is fed into a synchronous demodulator

recovering the baseband signal. The amplification and the

bandpass filter edge frequencies of the demodulator can

be adapted to different transponders via settings in the

configuration pages (see Table 3).

The phase between the driver excitation signal and the

antenna tap voltage depends on the antenna tuning. With

optimum tuning, the phase of the antenna tap voltage is

90° off the antenna driver signal. Detuning of the antenna

resonant circuit results in a change of this phase

relationship. The built-in phase measurement unit allows

the measurement of this phase relationship with a

resolution of 6--1--4-- × 360° = 5.625° . This can be used to

compute a sampling time that compensates the detuning

of the reader antenna.

The phase measurement procedure can be carried out:

• Once before the first communication starts, if the

position of the transponder does not change with

respect to the reader antenna

• During the communication (after sending the write

pulses and before receiving the answer of the

transponder), if the tag is moving.

Before the system is switched into WRITE_TAG mode, the

demodulator has to be frozen. This is internally done by

clamping the input of the filter amplifier unit to the level on

pin QGND. Doing so avoids large transients in the

amplifier and digitizer, which could affect settling times.

In addition to the clamping, there exist other means in the

HTRC11001T which allow further reduction of the settling

times. All the parts of the circuitry which are associated

with these functions are controlled by the bits FREEZE0,

FREEZE1 and THRESET (see Table 2).

For more details concerning write timing, demodulator

setting, power-up sequence, etc. please refer to the

application note “AN 98080 Read/Write devices based on

the HITAG Read/Write IC HTRC110”.

2001 Nov 23

6

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