ST8004 查看數據表（PDF） - STMicroelectronics

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ST8004

Smartcard interface

STMicroelectronics 

Functional description

ST8004

It is recommended to:

1. Keep track C3 as far as possible from other tracks

2. Have straight connection between CGND and C5 (the 2 capacitors on C1 should be

connected to this ground track)

3. Avoid ground loops between CGND,PGND and GND

4. Decoupled VDDP and VDD separately; if the 2 supplies are the same in the application,

then they should be connected in star on the main track.

With all these layout precautions, noise should be at an acceptable level, and jitter on C3

should be less than 100ps.

6.9

6.10

18/26

Deactivation sequence

When a session is completed, the microcontroller sets the CMDVCC line to the HIGH state.

The circuit then executes an automatic deactivation sequence by counting the sequencer

back and ends in the inactive state (see Figure 6.):

● RST goes LOW →(t11 = t10)

● CLK is stopped LOW →(t12 = t11 +½T) where T is approximately 25 µs

● I/O, AUX1 and AUX2 are output into high-impedance state →(t13 = t11 +T)(10 kΩ pull-

up resistor connected to VCC)

● VCC falls to zero →(t14 = t11 +½3T); the deactivation sequence is completed when VCC

reaches its inactive state

● VUP falls to zero →(t15 = t11 +5T) and all card contacts become low-impedance to

GND;

● I/OUC, AUX1UC and AUX2UC remain pulled up to VDD via a 10 kΩ resistor.

Fault detection

The following fault conditions are monitored by the circuit:

Short-circuit or high current on VCC

Removing card during transaction

VDD dropping

Overheating.

There are two different cases (Figure 7.)

1. CMDVCC HIGH: (outside a card session) then, OFF is LOW if the card is not in the

reader, and HIGH if the card is in the reader. A supply voltage drop on VDD is detected

by the supply supervisor, which generates an internal power-on reset pulse, but does

not act upon OFF. The card is not powered-up, so no short-circuit or overheating is

detected.

2. CMDVCC LOW: (within a card session) then, OFF falls LOW if the card is extracted, or if

a short-circuit has occurred on VCC, or if the temperature on the IC has become too

high. As soon as the fault is detected, an emergency deactivation is automatically

performed (see Figure 8.). When the system controller sets CMDVCC back to HIGH, it

may sense OFF again in order to distinguish between a hardware problem or a card

extraction. If a supply voltage drop on VDD is detected while the card is activated, then

an emergency deactivation will be performed and OFF goes LOW.

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