UM1613 datasheet(4/9 Pages) STMICROELECTRONICS

4 / 9 page

Description

UM1613

4/9

DocID024287 Rev 1

2.2

Smartcard interface

The demonstration board contains a full size smartcard connector. Insert the smartcard from

the right-hand side, card contacts facing down. Card presence detection is implemented

(a presence switch inside the card connector, normally open).

2.3

Interface to a microcontroller block

A standard 16-pin header connector with a standard cable is used to interconnect the

ST8034P demonstration board module with a microcontroller block. The voltage level for

communication on this interface is VDD(INTF).

2.4

Default functionality notes



No floating pins: for simple standalone testing, all the input signal levels are softly

defined by pull-up or pull-down resistors on the board, refer to Figure 4: Schematic

diagram.



The PORADJ undervoltage threshold on the VDD(INTF) supply voltage (UVLO) is set by

R1 and R2 to 1.5 V typ. The resistors can be replaced with different values to set

different undervoltage thresholds on VDD(INTF):

VDD(INTF) UVLO threshold (falling) = (R1 + R2) / R2 x VTH(PORADJ)

VDD(INTF) UVLO threshold (rising) = (R1 + R2) / R2 x (VTH(PORADJ)+ VHYST(PORADJ))

For detailed specifications of the voltage threshold values, refer to Table 14 of the

ST8034P datasheet.

The sum of R1 + R2 should be about 100 k

, which is a good compromise between

a sufficient robustness and a minimum current consumption.

Please consider tolerance ranges of the resistors used in the resistor divider and

specifications range of the VTH(PORADJ) to make sure that even in the worst case the

real VDD(INTF) undervoltage deactivation threshold does not fall in the desired operating

voltage range (i.e. consider also voltage supply tolerance range).

Table 1. VCC selection by tristate VCC_SEL switch

VCC_SEL position

VCC

VDD(INTF)

5 V

MCU/floating

1.8 V or controlled by the microcontroller,

if connected.

GND

3.0 V

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