UM1607 datasheet(4/9 Pages) STMICROELECTRONICS

4 / 9 page

Description

UM1607

4/9

DocID024208 Rev 1

For an easy connection of oscilloscope probes to the test points, remove the plastic tip with

the hook from the probes and insert the center pin into the test point terminal. Ground test

points are available in a sufficient amount throughout the board.

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

ST8034HC 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 6 of the ST8034HC

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 VCC_SEL1 and VCC_SEL2 switches

VCC_SEL1 position

VCC_SEL2 position

VCC

GND

x(1)

1. x = don't care, however, please note that a combination of VCC_SEL1 = VCC_SEL2 = GND and

CMDVCC = high puts the ST8034HC device into a deep shutdown mode.

1.8 V

VDD(INTF)

5 V

VDD(INTF)

GND

3 V

MCU

Set by the microcontroller

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