DS8024-RJX+ datasheet(7/15 Pages) MAXIM

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DS8024

Smart Card Interface

Maxim Integrated

Detailed Description

The DS8024 is an analog front-end for communicating

with 3V and 5V smart cards. Using an integrated

charge pump, the DS8024 can operate from a single

input voltage. The device translates all communication

lines to the correct voltage level and provides power for

smart card operation. It can operate from a wide input

voltage range (3.3V to 6.0V). The DS8024 is compatible

with the NXP TDA8024 and is provided in the same

packages. (Note that the PORADJ pin is not present in

the DS8024. Most applications do not make use of this

input pin, instead using the DS8024’s default reset

threshold.)

Power Supply

The DS8024 can operate from a single supply or a dual

supply. The supply pins for the device are VDD, GND,

VDDA, and PGND. VDD should be in the range of 2.7V

to 6.0V, and is the supply for signals that interface with

the host controller. It should, therefore, be the same

supply as used by the host controller. All smart card

contacts remain inactive during power on or power off.

The internal circuits are kept in the reset state until VDD

reaches VTH2 + VHYS2 and for the duration of the inter-

nal power-on reset pulse, tW. A deactivation sequence

is executed when VDD falls below VTH2.

An internal charge pump and regulator generate the

3V or 5V card supply voltage (VCC). The charge pump

and regulator are supplied by VDDA and PGND. VDDA

should be connected to a minimum 3.3V (maximum

6.0V) supply and should be at a potential that is equal

to or higher than VDD.

The charge pump operates in a 1x (voltage follower) or

2x (voltage doubler) mode depending on the input

VDDA and the selected card voltage (5V or 3V).

• For 5V cards, the DS8024 operates in a 1x mode

for VDDA > 5.8V and in a 2x mode for VDDA < 5.8V.

• For 3V cards, the DS8024 operates in a 1x mode

for VDDA > 4.1V and in a 2x mode for VDDA < 4.0V.

Voltage Supervisor

The voltage supervisor monitors the VDD supply. A

220µs reset pulse (tW) is used internally to keep the

device inactive during power on or power off of the VDD

supply. See Figure 2.

TEMPERATURE

MONITOR

CARD VOLTAGE

GENERATOR

AND

CHARGE PUMP

CLOCK

GENERATION

CONTROL

SEQUENCER

POWER-SUPPLY

SUPERVISOR

I/O TRANSCEIVER

VDD

GND

VDDA

PGND

CP1

CP2

VUP

VCC

XTAL1

XTAL2

CLKDIV1

CLKDIV2

5V/3V

CMDVCC

RSTIN

CGND

RST

CLK

PRES

I/O

AUX1

AUX2

OFF

I/OIN

AUX1IN

AUX2IN

DS8024

Figure 1. Functional Diagram

VDD

ALARM

(INTERNAL SIGNAL)

POWER ON

POWER OFF

VTH2 + VHYS2

VTH2

SUPPLY DROPOUT

Figure 2. Voltage Supervisor Behavior

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