DS8113-RNG+ datasheet(8/17 Pages) MAXIM

8 / 17 page

Detailed Description

The DS8113 is an analog front-end for communicating

with 1.8V, 3V, and 5V smart cards. It is a dual input-

voltage device, requiring one supply to match that of a

host microcontroller and a separate +5V supply for

generating correct smart card supply voltages. The

DS8113 translates all communication lines to the cor-

rect voltage level and provides power for smart card

operation. It is a low-power device, consuming very lit-

tle current in active-mode operation (during a smart

card communication session), and is suitable for use in

battery-powered devices such as laptops and PDAs,

consuming only 10nA in stop mode. See Figure 1 for a

functional diagram.

Power Supply

The DS8113 is a dual-supply device. 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 sup-

ply 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 internal power-on reset

pulse, tW. A deactivation sequence is executed when

VDD falls below VTH2.

An internal regulator generates the 1.8V, 3V, or 5V card

supply voltage (VCC). The regulator should be supplied

separately by VDDA and PGND. VDDA should be con-

nected to a minimum 5.0V supply in order to provide

the correct supply voltage for 5V smart cards.

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.

The DS8113 card interface remains inactive no matter

the levels on the command lines until duration tW after

VDD has reached a level higher than VTH2 + VHYS2.

When VDD falls below VTH2, the DS8113 executes a

card deactivation sequence if its card interface is

active.

Smart Card Interface

_______________________________________________________________________________________

TEMPERATURE

MONITOR

CARD VOLTAGE

GENERATOR

CLOCK

GENERATION

CONTROL

SEQUENCER

POWER-SUPPLY

SUPERVISOR

I/O TRANSCEIVER

VDD

GND

VDDA

PGND

CP1

CP2

VUP

VCC

XTAL1

XTAL2

CLKDIV1

CLKDIV2

1_8V

5V/3V

CMDVCC

RSTIN

CGND

RST

CLK

I/O

AUX1

AUX2

PRES

OFF

I/OIN

AUX1IN

AUX2IN

DS8113

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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