Rainbow Electronics DS8314 - Manual (Page 8)

DS8313/DS8314
Smart Card Interface
8 _______________________________________________________________________________________
Detailed Description
The DS8313 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
DS8313 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. The DS8313 is
designed for applications that do not require communi-
cation using the C4 and C8 card contacts (AUX1 and
AUX2). It is suitable for SIM/SAM interfacing, as well as
for applications where only the I/O line is used to com-
municate with a smart card.
The DS8314 is nearly identical to the DS8313, but only
uses one V
DDA input; therefore, it has reduced capaci-
ty to deliver current to 5V smart cards. However, the
DS8314 can drop into many existing TDA8024 applica-
tions with minimal or no hardware changes. See Figure
1 for a functional diagram.
Power Supply
The DS8313/DS8314 are dual-supply devices. The sup-
ply pins for the devices are V
DD
, GND, and V
DDA
. V
DD
should be in the 2.7V to 6.0V range, 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 V
DD
reaches V
TH2
+ V
HYS2
and for the duration of the internal power-on reset
pulse, t
W . A deactivation sequence is executed when
V DD falls below V TH2 .
An internal regulator generates the 1.8V, 3V, or 5V card
supply voltage (V
CC ). The regulator should be supplied
separately by V DDA . V DDA should be connected to a
minimum 4.75V supply to provide the correct supply
voltage for 5V smart cards.
TEMPERATURE
MONITOR
CARD VOLTAGE
GENERATOR
CLOCK
GENERATION
CONTROL
SEQUENCER
POWER-SUPPLY
SUPERVISOR
I/O TRANSCEIVER
V DD
GND
*USED ONLY ON THE DS8313.
V DDA
V
DDA
*
V CC
XTAL1
XTAL2
CLKDIV1
CLKDIV2
1_8V
RSTIN
CGND
RST
CLK
I/O
PRES
OFF
5V/3V
CMDVCC
I/OIN
DS8313
DS8314
Figure 1. Functional Diagram
V DD
ALARM
(INTERNAL SIGNAL)
POWER ON
t W t W
POWER OFF
V
TH2
+ V
HYS2
V
TH2
SUPPLY DROPOUT
Figure 2. Voltage Supervisor Behavior