DS8024_V3 Datasheet, PDF (14/15 Pages) Maxim Integrated Products – Smart Card Interface

Smart Card Interface
Applications Information
Performance can be affected by the layout of the appli-
cation. For example, an additional cross-capacitance of
1pF between card reader contacts C2 (RST) and C3
(CLK) or C2 (RST) and C7 (I/O) can cause contact C2
to be polluted with high-frequency noise from C3 (or
C7). In this case, include a 100pF capacitor between
contacts C2 and CGND.
Application recommendations include the following:
• Ensure there is ample ground area around the
DS8024 and the connector; place the DS8024
very near to the connector; decouple the V_DD and
V_DDA lines separately. These lines are best posi-
tioned under the connector.
• The DS8024 and the host microcontroller must use
the same V_DD supply. Pins CLKDIV1, CLKDIV2,
RSTIN, PRES, AUX1IN, I/OIN, AUX2IN, 5V/3V,
CMDVCC, and OFF are referenced to V_DD; if pin
XTAL1 is to be driven by an external clock, also
reference this pin to V_DD.
• Trace C3 (CLK) should be placed as far as possi-
ble from the other traces.
• The trace connecting CGND to C5 (GND) should
be straight (the two capacitors on C1 (V_CC) should
be connected to this ground trace).
• Avoid ground loops among CGND, PGND, and
GND.
• Decouple V_DDA and V_DD separately; if the two
supplies are the same in the application, they
should be connected in a star on the main trace.
• Connect a 100nF capacitor (ESR < 100mΩ)
between V_CC and CGND and place near the
DS8024’s V_CC pin.
• Connect a 100nF or 220nF capacitor (220nF pre-
ferred, ESR < 100mΩ) between V_CC and CGND
and place near the smart card socket’s C1 contact.
With all these layout precautions, noise should be kept
to an acceptable level and jitter on C3 (CLK) should be
less than 100ps.
Technical Support
For technical support, go to https://support.maxim-
ic.com/micro.
Selector Guide
PART
CURRENT
VOLTAGES
SUPPORTED (V)
SUPPORTS
STOP
MODE?
PIN-
PACKAGE
DS8024-RJX+
3.0, 5.0
No
28 TSSOP
DS8024-RJX/V+
3.0, 5.0
No
28 TSSOP
DS8024-RRX+
3.0, 5.0
No
28 SO
Note: Contact the factory for availability of other variants and
package options.
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
28 SO (300 mils)
28 TSSOP
PACKAGE
CODE
W28+6
U28+1
OUTLINE
LAND
NO. PATTERN NO.
21-0042
90-0109
21-0066
90-0171
14