Smart Card Interface

14

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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

tioned under the connector.

• The DS8024 and the host microcontroller must use

RSTIN, PRES, AUX1IN, I/OIN, AUX2IN, 5V/3V,

XTAL1 is to be driven by an external clock, also

• Trace C3 (CLK) should be placed as far as possi-

ble from the other traces.

• The trace connecting CGND to C5 (GND) should

be connected to this ground trace).

• Avoid ground loops among CGND, PGND, and

GND.

supplies are the same in the application, they

should be connected in a star on the main trace.

• Connect a 100nF capacitor (ESR < 100m

Ω)

• Connect a 100nF or 220nF capacitor (220nF pre-

ferred, ESR < 100m

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

Note: Contact the factory for availability of other variants and

package options.

+

Denotes a lead(Pb)-free/RoHS-compliant package.

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

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

PACKAGE

CODE

OUTLINE NO.

LAND

PATTERN NO.

28 SO (300 mils)

W28+6

21-0042

90-0109

28 TSSOP

U28+1

21-0066

90-0171