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DS8024

Smart Card Interface

14 ______________________________________________________________________________________

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

and

DDA

lines separately. These lines are best posi-

tioned under the connector.

• The DS8024 and the host microcontroller must use

the same V

supply. Pins CLKDIV1, CLKDIV2,

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

CMDVCC, and OFF are referenced to V

; if pin

XTAL1 is to be driven by an external clock, also

reference this pin to V

• 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 (VCC)

should be connected to this ground trace).

• Avoid ground loops among CGND, PGND, and GND.

• Decouple V

DDA

and V

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

and CGND and place near the

DS8024’s V

pin.

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

ferred, ESR < 100mΩ) between V

and CGND

and place near the smart card socket’s C1 con-

tact.

With all these layout precautions, noise should be kept

to an acceptable level and jitter on C3 (CLK) should be

less than 100ps.

Selector Guide

Note: Contact the factory for availability of other variants and

package options.

Denotes a lead-free/RoHS-compliant package.

PART

CURRENT

VOLTAGES

SUPPORTED (V)

SUPPORTS

STOP MODE

PIN-

PACKAGE

DS8024-RJX+ 3.0, 5.0 No 28 TSSOP

DS8024-RRX+ 3.0, 5.0 No 28 SO

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 SO (300 mils) —

21-0042

28 TSSOP —

56-G2020-001

Package Information

For the latest package outline information and land patterns, go

to www.maxim-ic.com/packages

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Smart Card Interface 1

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