AN3394 datasheet(7/29 Pages) STMICROELECTRONICS

Part #	AN3394

Description	Antenna design and impedance matching guidelines for CR95HF multiprotocol contactless transceiver IC

PDF	29 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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7 / 29 page

AN3394

Description of DEMO-CR95HF-A and criteria for impedance matching

Doc ID 018754 Rev 5

7/29

1.2

Output impedance of the DEMO-CR95HF-A

demonstration board output circuit

To generate the magnetic field, the antenna is excited by the two CR95HF differential

generators (see Figure 2: CR95HF equivalent output impedance).

Each generator has an output impedance of 13.5

Ω.

Zout is the CR95HF differential output impedance between TX1 and TX2. It is a pure

resistor. The resulting output impedance, Rout, can be measured as shown in Figure 3: Chip

simplified equivalent impedance:

out

()

Figure 2.

CR95HF

equivalent output

impedance

Figure 3.

Chip simplified equivalent

impedance

Where

Zout:

Matching impedance. [

Ω]

Rout:

Matching resistor. [

Ω]

Vout:

Supply voltage of the chip. [V]

AN3394 Datasheet(PDF) 7 Page - STMicroelectronics