U2270B Просмотр технического описания (PDF) - Atmel Corporation

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U2270B

Read/Write Base Station

Atmel Corporation 

Figure 3-4. Battery Operation

7V to 16V

DVS VEXT VS VBatt Standby

Table 3-1. Characteristics of the Various Operation Modes

Operation Mode

One-rail operation

Two-rail operation

Battery-voltage operation

External Components Required

1 voltage regulator

1 capacitor

2 voltage regulators

2 capacitors

1 transistor

2 capacitors

Optional, for load dump protection:

1 resistor

1 capacitor

Supply-voltage Range

5V ±10%

5V ±10%

7V to 8V

6V to 16V

Driver Output

Voltage Swing

≈ 4V

6V to 7V

≈ 4V

Standby Mode

Available

No

No

Yes

3.3 Oscillator (Osc)

The frequency of the on-chip oscillator is controlled by a current fed into the RF input. An inte-

grated compensation circuit ensures a wide temperature range and a supply-voltage–

independent frequency which is selected by a fixed resistor between RF (pin 15) and VS (pin 14).

For 125 kHz, a resistor value of 110 kΩ is defined. For other frequencies, use the following

formula:

Rt[kΩ]=

---1---4----3---7---5----- – 5

f 0 [ kHz ]

This input can be used to adjust the frequency close to the resonance of the antenna. For more

details see Section “Applications” on page 10.

Figure 3-5. Equivalent Circuit of Pin RF

VS

2 kΩ

Rf

RF

6 U2270B

4684E–RFID–02/08

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