LA7209V

No.A0641-11/14

Degree of Modulation Sample Data

Input level

[mVp-p]

Output level

[Vp-p]

Data : high/low

Ra

[

Ω]

Rb

[

Ω]

Rd

[k

Ω]

Antenna current

[mA]

Data : high/low

IC current

[mA]

Data : high/low

Degree of modulatio

[%]

220

4.8/3.9

10

33

1

8.0/6.0

20.7/19.2

10

220

4.8/0.0

10

33

1

8.0/0.1

20.7/19.2

100

* : This IC can support out-of-standard modulation levels by settings using the resistors Ra and Rb described above.

(3) Output level setting

The output level is set by setting the two items (the input level and the idling current) described above and the

damping resistor (Rd) between pins 22 and 23. Note that although an output amplitude (at pins 22 and 23) of about

two times the VCC voltage can be acquired, if the output voltage limit is exceeded, a collision with the pin 5 voltage

occurs and abnormal oscillation due to VCE saturation may occur. In such cases, changes to the antenna structure

(VCC midpoint supply) and/or damping of the output level will be required.

Output Damping Characteristics Sample Data

Rd

[

Ω]

Output level

[Vp-p]

Data : high/low

Ra

[

Ω]

Rb

[

Ω]

Input level

[mVp-p]

Antenna current

[mA]

Data : high/low

IC current

[mA]

Data : high/low

3.9

8.5/4.6

15

4.7

180

7.8/3.7

20.5/19.0

2.2

6.9/3.5

15

4.7

180

7.8/3.7

20.5/19.0

1

4.6/2.5

15

4.7

180

7.8/3.7

20.5/19.0

3.9

8.1/4.3

22

6.8

180

7.0/3.1

20.5/19.0

2.2

6.5/3.3

22

6.8

180

7.0/3.1

20.5/19.0

1

4.1/2.3

22

6.8

180

7.0/3.1

20.5/19.0

3.9

7.5/3.5

33

10

180

6.0/2.5

20.5/19.0

2.2

5.8/2.9

33

10

180

6.0/2.5

20.5/19.0

1

3.5/1.9

33

10

180

6.0/2.5

20.5/19.0

2. Read amplifier (diode detector, bandpass filter, variable amplifier + fixed amplifier) : Data modulation from

the RF signal

(1) Level setting

The input level is determined by voltage division by the capacitors connected between pins 21 and 22 and between

pins 23 and 24 and the IC internal capacitance. However, note that the input dynamic range of pins 21 and 24 is the

same as the VCC voltage.

(2) Variable amplifier gain setting

The gain is determined by the value of the resistor (Rg) connected between pin 19 and ground.

Note that the range of values that may be used for Rg is from 4.7k

Ω (minimum gain) to 100kΩ (maximum gain).

Bandpass Filter Characteristics

– 30

– 20

– 10

– 15

– 25

0

– 5

10

100

1000

10000

Frequency [kHz]

Variable Amplifier Gain Characteristics

0

10

20

15

5

30

25

0

1020

30

40

50

6070

80

90

100

Pin 19 resistance (=Rg) [k

Ω]