MICRF113 datasheet(12/21 Pages) MICREL

12 / 21 page

Micrel, Inc.

MICRF113

November 2010

M9999-112310

Application Information

The MICRF113 is well suited to drive a 50Ω load,

monopole or a loop antenna. Figure 6 is an example of a

loop antenna configuration. Figure 6 also shows both

315MHz and 433.92MHz ASK configurations for a loop

antenna. Besides using a different crystal, Table 1 lists

modified values needed for the listed frequencies.

Frequency

(MHz)

(nH)

(pF)

(nH)

(pF)

Y1 (MHz)

315.0

470

150

6.8

9.84375

433.92

820

4.7

13.5600

Table 1. Modified Values for Listed Frequencies

The reference design shown in Figure 6 has an antenna

optimized for using the matching network as described in

Table 1.

Power Amplitude Control Using External Resistor

R7 is used to adjust the RF amplitude output levels

which may be needed to meet compliance regulation. As

an example, the following tables list typical values of

conducted RF output levels and corresponding R7

resistor values for the 50Ω test board, as shown in

Figure 2. R7 of the TX113-1C Demo board using the

loop antenna can be adjusted for the appropriate

radiated field allowed by FCC or ETSI compliance.

Contact Micrel for suggested R7 values to meet FCC

and ETSI compliances.

50Ω Test Board, VDD = 3.0V

R7 (Ω)

Output Power (dBm)

IDD (mA)

12.3

8.5

100

8.0

10.5

500

3.0

7.3

1000

-2.0

5.9

Table 2. Output Power vs. External Resistor @ 315MHz

50Ω Test Board, VDD = 3.0V

R7 (Ω)

Output Power (dBm)

IDD (mA)

9.8

12.5

8.9

100

8.6

11.8

500

2.0

8.9

1000

−3.0

7.3

Table 3. Output Power vs. External Resistor @ 433.92MHz

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