Micrel, Inc.

MICRF113

June 2008

13

M9999-060208

(408) 944-0800

.

Application Information

L1

820nH

(470nH)

C1

10 F

6.3V

R7

R2

100k

Y1

13.560MHz

(9.4375MHz)

C2

100pF

50V

C11 NP

C12 NP

(4.7 F/

6.3V/

0805)

C6 NP

C7

4.7pF

(6.8pF)

C5

12pF 50V

(10pF 50V)

C16 NP

L4

68nH

(150nH)

L5

ANTENNA

C10

0.1 F

50V

C14

18pF

C13

18pF

C15 NP

1nF

4

5

6

3

3

2

2

1

1

XTLOUT

MICRF113YM6

XTLIN

ASK

VDD

VSS

PAOUT

Vdd

REFOSC

DATA

Figure 6. ASK 433.92MHz and (315MHz)

Notes:

1.

Components labeled NP are not placed.

2.

Values without parentheses are for 433.92 MHz and values in parentheses are for 315MHz.

3.

Value of R7 is selected to vary the output power.

The MICRF113 is well suited to drive a 50-ohm source,

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)

L1

(nH)

C5

(pF)

L4

(nH)

C7

(pF)

Y1 (MHz)

315.0

470

10

150

6.8

9.84375

433.92

820

12

68

4.7

13.5600

Table 1

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

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.