MICRF507 datasheet(29/47 Pages) MICREL

29 / 47 page

Micrel, Inc.

MICRF507

October 2, 2013

Revision 2.2

12pF

39pF

12pF

12nH

ANT (pin 5)

Figure 18. LC Filter

This filter is designed for

the 490MHz band with 50Ω

terminations. Component values may have to be tuned to

compensate for layout parasitics.

Frequency Modulation

The MICRF507 supports two methods of FSK modulation,

selected with the Modulation field as shown in Table 18:

VCO modulation (enabled when Modulation1 is bit set to

0) and divider modulation (Modulation1 bit set to 1). The

Modulation0 bit must always remain 0.

Modulation1 Modulation0

State

Closed loop VCO-modulation

Not in use

Modulation by A,M and N

Not in use

Table 18. Modulation Field

Bits from the microcontroller to be transmitted enter at the

DATAIXO pin. See Table 19.

The modulation index ß must be a minimum of 2.

It is

given by

DEV

in which fDEV is the single-sided deviation and rb is the bit

rate. Another constraint on fDEV is

fDEV

≥ r

b + fOFFSET

where fOFFSET is the total frequency offset between the

receiver and the transmitter:

The calculated fDEV should be used to calculate the needed

receiver

bandwidth,

see

“Switched

Capacitor

Filter”

section.

VCO Modulation

Frequency Divider Modulation

Set Modulation[1:0] to

Means of modulation

VCO modulation using modulator

Divider modulation by switching between

A0/M0/NO and A1/M1/N1

Refclk_K, Mod_clkS, Mod_I, Mod_A,

Mod_F

A0, M0, N0, A1, M1, N1

PLL bandwidth required

Lower than 1/10 of bit rate

Higher than 2x bit rate

Bitstream constraints

DC balance required

None

Instantaneous frequency

waveform (spectrum)

determined by

PLL transient response

Table 19. Modulation Modes

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