MICRF405 datasheet(39/46 Pages) MICREL

39 / 46 page

Micrel

MICRF405

April 2006

M9999-041906

(408) 955-1690

MOD_F

Comments

0..3

Programmable smoothing filter after attenuator. This can be programmed in four steps, and will produce

reasonable results for the highest bit rates.

Table 42. Modulator Filter Setting.

FSKn

Comments

0..5

The bit rate clock is set by dividing the crystal oscillator frequency by FSKClk_K*2^(3+FSKn).

Table 43. Bit Rate Setting.

FSKClk_K

Comments

1..63

The crystal oscillator is divided by this number to produce modulator clock and it is divided further down by

2^(3+FSKn) to produce the bit rate clock.

Table 44. Modulator and Bit Rate Clock Setting.

ASKn

Comments

0..3

The ASK bitrate clock is set by dividing the crystal oscillator frequency by ASKClk_K*2^(5+ASKn)

Table 45. Bit Rate Setting.

ASKClk_K

Comments

1..63

The crystal oscillator is divided by this number and is divided further down by 2^(5+ASKn) to produce the

ASK bitrate clock.

Table 46. Modulator and Bit Rate Clock Setting.

ASK_PN_en

Comments

01010101…pattern is used in the FSK spreader during ASK.

111101011001000 repeated pattern is used in the FSK spreader during ASK.

Table 47. ASK Spreading.

VCO_IB2

VCO_IB1

VCO_IB0

Comments

Bias setting for VCO_Freq=0/1, 860 MHz

Bias setting for VCO_Freq=2/3, 868 MHz

Bias setting for VCO_Freq=4/5, 915 MHz

Bias setting for VCO_Freq=6/7, 950 MHz (**)

(**): When VCO_IB=000b, the bias current is set automatically by the two VCO_freq bit.

Table 48. VCO Bias Bit.

VCO_by

State

Comment

VCO is active

VCO is bypassed

When VCO is bypassed, a differential signal can be applied to the circuit using

pin CPOUT and VARIN

Table 49. VCO Bypass Bit.

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