MICRF405 datasheet(18/46 Pages) MICREL

18 / 46 page

Micrel

MICRF405

April 2006

M9999-041906

(408) 955-1690

Main Modes of Operation

Adr

Data

A6..A0

0000000

Mode1=0

Mode0=1

PA2=1

PA1=1

PA0=1

ClkOut_en=1

Sync_en=1

Load_en=1

There are three main modes of operation and these

are controlled by Mode1-0, see Table 9. In “Power

down” mode all blocks are shut down, though the

contents of the registers are preserved. In “Standby”

the crystal oscillator is running and an optional

programmable clock is present on the CLKOUT pin

(Default enabled). This clock can be used as a

micro-controller reference frequency. In “TX“ mode

all blocks are active if not disabled by the user.

Mode1 Mode0

State

Comments

Power down

Keeps Register

configuration

Standby

Crystal Oscillator

running

Transmit mode

Table 9. MICRF405 Main Modes.

Power Amplifier

Adr

Data

A6..A0

0000000

Mode1=0

Mode0=1

PA2=1

PA1=1

PA0=1

ClkOut_en=1

Sync_en=1

Load_en=1

0010111

PA_IB3=1

PA_IB2 =0

PA_IB1=0

PA_IB0=1

PAB_IB3=1

PAB_IB2=0

PAB_IB1=0

PAB_IB0=1

The maximum output power is approximately

10dBm. For maximum output power the load seen

by the PA must be resistive and around 150Ω at

900MHz and 250Ω at 434MHz and 315Hz. The

output power can be programmed with bits PA[2:0]

to eight different levels if bit PA_LDc_en=1 or seven

levels if PA_LDc_en=0, with approximately 3dB

between each step. If PA_LDc_en=0, the PA is

turned of by setting PA[2:0] to 0. For all other

PA[2:0] combinations, the PA is on and has a

maximum power when PA[2:0]=7. If PA_LDc_en=1

the PA is controlled by the lock detector.

A simple

π LC network can be used to provide the

needed impedance and also to reduce the power of

the harmonics to acceptable levels. Such matching

networks for different frequencies are shown on the

Typical Application Circuit.

The bias setting of the PA and the PA buffer is

controlled by bits PA_IB PA[2:0] and PAB_IB

PA[2:0]. The recommended bit setting, shown in

Table 10, is for the different frequency bands.

Typical values of output power and current

consumption for the different power levels for

different frequencies are shown in Table 11. The

settings used are: Modulation[2:0]=2, ClkOut_en=0,

external loop filter.

Frequency band

(MHz)

PA_IB[2:0]

PAB_IB[2:0]

315

434

868

915

Table 10. Recommended Settings of PA_IB and PAB_IB vs. Frequency Band.

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