MICRF507 datasheet(28/47 Pages) MICREL

28 / 47 page

Micrel, Inc.

MICRF507

October 2, 2013

Revision 2.2

Transmitter

Power Amplifier

The maximum output power of the power amplifier (PA) is

approximately 10dBm with a 50Ω load. For maximum

output power, the load seen by the PA must be resistive.

Higher output power can be obtained by decreasing the

load impedance, but this will conflict with impedance

matching to the LNA.

The output power is programmable in seven levels by

means of the PA[2:0] field, with approximately 2.5dB

between steps; see Table 17. The power amplifier is

turned off when PA[2:0] = 000. Otherwise the PA is on and

output power increases with the value of the PA[2:0] field

and is maximum when PA[2:0] = 111.

Setting PA_by=1 causes the PA to be bypassed and

output power to drop by ~22dB. It is still possible to control

the power with PA[2:0] bits.

The LC filter shown in Figure 18 reduces harmonic

emission when placed between the ANT pin and antenna.

Field Name

Number

of bits

Location

of bits

Description

Reference

Modulation

Reg1[7:6]

Modulation selection

Table 18

Mod_I

Reg4[4:0]

Modulator current setting

Mod_A

Reg5[3:0]

Modulator attenuator setting

Mod_F

Reg4[7:5]

Modulator filter setting

Reg0[6:4]

Power amplifier level

Table 17

PA_by

Reg2[4]

Bypass of PA stage on/off

Table 17

Table 16. Register Bit Fields for Transmitter and VCO Modulation

PA2

PA1

PA0

State (approximate attenuation)

PA off

15dB attenuation

12.5dB attenuation

10dB attenuation

7.5dB attenuation

5dB attenuation

2.5dB attenuation

Max output

PA_By

Power Amplifier Enabled

Power Amplifier bypassed, approx 20dB reduced output power.

Table 17. Register Bit Fields for Power Amplifier

MICRF507 Datasheet(PDF) 28 Page - Micrel Semiconductor

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