Texas Instruments 3138 155 232931 manual VCO and PLL Self-Calibration, Output Power Programming

CC2420

27 VCO and PLL Self-Calibration

27.1 VCO

The VCO is completely integrated and operates at 4800 – 4966 MHz. The VCO frequency is divided by 2 to generate frequencies in the desired band (2400- 2483.5 MHz).

27.2 PLL self-calibration

The VCO's characteristics will vary with temperature, changes in supply voltages, and the desired operating frequency.

28 Output Power Programming

The RF output power of the device is programmable and is controlled by the TXCTRL.PA_LEVEL register. Table 9 shows the output power for different

In order to ensure reliable operation the VCO’s bias current and tuning range are automatically calibrated every time the RX mode or TX mode is enabled, i.e. in the RX_CALIBRATE, TX_CALIBRATE and TX_ACK_CALIBRATE control states in Figure 25 on page 44.

settings, including the complete programming of the TXCTRL control register. The typical current consumption is also shown.

PA_LEVEL	TXCTRL register	Output Power [dBm]	Current Consumption [mA]
31	0xA0FF	0	17.4
27	0xA0FB	-1	16.5
23	0xA0F7	-3	15.2
19	0xA0F3	-5	13.9
15	0xA0EF	-7	12.5
11	0xA0EB	-10	11.2
7	0xA0E7	-15	9.9
3	0xA0E3	-25	8.5

Table 9. Output power settings and typical current consumption @ 2.45 GHz

29 Voltage Regulator

CC2420 includes a low drop-out voltage regulator. This is used to provide a 1.8 V power supply to the CC2420 power supplies. The voltage regulator should not be used to provide power to other circuits because of limited power sourcing capability and noise considerations.

The voltage regulator input pin VREG_IN is connected to the unregulated 2.1 to 3.6 V power supply. The voltage regulator is enabled / disabled using the active high voltage regulator enable pin VREG_EN. The regulated 1.8 V voltage output is

available on the VREG_OUT pin. A simplified schematic of the voltage regulator is shown in Figure 28.

The voltage regulator requires external components as described in the Application Circuit section on page 19.

When disabling the voltage regulator, note that register and RAM programming will be lost as leakage current reduces the output voltage on the VREG_OUT pin below

1.6V. CC2420 should then be reset before the voltage regulator is disabled.

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