STW82102B datasheet(27/67 Pages) STMICROELECTRONICS

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STW82102B

General description

Doc ID 018516 Rev 2

27/67

Figure 12.

Loop filter connection

8.1.9

Voltage controlled oscillators

VCO selection

Within the STW82102B two low-noise VCOs are integrated to cover a wide band from

1500 MHz to 1800 MHz, and from 1900 MHz to 2200 MHz after the division by 2:

●

VCO A frequency range is 3000 MHz to 3600 MHz

●

VCO B frequency range is 3800 MHz to 4400 MHz

VCO frequency calibration

Both VCOs can operate on 32 frequency ranges that are selected by adding or subtracting

capacitors to the resonator. These frequency ranges are intended to cover the wide band of

operation and compensate for process variations on the VCO center frequency.

An automatic range selection is performed when the bit SERCAL rises from ‘0’ to ‘1’ . The

charge pump is inhibited and the pins ICP and VCTRL are set at a fixed calibration voltage

(VCAL). The frequency ranges are then tested to select the nearest one to the desired

output frequency (F

OUT= N*Fref/R) with VCAL input voltage applied. After this selection, the

charge pump is once again enabled and the PLL performs a fine adjustment around VCAL

on the loop filter voltage to lock FOUT, thus enabling a fast settling time.

Two calibration algorithms are selectable by setting the CALTYPE bit.

Setting the CALTYPE bit to ‘1’ guarantees the PLL lock versus temperature variations. Once

programmed at the initial temperature, T0, within the operating temperature range (-40 °C to

+85 °C), the synthesizer is able to maintain the lock status if the temperature drift (in either

direction) is within the limit specified by

ΔTLK, and provided that the final temperature, T

1, is

still inside the nominal range.

Setting the CALTYPE bit to ‘0’ fixes VCAL to the mid point of the charge pump output

(VDD/2). Optimum PLL phase noise performance versus temperature variations with a

reduced

ΔTLK is guaranteed in this case.

The

ΔTLK parameter, specific to each VCO and calibration type, in the STW82102B is

specified in Table 8: Integer-N synthesizer electrical characteristics.

VDD

Buffer

VCTRL

Cal bit

Charge

pump

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