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DKMD2081 Datasheet(PDF) 8 Page - RF Micro Devices |
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DKMD2081 Datasheet(HTML) 8 Page - RF Micro Devices |
8 / 18 page 8 of 18 RFMD2081 DS140110 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. less significant. At higher output frequencies the inductance of the bond wires (about 0.5nH on each pin) becomes more sig- nificant. The following diagram is a simple model of the modulator output: It is recommended to use a 4:1 balun on the modulator output, converting from the single ended 50 system to a 200 differential load. The RFMD2081 evaluation board has an RFXF8553 wideband transmission line transformer. Serial Interface All on-chip registers in the RFMD2081 are programmed using a proprietary 3-wire serial bus which supports both write and read operations. Synthesizer programming, device configuration and control are achieved through a mixture of hardware and software controls. Certain functions and operations require the use of hardware controls via the ENBL, MODE, and RESETX pins in addition to programming via the serial bus. Alternatively there is the option to control the chip completely via the serial bus. The serial data interface can be configured for 4-wire bus operation, by setting the '4WIRE' bit in the SDI_CTRL register high. Then pin 26 is used as the data out pin, and pin 32 is the serial data in pin. Hardware Control Three hardware control pins are provided: ENBL, MODE, and RESETX. The ENBL pin has two functions: to enable the analog circuits in the chip and to trigger the VCO auto-selection and coarse tun- ing mechanisms. The VCO auto-selection and coarse tuning are initiated when the ENBL pin is taken high. Every time the fre- quency of the synthesizer is reprogrammed, ENBL has to be asserted high to initiate these mechanisms and then to initiate the PLL locking. Alternatively following the programming of a new frequency the PLL re-lock self clearing bit could be used. If the device is left in the enabled state for long periods, it is recommended that VCO auto-selection and coarse tuning (band selection) is performed for every 30°C change in temperature. The lock detect flag can be used to indicate when to perform the VCO calibration, it shows that the VCO tuning voltage has drifted significantly with changing temperature. The RESETX pin is a hardware reset control that will reset all digital circuits to their startup state when asserted low. The device includes a power-on-reset function, so this pin should not normally be required, in which case it should be connected to the positive supply. The MODE pin controls which PLL programming register bank is active. Serial Data Interface Control The normal mode of operation uses the 3-wire serial data interface to program the device registers, and three extra hardware control lines; MODE, ENBL and RESETX. When the device is under software control, achieved by setting the SIPIN bit in the SDI_CTRL register high, then the hardware can be controlled via the SDI_CTRL register. When this is the case, the three hardware control lines are not required. If the device is under software control, pins 1 and 9 can be configured as general purpose outputs (GPO). RFMD2081 RF Output 0.5nH 0.5nH 1K 1pF 1K |
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