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ADF7901BRU データシート(PDF) 10 Page - Analog Devices |
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ADF7901BRU データシート(HTML) 10 Page - Analog Devices |
10 / 12 page ADF7901 Preliminary Technical Data Rev. PrD | Page 10 of 12 3pF 8pF 22nH 27nH 5.6pF DVDD RFOUT RSET 3.6k Ω CREG2 2.2mF 220nF CVCO CPOUT VCOIN VCOIN FSK1 FSK2 FSK3 OOK_SEL TxDATA CE 9.8304MHz 33pF 33pF GND OSC2 OSC1 ANTENNA ADF7901 PA_EN RSET_FSK RSET_OOK 3.6k Ω 3.6k Ω CREG1 2.2mF 3pF 1.5pF 22nH 36nH MATCHING 50 V TO ANTENNA 5TH ORDER LOW PASS FILTER MATCHING RFOUT TO 50V NOTES 1. DECOUPLING CAPACITORS HAVE BEEN OMITTED FOR CLARITY. Figure 8. Applications Diagram for the ADF7901 in a Remote Control System LAYOUT GUIDELINES The layout of the board is crucial to ensuring low levels of spurious and harmonics. Decoupling Decoupling capacitors (high frequency 22 pF, low frequency 100 nF) should be placed as close as possible to the supply pins on the part. Low size 0402 and 0603 components are recom- mended for the high frequency rejection on the supply. Regulator Stability A minimum of 1 µF is needed on both CREG1 and CREG2 to ensure stability. An additional 22 pF capacitor can be added to reject higher frequency noise. Since many of the internal block run off the regulator it is critical to reduce the noise on this. Low size 0402 and 0603 components are recommended for the high frequency rejection on the supply. Grounding Emphasis should be placed on the grounding once the decoupling capacitors have been added. The PA stage switches currents of 15 mA in max power mode. This will cause changes in the ground resulting in large return currents which can radiate to other parts of the board. The shortest and least obstructed ground from RFGND back to the ground of the battery should be ensured. A 4-layer board will help, as well as flooding of the top layer. The ground paths should not have any vias, and should be wide tracks. Supply The supply tracks can be routed through vias, as these act as free inductors on the board and make layout easier on a 2-layer board. See the Decoupling section. Tracks should be wide. Digital Lines Any digital lines should contain a large resistor in series. This impedance will block signals of many frequencies including harmonics and the carrier frequency. Long control lines can act as an antenna. It can be useful to add capacitance to ground. There will be some capacitance to ground provided by the lines, and at the input of the digital pins. |
同様の部品番号 - ADF7901BRU |
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同様の説明 - ADF7901BRU |
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