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ADF7901BRU-REEL bảng dữ liệu(PDF) 10 Page - Analog Devices |
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ADF7901BRU-REEL bảng dữ liệu(HTML) 10 Page - Analog Devices |
10 / 12 page ADF7901 Rev. A | Page 10 of 12 3pF 8pF 22nH 27nH 5.6pF DVDD RFOUT RSET 3.6k Ω CREG2 2.2 μF 22nF 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 2.2 μF 3pF 1.5pF 22nH 36nH MATCHING 50 Ω TO ANTENNA 5TH-ORDER, LOW-PASS FILTER MATCHING RFOUT TO 50Ω 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. Because many of the internal blocks run off the regulator, it is critical to reduce its noise. Low size 0402 and 0603 components are recommended for the high frequency rejection on the supply. Grounding Emphasis should be placed on grounding once the decoupling capacitors have been added. The PA stage switches currents of 15 mA in maximum power mode. This causes changes in the ground resulting in large return currents that 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 helps, as well as flooding 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, because they act as free inductors and make layout easier on a 2-layer board (see the Decoupling section). Tracks should be wide. Digital Lines Digital lines should contain a large resistor in series. This impedance blocks signals of many frequencies, including harmonics and the carrier frequency. Long control lines can act as antennae. It can be useful to add capacitance to ground. There is some capacitance to ground provided by the lines and at the input of the digital pins. |
Số phần tương tự - ADF7901BRU-REEL |
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Mô tả tương tự - ADF7901BRU-REEL |
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