IEEE 802.15.4 subsystem
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IEEE 802.15.4 subsystem Git Source Tree
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| Source at commit 624caeb00652f6118dc64698b7dad6fa3e5bdcc2 created 6 years 9 months ago. By Werner Almesberger, atusb/: use VR, POWERED, and LED from kicad-libs | |
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| 1 | Replace balun and filter with integrated balun |
| 2 | |
| 3 | |
| 4 | We consider the balun needs for the AT86RF230 and the TI/Chipcon |
| 5 | CC2520 we may try as a design alternative. |
| 6 | |
| 7 | For the AT86RF230, Atmel recommend baluns with integrated filter, |
| 8 | namely the Wuerth 748421245 and the Johanson 2450FB15L0001, both in the |
| 9 | AR86RF230 data sheet. |
| 10 | |
| 11 | For the CC2520, TI recommend a microstrip-based design for the balun, |
| 12 | both in the CC2420/CC243x/CC2480 application note [1] and the reference |
| 13 | design [2], without fully characterizing neither the transceiver's RF |
| 14 | output nor all the components in the balun. |
| 15 | |
| 16 | Johanson lists the 2450FB15L0001 [3] and even a 2450BM15B0002 [3] for |
| 17 | the TI/Chipcon CC2520, but not even Octoparts is able to find a |
| 18 | distributor for these parts. |
| 19 | |
| 20 | Digging deeper, TI reveal more information about the balun in [5]. |
| 21 | |
| 22 | Finally, TI somewhat hesitatingly acknowledge that the Murata balun |
| 23 | LDB182G4510C-110 can be used for the CC2520 [6], with a 3.9 nH inductor |
| 24 | connecting RF_P and RF_N, the balun coupled to GND not directly but via |
| 25 | 10 nF, and finally an LC low-pass filter with 1.5 nH and 2.2 pF at the |
| 26 | output, for EMI compliance. |
| 27 | |
| 28 | Note that this also means that CC2520 and AT86RF230 both have an |
| 29 | impedance of 100 Ohm. |
| 30 | |
| 31 | A balun without filter similar to the Murata part would be the Johanson |
| 32 | 2450BL15K100. |
| 33 | |
| 34 | Manufacturer Part number Package Digi-Key Price/Qty |
| 35 | --------------- ----------------------- ------- --------------- --------------- |
| 36 | Wuerth 748421245 0805-6 732-2230-1-ND 2.15/25 |
| 37 | 732-2230-2-ND 0.753/4000 |
| 38 | Johanson 2450FB15L0001 0805-6 - - |
| 39 | Johanson 2450BM15B0002 0805-6 - - |
| 40 | Johanson 2450BL15K100 0805-6 712-1045-1-ND 0.488/10 |
| 41 | 712-1045-2-ND 0.225/4000 |
| 42 | Murata LDB182G4510C-110 0603-6 490-5023-1-ND 0.325/10 |
| 43 | 490-5023-2-ND 0.114/4000 |
| 44 | |
| 45 | [1] http://www.ti.com/litv/pdf/swra098d |
| 46 | [2] http://focus.ti.com/docs/toolsw/folders/print/cc2520em_refdes.html |
| 47 | [3] http://www.johansontechnology.com/images/stories/ip/baluns/Balun_Filter_Combo_Matched_2450FB15L0001_v11.pdf |
| 48 | [4] http://www.johansontechnology.com/images/stories/ip/baluns/balun_filter_combo_matched_2450bm15b0002_v2.pdf |
| 49 | [5] http://www.ti.com/litv/pdf/swra236a |
| 50 | [6] http://e2e.ti.com/support/low_power_rf/f/155/t/15910.aspx |
| 51 | |
| 52 | |
| 53 | Conclusion: the Wurth balun appears to be the safest choice for |
| 54 | prototyping the AT86RF230. Due to its high cost, a circuit with a |
| 55 | discrete filter may be considered for larger quantities. |
| 56 | |
| 57 | For the CC2520, it's probably safest to directly try the Muarta balun |
| 58 | with the recommended discrete filtering circuit. |
| 59 | |
