| | 1 | === Preamplifier Prototype I === |
| | 2 | |
| | 3 | * PCB Layout and Schematic – [http://ohm.bu.edu/~swd/LIDAR/LIDAR_as_built.pcb PCB] • [http://ohm.bu.edu/~swd/LIDAR/LIDAR_1.sch SCH] |
| | 4 | * Photos of prototype: [http://ohm.bu.edu/~swd/LIDAR/photos/lidar1.jpg Photo 1] • [http://ohm.bu.edu/~swd/LIDAR/photos/lidar2.jpg Photo 2] • [http://ohm.bu.edu/~swd/LIDAR/photos/lidar3.jpg Photo 3] • [http://ohm.bu.edu/~swd/LIDAR/photos/lidar4.jpg Photo 4] |
| | 5 | |
| | 6 | Prototype passed a signal, though not without an oscillation at ~350MHz. Pictured is the result of sending a 500mV square wave with a 1ms period and a 10% duty cycle. |
| | 7 | * Oscillation photos: [http://ohm.bu.edu/~swd/LIDAR/photos/LIDAR_trace_1.jpg Photo 1] • [http://ohm.bu.edu/~swd/LIDAR/photos/LIDAR_trace_2.jpg Photo 2] |
| | 8 | |
| | 9 | === Preamplifier Prototype II === |
| | 10 | |
| | 11 | * PCB Layout and Schematic – [http://ohm.bu.edu/~swd/LIDAR/LIDAR_4_layer_2.pcb PCB] • [http://ohm.bu.edu/~swd/LIDAR/LIDAR_2_works.sch SCH] • [http://ohm.bu.edu/~swd/LIDAR/LIDAR_2_works.pdf PDF] |
| | 12 | * BOM – [http://ohm.bu.edu/~swd/LIDAR/LIDAR_BOM.pdf PDF] • [http://ohm.bu.edu/~swd/LIDAR/LIDAR_BOM.csv CSV] |
| | 13 | * PCB Photos: [http://ohm.bu.edu/~swd/LIDAR/photos/LIDAR_v2_front.jpg Front] • [http://ohm.bu.edu/~swd/LIDAR/photos/LIDAR_v2_back.jpg Back] |
| | 14 | |
| | 15 | New PCB layout uses a 4-layer board design, and strictly adheres to board layout suggestions in TI datasheets for both the OPA847 and THS3201. This design does not oscillate. A -200mV DC offset exists when the test pulse cable is connected. If undesirable, can be corrected with a simple offset nulling circuit connected to U1-3 (non-inverting input of OPA847). |
| | 16 | |
| | 17 | Update: 9/26/2011 |
| | 18 | An oscillation has been discovered at 700MHz with a peak to peak voltage of ~120mV. Removal of the .36pF capacitor (C3) in the feedback loop of the OPA847 solves this problem. Smaller oscillations still exist at ~20mV at close to 100MHz, and are currently being addressed. |
| | 19 | |
| | 20 | Update: 9/28/11 |
| | 21 | * Oscillation at ~100MHz with 2nd opamp disconnected (R11 removed) |
| | 22 | [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/100MHz_noR.jpg pic] |
| | 23 | |
| | 24 | * R11 changed to 1k |
| | 25 | * 5pF input [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_5pf_in pic] |
| | 26 | * 10pF input [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_10pf_in pic] |
| | 27 | |
| | 28 | * 100 ohm resistor was placed in series between the output of the photodiode and input of OPA847 (U1-2). |
| | 29 | * 10pF input [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_10pf_in1_100_U1_2_.jpg pic] |
| | 30 | |
| | 31 | * 100pF bypass capacitor added in parallel to both power supplies |
| | 32 | 10pF input [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_10pf_in1_100_U1_2_100pf_byp.jpg pic 1] |
| | 33 | [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_10pf_in1_100_U1_2_100pf_byp1.jpg pic 2] |
| | 34 | [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_1k_10pf_in1_100_U1_2_100pf_byp2.jpg pic 3] |
| | 35 | |
| | 36 | * R11 changed to 4k - severely decreased oscillation, added 30mV offset. |
| | 37 | * 10pF input [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_4k_10pf_in1_100_U1_2_100pf_byp.jpg pic] |
| | 38 | * 10pF input (avg) [http://ohm.bu.edu/~swd/LIDAR/photos/oscillation/R11_4k_10pf_in1_100_U1_2_100pf_byp_avg.jpg pic] |
| | 39 | |
| | 40 | === CompactPCI Power Board === |
| | 41 | The CompactPCI Power Board is a two slot wide 6u cPCI backplane that provides ATX power and RS232 breakouts for a single XCalibur 4301 module. |
| | 42 | Please note that on the version 1 board the ATX 5VSB is connected to ATX 5V. This will prevent the ATX power supply from starting up. Therefore you must not supply the 5VSB to the version 1 board. It is recommended to cut the 5VSB wire ATX pin 9 purple (see http://en.wikipedia.org/wiki/ATX#Power_supply). This problem is resolved in version 1.1. |
| | 43 | |
| | 44 | |
| | 45 | * [http://ohm.bu.edu/~cjlawlor/LIDAR/cPCI_backplane_v1.1.dxf cPCI_backplane_v1.1.dxf] |
| | 46 | * [http://ohm.bu.edu/~cjlawlor/LIDAR/cPCI_backplane_v1.1.zip cPCI_backplane_v1.1.zip] |
| | 47 | * [http://ohm.bu.edu/~cjlawlor/LIDAR/cPCI_backplane_v1.zip cPCI_backplane_v1.zip] |
| | 48 | * [http://ohm.bu.edu/~hazen/LIDAR/cPCI_backplane_v1_sch.pdf cPCI_backplane_v1_sch.pdf] |
| | 49 | * [http://ohm.bu.edu/~hazen/LIDAR/cPCI_backplane_v1_pcb.pdf cPCI_backplane_v1_pcb.pdf] |
| | 50 | * [http://ohm.bu.edu/~cjlawlor/LIDAR/cPCI_backplane_v1_BOM.xlsx cPCI_backplane_v1_BOM.xlsx] |
| | 51 | |
| | 52 | |
| | 53 | The original idea was to design a one-slot backplane-like board which would hold two connectors to mate with the J1 and J2 CompactPCI connectors on the processor board to supply power. |
| | 54 | |
| | 55 | * [http://ohm.bu.edu/~hazen/LIDAR/Mouser_CPCI.pdf Mouser order] |
| | 56 | * [http://ohm.bu.edu/~hazen/my_d0/std/cpci20_rev30.pdf CompactPCI Draft Standard] |
| | 57 | * [http://ohm.bu.edu/~hazen/LIDAR/XCalibur4301-TM-C.pdf XCalibur 4301 manual] |
| | 58 | * [http://ohm.bu.edu/~cjlawlor/LIDAR/XIt4103-DS.pdf XIt4103-DS.pdf] |
| | 59 | |
| | 60 | === Other Documents === |
| | 61 | |
| | 62 | * [http://ohm.bu.edu/~hazen/LIDAR/ADC3295_User_Manual-1_0.pdf ADC3925 User Manual] |
| | 63 | * [http://ohm.bu.edu/~hazen/LIDAR/EVI_ReceiverAmpCircuit.pdf EVI_ReceiverAmpCircuit.pdf] |
| | 64 | * [http://focus.ti.com/lit/an/sboa122/sboa122.pdf SBOA122] |
| | 65 | * [http://www.national.com/onlineseminar/2004/photodiode/PhotodiodeAmplifers.pdf Photodiode Amplifiers] |
| | 66 | * [http://ohm.bu.edu/~hazen/LIDAR/DWEL-1.ods DWEL-1.ods] |
| | 67 | * [http://jp.hamamatsu.com/resources/products/ssd/pdf/g8376_series_kird1051e05.pdf G8376] |
| | 68 | * [http://focus.ti.com/docs/prod/folders/print/opa847.html OPA847] |
| | 69 | * [http://www.ti.com/litv/zip/sboc037a PSPICE model] |
| | 70 | |
| | 71 | === Design Notes === |
| | 72 | |
| | 73 | ADC3925 input is 50 ohms, 0dBm full scale (225mV). 10 bits implies 0.2mV or so LSB. |
| | 74 | |
