2 layers78.1 × 46.4 mm
2 layers48.9 × 45.7 mm
Pxref24
cellularmitosis/px-ref11An LTZ1000-based 7V reference (circuit by Andreas)
- Size
- 48.9 × 45.7 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 78
- Nets
- 22
- Pads
- 139
- Tracks, vias
- 259, 9
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 3
- Created
- 16 Dec 2017
- Updated
- 30 Aug 2022
Overview
Pxref24 is an open-source printed circuit board by cellularmitosis, from the cellularmitosis/px-ref repository on GitHub, published under the MIT licence. It is a 2-layer board of 48.9 × 45.7 mm with 78 parts on 22 nets, routed with 259 tracks and 9 vias.
It is built around the LT1013DD, LTC2057IMS and LTZ1000ACH. Its parts include 15 capacitors, 14 resistors, 5 connectors, 4 diodes and 3 ICs.
Main components
3
LT1013DD
SOIC-8-15V~15V 0.4V/us 0℃~+70℃ 15nA 1MHz 2 200pA 200uV 350uA 5V 700nV/℃ 97dB Reverse-phase input protection SOIC-8 Precision Op Amps ROHSTexas InstrumentsOperational Amplifier
LTC2057IMS
MSOP10High Voltage, Low Noise, Zero-Drift Operational AmplifierAnalog DevicesUncategorised
LTZ1000ACH
TO-997V Ultra Precision ReferenceAnalog DevicesUncategorised
README
README.mdPX Ref
This is an LTZ1000-based 7V reference.
Specifically, this is my board layout of a circuit published by Andreas (of the EEVBlog forum), which in turn is a modification of the 7V reference circuit from the datasheet.
Latest revision
Revision history:
- v2.4.3
- Shortened the board very slightly, as the fit in a TEKO 371.16 was just a bit tight.
- Added two 0.1" holes near LTZ1000 to allow securing a 3D-printed cap.
- Added more via's in the thermal equalization ring around the LTZ1000.
- v2.4.2
- ???
- v2.4.1
- Used larger pads on the TO-99 footprint (easier to solder).
- Moved the input and (buffered) output caps directly onto the board.
- v2.4
- The board is slightly smaller and fits within a TEKO 371.16 enclosure.
- The chassis-ground jumper has been removed (these can now be linked with a small wire).
- The center pin of the R4/R5 divider has been exposed ("T SET") for off-board manipulation.
- The LTC2057 shutdown pins have been exposed for off-board control.
- v2.3
- The "b" variant has been merged back into a single board design (R4, R5 and R45 are now all on the same board design).
- The LTC2057 shutdown pins are now left floating.
- v2.2, v2.2b
- 2.2 uses a single divider footprint (called R45) for R4 and R5.
- 2.2b uses separate footprints for R4 and R5.
- An output buffer was added (LTC2057).
- Errata:
- A mistake was made with the LTC2057 shutdown pins which will result in self-heating of a few degrees in the LTC2057. The work-around is to disconnect pins 1 and 8 of the LTC2057.
- v2.1
- Added a jumper to optionally link GND to a chassis standoff.
- Used smaller capacitor footprints.
- Exposed the star ground as a solderable terminal.
- Switched D1 from a 1N4001 to a 1N4148.
- Used smaller footprints for D1 and D2.
- Errata:
- Andreas capacitor C15 was accidentally left off of this board design. This cap isn't critical, but a work-around is to bodge a 0.1uF cap across pins 5-6 of the LT1013.
- v2
- Switched to a simpler, 2-layer, 50mm x 50mm board design.
- v1
- First design. 4-layer with via stitching for a mild EMI shielding effect.
- This board was never ordered and tested.
Schematic
Andreas' original schematic: png
My adapted version of Andreas' schematic: pdf
Purchasing
You can order a copy of this board from OSHPark: link
Discussion
My posts to the EEVBlog forum about this design: link link
The naming of this board was inspired by other LTZ1000 references: KX, FX, MX, CX, QX
See also:
Parts
78| Qty | Value | Footprint | References |
|---|---|---|---|
| 28 | Val** | Via_016 | H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H***, H*** +12 |
| 12 | 0.1uF | BOXCAP_01_03_02_059A | C1, C2, C4, C8, C9, C11, C12, C14, C15, C30, C32, C33 |
| 5 | CONN_1X1 | 1pin_040_069 | P1, P2, P3, P4, P5 |
| 5 | Val** | 1pin_032_058 | H***, H***, H***, H***, H*** |
| 4 | 10k | R_AXIAL_0W25_059A_PL | R6, R19, R30, R31 |
| 2 | 10nF | BOXCAP_01_03_02_059A | C13, C31 |
| 2 | 1N4148 | DIODE_SS_059A_PL | D1, D2 |
| 2 | 70k | R_BOX_HERMETIC_PL | R2, R3 |
| 1 | 120 | R_BOX_HERMETIC_PL | R1 |
| 1 | 13k | R_BOX_PL | R4 |
| 1 | 13k/1k | R_BOX_DIVIDER_PL | R45 |
| 1 | 1M | R_AXIAL_0W25_059A_PL | R7 |
| 1 | 1N5819 | DIODE_1A_069A_PL | D4 |
| 1 | 1k | R_AXIAL_0W25_059A_PL | R8 |
| 1 | 1k | R_BOX_PL | R5 |
| 1 | 22R | R_AXIAL_0W25_059A_PL | R32 |
| 1 | 22nF | BOXCAP_01_03_02_059A | C3 |
| 1 | 2N3904 | TO-92_Q_EBC_059Bo_PL | Q1 |
| 1 | 400k | R_AXIAL_0W25_059A_PL | R9 |
| 1 | HOLE | hole_M3 | H1 |
| 1 | LT1013 | DIP8_059A_PL | U2 |
| 1 | LTC2057 | SO-8 | U30 |
| 1 | LTZ1000A | TO-99_PL | U1 |
| 1 | OSHW-logo_silkscreen-front_3mm | OSHW-logo_silkscreen-front_3mm | G*** |
| 1 | Val** | hole_M3 | H*** |
| 1 | ZENER | DIODE_SS_059A_PL | D3 |
Questions
How big is the Pxref24 PCB?
It measures 48.9 × 45.7 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Pxref24 use?
78 parts, built around the LT1013DD, LTC2057IMS and LTZ1000ACH. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Pxref24 KiCad files?
From the cellularmitosis/px-ref repository on GitHub, at the commit this page was made from: the board is kicad/pxref24.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pxref24 design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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