PX 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

• v2.4.3

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:

• https://github.com/pepaslabs/dr-frank-ltz1000
• https://github.com/pepaslabs/hp-03458-66509-clone