ADC PCB

[dymnz]

• PCB layout
  • Verify inverting summing amp.
  • Change the resistor on the design manual to the value on current plug board
• Test

[dymnz]

1. DC bias before level shifter should be removed, how?

• Inverting summing amplifier

[dymnz]

• 2nd stage amp. should be changed to inverting amp.
• Level shifter should be changed to inverting summing amp. w/ potentiometer.

[dymnz]

• LPF-HPF: #TLV2376IDGKR
  • 2 ch
• Non-inverting: #TLV2376IDGKR
  • Change to Inverting + non-inverting two stage amp
• Level-shifter: #OPA388IDR
  • 1 ch

Update: TLV2376IDGKR is single supply

[dymnz]

BOM:

• http://www.mouser.tw/ProductDetail/Texas-Instruments/TLV2376IDGKR/?qs=S8zVn2bBIh%2f6p0pqUwewzw==

• http://www.mouser.tw/ProductDetail/Texas-Instruments/OPA388IDR/?qs=sGAEpiMZZMtOXy69nW9rMyp6kOSQ7u4m%2FreX0qCEEae8Tjp3FDKvRA%3D%3D

  • 5

[dymnz]

Supply voltage:

• Power supply IC:

  • Check: https://electronics.stackexchange.com/questions/79307/what-are-the-ways-to-make-a-dual-power-supply-from-a-single-voltage-source
  • 0~5V
    • Outer supply
  • +-2.5V
    • LT3090 -1~-36V to 0~-32V, 5V to
      +-2.5V in reference
    • MAX1044

• Additional circuit:

  • LPF-HPF: +-2.5V
  • 2-stage amp: +-2.5V
  • Level-shifter: 0~5V

TLV3542: (2ch * 2 | +-2.5V)

1. LPG-HPF
2. Inverting amp

OPA388IDR: (1ch * 1 | 0~5V)

1. Inverting adder

Misc:

• Pot
  • 3362P dimension
  • 20k ohm pot.
  • 10k ohm pot.
  • 50k ohm pot.
• Res 0603
  • 1k, 10k, 20k, 40k, 50k, 11k, 22k
• Cap 0805
  • 1u, 10n

[dymnz]

MAX1044

• 5.11 +- 7mV
• 2.55 +- 7mV
• -2.4 +- 6mV

OK

[dymnz]

Additional Circuit

• Frequency response not so good. Target: 10~500Hz
• LPF cap should be 20nF, 22nF used
• Max signal Vpp @ 1Hz = 80mV
• Max signal Vpp @ 10Hz = 1.2V <-- low -3db
• Max signal Vpp @ 100Hz = 1.8V
• Max signal Vpp @ 300Hz = 1.2V <-- high -3db
• Max signal Vpp @ 400Hz = 900mV
• Max signal Vpp @ 500Hz = 700mV
• High DC at output with 0-input, 4V lowest
  • --> larger DC res. at inverting summer
  • Refer to DC offset after Inverting amp. #32

Power draw

• +5.0V: 0mA
• +2.5V: 18mA
• • 2.5V: 18mA
• MAX1044 has a linear output voltage drop w.r.t output current, 20mA => 1V drop

TODO

• LPF cap change

• Change -IN cap to 45nF To 15K(x) 22n(o)
• MAX1044 supply test Probably won't work
• New power supply circuit
  • LD1117: 9V supply / o: +5, +2.5, -2.5
  • Tested, working current 9V 30mA for AED+circuit

Improvement

• Add supply port for AED

[dymnz]

Additional Circuit 2

• Frequency response not so good. Target: 10~500Hz
• LPF cap 15k/22nF
• Max signal Vpp @ 10Hz = 2.35V <-- low -3db
• Max signal Vpp @ 100Hz = 4V
• Max signal Vpp @ 200Hz = 3.48V
• Max signal Vpp @ 300Hz = 3 V <-- high -3db
• Max signal Vpp @ 400Hz = 3V
• Max signal Vpp @ 500Hz = 2.2V

Not proper roll-off

[dymnz]

#12 (comment)