SLIM-ADCMUX
8 Channel Analog to Digital Converter

Original Release 5-30-2016.  Revision 0
Update 11-12-2016.  Add explanation for installing AD7685 and LT1864
Update 2-04-2017.  Add connections to the MSA SLIM Control Board
Update 2-06-2017.  Add *Note for C6. (C6 missing from PWB)

SLIM-ADCMUX, 8 Channel Analog to Digital Converter, size-A
Use your mouse's "right click" and "Save Link" to download:
a.  SKSLIM-ADCMUX.sch Rev 0, Schematic, in ExpressPCB software.
b.  PLSLIM-ADCMUX Rev 0, Parts List. Maintained on this page only.
c.  PWB-ADCMUX.pcb Rev 0 , Base artwork for PWB, in ExpressPCB software.  Use this drawing to order the pwb from Express.

    The SLIM-ADCMUX is a selectable, 8 channel, analog to digital converter (ADC). The circuit is divided into two sections, an 8 channel analog switch and a serial analog to digital converter. The SLIM-ADCMUX can be used as an independent 8 channel analog switch by not populating the ADC circuit. Likewise, it can be used as a single channel ADC by not populating the analog switch circuit.

slim/bdslim_adcmux.gif

    The multiplexer is bi-directional, meaning, a signal on the multiplexer input will be transferred to the COM connection or a signal on the COM will be transferred to the multiplexer's input. The multiplexer IC will pass analog or digital signals with a bandwidth limitation greater than 20 MHz.
Specifications:
Size: L = 1.2 in, W =  1.2 in, H = 0.5 in.
Supply voltage: +7.0 v. to +15 v. using internal +5v regulator. (Option, +5v input with no internal regulator.)
Supply Current: less than 5 ma.
Signal input resistance: greater than 1 Meg ohm
Signal input impedance of ADC: Series resistance and capacitance, 3K ohm and 30 pfd.
Input Signal voltage range: 0v to +5.0v.
Control inputs: 5v CMOS
Serial Output Options:
    a. Open Drain.  R6 and R7 are not installed.
    b. 5v CMOS. R6 installed. R7 is not installed.
    c. 3.3v CMOS. (depends on R6/R7). Both R6 and R7 are installed.
Acquisition speed: 150 K samples per second, maximum. (The MSA requires about 1 KSPS)
Resolution Error: +/- 3 bits =  +/- 0.23 mv. max. (in the MSA this equates to plus or minus 0.01 dB or 0.008 degrees)
Note: It is not necessary to shield this module. Whatever noise is coupled into the circuit, the capacitor C6 will shunt it to ground.

    The suggested ADC is either the 16 bit LTC1864, an 8 pin package or the 16 bit AD7685, a 10 pin package. However, other ADC's can be used if the IC package will fit and the command protocall conforms to the pin/pad layout.

Schematic, SKSLIM-ADCMUX
slim/skslim_adcmux.gif

Layout for SLIM-ADCMUX
slim/layslim_adcmuxtop.gif  slim/layslim_adcmuxbot.gif

The following pictures show how to position the LT1864 and AD7685 on the available pads at U3.
slim/expressfiles/LT1864Position.gif  slim/expressfiles/AD7685Position.gif
                       LT1864                                                            AD7685
When installing the LT1864, position its pin 1 on the pwb pad 2. The chip's pin 8 is positioned on the pwb pad 9.
The AD7685 requires some of its leads to be bent for correct alignment. Solder pins 3 and 8 of the chip to the center of the pwb pads 3 and 8. Slightly bend the pins 4, 5, 6, and 7 of the chip downward to align with the pwb pads and solder. Slightly bend the pins 1, 2, 9, and 10 of the chip to align with the pwb pads and solder.

Parts List, PLSLIM-ADCMUX
Revision 0,  5-30-2016
Des.     Value            Part Number                                Digikey Number      Cost             Notes
C1        optional                                                                                                              The optional capacitors can be
C2        optional                                                                                                              any value that user deems
C3        optional                                                                                                              necessary for operation.
C4        optional
C5        optional
C6        .001 uF         C0805C102J5GACTU                     399-1136-1-ND        0.08    * see Note for C6
C7           .1 uF          C0805C104K3RACTU                    399-1168-1-ND        0.08
C8         1.0 uF          C2012X7R1E105K125AB                445-1354-1-ND        0.14
C9          optional
C10        optional
C11        optional
C12        optional
C13        optional
C14        optional
C15        optional
C16        .01 uF         C0805C103K5RACTU                    399-1158-1-ND         0.08   * see Power Option
C17        .1 uF           C0805C104K3RACTU                    399-1168-1-ND         0.08   * see Power Option
C18        10uf/16v    AVX, TPSB106K016R0500             478-5230-1-ND          0.65   * see Power Option
C19        .1 uF           C0805C104K3RACTU                    399-1168-1-ND         0.08
C20        10uf/16v    AVX, TPSB106K016R0500             478-5230-1-ND          0.65
P1        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P2        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P3        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P4        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P5        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P6        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P7        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P8        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P9        Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P10      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P11      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P12      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P13      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P14      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P15      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P16      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
P17      Conn, 2 pin    sold as row of 36 pins                     S1012E-36-ND          0.06
R1        470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R2        470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R3        470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R4        470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R5        470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R6           2.2K            MCR10ERTF2201                RHM2.20KCHCT-ND       0.04  * Optional Pull-up for CMOS or TTL output
R7          4.02K           MCR10ERTF4021                RHM4.02KCHCT-ND       0.04  * Optional Pull-down for 3.3v output
R8           100K           MCR10ERTF1003                RHM100KCHCT-ND        0.04
R12       470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R13       470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R14       470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R15       470 ohm          MCR10ERTF4700               RHM470CHCT-ND           0.04
R16      10  ohm           MCR10ERTF10R0              RHM10.0CHCT-ND           0.04  * see Power Option
Q1        2N7002  FET      2N7002-7-F                     2N7002-FDICT-ND            0.15 
U1        78L05            78L05ACU                                497-1183-1-ND             0.77  * see Power Option
U2       74LV4051     SN74LV4051ADR                     296-3827-1-ND                0.45
U3        AD7685        AD7685BRMZ                         AD7685BRMZ-ND         16.16
U3-alternate             LTC1864IMS8#PBF           LTC1864IMS8#PBF-ND        13.57    * alt U3
PWB    Circuit Board    PWB-ADCMUX                                                           3.28

* alt U3 is Linear Technology LT1864, an 8 pin package. Its pin 1 is placed on the pwb's pad pin 2. Its command protocall is the same as the AD7685.
* Power Option: The SLIM-ADCMUX can be powered one of two ways:
1.  Application of +7.0 volts to +15 volts onto P16. The internal regulator will output +5 volts (+/- .1 v) onto P17. The voltage at P17 can then be used to power the final stage of the SLIM-PDM. This will assure that the PDM signal and the Analog to Digital Converter will have the same reference voltage. This assures maximum accuracy for VNA Phase measurements.
Or,
2.  The internal +5 volt regulator is not configured and a +5 volt source is applied to P17. For the MSA/VNA, The +5 volts at the final stage of the SLIM-PDM, P2, is used to supply power to P17. Do not install R16,C16,C17,C18, and U1
  In either case, this will assure that the PDM signal and the Analog to Digital Converter will have the same reference voltage. This assures maximum accuracy for VNA Phase measurements.
* Note for C6. The PWB-ADCMUX Rev 0 is missing component pads to accomodate C6. On the bottom of the board are pads to add the optional capacitors for each input. P3-2 is the common connection for use as an input to the ADC or as an output from the Mux. The capacitor on this point is C3.
  If the board is used as a Multiplexer + ADC (which replaces the original SLIM-ADC), then make R3 zero ohms and make C3 .001 ufd. That will satisfy the missing C6.

 The connections from the Control Board are:
        CB                  ADC-MUX
P3-2  (P3D0)   to     P11-2 (Sel A)
P3-3  (P3D1)   to     P10-2 (Sel B)
P3-4  (P3D2)   to     P9-2   (Sel C)
P3-1 Gnd         to     P9-1  Gnd
P3-8  (P3D6)    to     P8-2   (SERCLOCK)
P3-9  (P3D7)    to     P7-2   (CONVERT)
P25-4  (WAIT)   to     P6-2   (SERDATA)
P25-1 Gnd          to     P6-1  Gnd