Analog to Digital
4-30-08. Update page for name changes.
No pwb or schematic changes.
7-14-08. Parts list revised for incorrect
switch (SW1, SW2) part number.
8-11-09. Add explanation for Optional Power
Modification when used with MSA/VNA
5-17-15. Parts list revised to Rev B and moved
to this page. Change capacitors for new builds. Working units need not
AtoD Converter, 16 bit, size
Use your mouse's "right click" and "Save Link" to download
the current versions:
Schematic, in ExpressPCB software.
artwork for PWB, in ExpressPCB software.
Use this drawing to order the pwb from Express, or use as
Layout to locate
the parts on the SLIM-ADC-16.
c. PLSLIM-ADC-16 Rev B. Parts List. Maintained on this
Download the AD7685 data sheet at:
Part #: SLIM-ADC-16 Rev 0, Released
Schematic: SKSLIM-ADC-16 Rev 0,
Parts List: PLSLIM-ADC-16 Rev A,
PWB: PWB-ADC10 Rev 0, Released
The SLIM-ADC-16 is a dual 16 bit, serial,
analog to digital
AD7685's. There is no manual adjustment to set the A to D
range. It is not needed to obtain excellent resolution in the
MSA and VNA systems. Each AtoD will digitize its
of 0 to 5 volts to a bit value of 0 to 65535 bits. This
to 76.3 uv per bit.
Both A/D's will
capture, and clock out their
data simultaineously. The
software commands both U2 and
begin conversion with a single toggle of the signal, "CONVERT".
16 toggles of the signal, "SERCLOCK", causes the I.C. to
output a serial stream of
16 bits. The serial SDO outputs of the AtoD I.C.'s
limited (500 ua) current
capability. Therefore, the open collectors of Q1 and Q2 provide
buffering and current
drive the "WAIT" and "ACK" lines to the LPT port of the
Computer. The Computer's LPT port
is nominally a TTL compatible input with a pull up resistor to
+5 volts. It can also drive a pull-up on a +3.3v bus.
5-17-15 For new builds, Q1 and Q2 are called
out as 2N7002, FETs. This allows higher data transfer speeds.
The circuit is designed with thru hole pads, to
allow each input to be connected
to an external switch. The switch selects the amount of capacitance to
be placed in shunt with the
input. Each switch is a single pole, three throw, with a
non-connecting center position. This allows a selection of
different integration times (Video Bandwidth). This module is
expected to be mounted very close to the front panel of the integrated
system so that the user can mount the switches on the front panel and
maintain very short leads from the switches to the bottom of the module.
The base PWB has the part number,
PWB-ADC10. The "10" signifies the use of a 10 pin MSOP
package. There are other A/D I.C.s with this package. More
A/D SLIMs could be created from this pwb design. For
the Basic MSA, only the U2 section needs to be populated. The U3
section is used for the VNA extension of the MSA.
Optional Power Modification to SLIM-ADC-16 when used in the MSA with VNA
This optional modification allows the SLIM-ADC-16 to
be powered directly by the Phase Detector Module's regulated +5
causes both modules to use the same regulated +5 volts. This
results in more accurate Phase Measurements with the VNA.
The modification is quite simple: Remove and delete
U1, the 78L05. Jumper a wire between the two pads that supported
U1. The pads are U1 pin 3, to U1 pin 1. The power input at
P1 pin 2 must be +5 volts, which is provided by the Phase Detector
SKSLIM-ADC-16, Schematic of