Chapter 4: 31
4.4.8.3 Breakout Board schematic (061-0179-00)
Page 1: The Power/Status LED signal arrives on J1 pin 13 and then connects to D1
anode. The white LED signal arrives on J1 pin 9 and then connects to J6 pin 1.
4.4.9 Battery Simulator Circuits
4.4.9.1 Chamber Board Schematic (061-x178-0x)
Page 4: U1 pin 9 outputs a voltage of from 0 to 2.5V. R35 and R36 divide this voltage
down to from 0 to 1.5V and connect it to the non-inverting input of U8-A.
U8-A then buffers this voltage and sends it on toward the battery pill. R31
and D2 provide some current limiting protection to the hearing aid and pre-
vent negative transients during power on. The battery current passes through
the current sense resistor R50, or through J10 pin 6 to the 25.5ohm resistor on
the breakout board. The voltage at the high side of the current sense resistor is
sampled via R82 or pin 12 of J10 and connected to one end of the digital pot
J7-A, and also to the amplifier U11-A. The output of the amplifier then con-
nects to ADC0 on pin 61 of U1-C. The voltage at the low side of the current
sense resistor R50, or via pin J10 pin 7 to the sense resistor on the Breakout
Board, is also sampled and connected to the other end of the digital pot J7-A,
and also to the amplifier U9-A. The output of this amplifier then connects to
ADC1 on pin 62 of U1-C. U11-A and U9-A amplify the difference between the
voltage at the DAC1 output on pin 10 of U1-C, and the sense voltages at their
non-inverting inputs by three times. The low side of sense resistor R50 also
connects to J8 pin T3. The pill type pull up resistor R41 or R60 works with
the pill type resistor in the battery pill either through J8 pin R2, or J10 pin 11,
to produce a voltage which is buffered by U9-B and then fed to ADC2 on pin
63 of U1-C.
4.4.9.2 Breakout Board Schematic (061-0179-01)
Page 1: The battery current arrives on J1 pin 6 and then connected to the sense resis-
tor R2. The voltage on the high side of the sense resistor is sampled and sent
back to the Chamberboard on J1 pin 12. The voltage on the low side of the
sense resistor is sampled and sent back to the Chamberboard on J1 pin 7. The
battery current is then sent to J2 pin T5. The connection from the pill type
resistor on the battery pill is connected from J2 pin R2 to J1 pin 11.
4.4.10 Thermal Printer Circuits
4.4.10.1 Parallel Interface Board (061-0500-0x)
The parallel interface printer data arrives from the SBC at J2. It then leaves to the Printer
Interface Board at J1.
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