12B/18/7 Series
Service Manual
2-4
Table 2-2. U1 Pinout Table
Pin No. Pin Name Description
1 READ (L) When low (VSS), data from addressed register can be read
2 ADR5 Most significant address bus line
3 ADR4 Bit 4 of parallel address bus
4 ADR3 Bit 3 of parallel address bus
5 ADR2 Bit 2 of parallel address bus
6 ADR1 Bit 1 of parallel address bus
7 ADR0 Least significant address bus line
8 VSS Negative power supply voltage (-3V relative to DGND)
9 VDD Positive power supply voltage for analog only (Vbat-3V=VDD-DGND)
10 K0 1st a/d gain resistor pin, generally for de-integrate
11 K1 2nd a/d gain resistor pin, generally for integrate
12 K2 3rd a/d gain resistor pin, for autozero
13 AZ A/D converter pin for autozero capacitor
14 INT A/D converter pin for integrator capacitor
15 REFI 1.00V reference voltage for de-integrate signal in volts
16 BIAS Pin for analog bias current generator reference resistor
17 REFH Connects 1.235V reference voltage to on-chip circuits
18 BGND Not used
19 AFO Active filter high output pin (2-pole, low-pass filter)
20 FAO Internal active filter node
21 FAI Internal active filter node
22 AFI Active filter high input pin
23 VSS Negative power supply voltage (-3V relative to DGND)
24 PFO Passive filter low output pin (1-pole, low-pass filter)
25 AVAOM Absolute value amp (full wave rectified) negative output pin
26 AVAOP Absolute value amp (full wave rectified) positive output pin
27 AVAM Absolute value amp inverting input (summing node)
28 ACBO AC buffer output
29 VSET Voltage divider sense for power supply
30 PSTEST Pin to disable on-chip power supply for U1 testing
31 DGND Ground power supply pin connected to common (digital ground)
32 AGND Common input sense line. No current flow (analog ground).
33 CLAMP Op amp output voltage for Q2 clamp transistor base drive
34 AMPS Shunt resistor sense pin. Unused in Fluke Model 18.
35 ISRC Current source pin for continuity, ohms, and capacitance
36 SWS Slide-switch position sense pin. Internal pull down.
37 OHMS Ohms sense resistor input pin. Sense voltage at J2.
38 VSS Negative power supply voltage (-3V relative to DGND)
39 ACV AC volts input pin from 10 MΩ resistor
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