Unconnected Pins Analysis

flux

Here’s what I found regarding unconnected pins and whether any require pull-up/pull-down resistors.
Summary of findings

Table

ComponentUnconnected pins foundDatasheet requirementPull-up/down required?Recommended action
U1 ADM7150ARDZ-5.0VREG, BYP, REF appear unconnected. REF_SENSE is currently tied to +5V (VOUT).ADM7150 requires local bypassing on internal nodes and specific referencing: BYP -> ~1 µF to GND; VREG -> ~10 µF to GND; REF -> ~1 µF to GND; REF_SENSE must be connected to REF (not to VOUT). Source: TI/ADI ADM7150 datasheet (see links below).No. These are not digital I/O; they require capacitors and correct referencing, not pull resistors.- Add caps: BYP ≈ 1 µF to GND; VREG ≈ 10 µF to GND; REF ≈ 1 µF to GND. - Re-route REF_SENSE to REF (remove tie to +5V). - EN has no internal pull; your design ties EN to VIN (via +5V), which is acceptable.
U3 LM4811MM/NOPBBYPASS, CLOCK, UP/DN, SD are unconnected.LM4811 datasheet: BYPASS pin needs a capacitor (~1 µF recommended) to GND to minimize pops. SD must be tied to a fixed voltage (GND to enable, VDD for shutdown). The datasheet does not state internal pulls on CLOCK/UP-DN/SD; do not leave them floating.Not strictly required as “pull” resistors; the requirement is “tie to a fixed logic level.”- Add BYPASS cap (~1 µF) to GND. - Tie SD to a defined level (GND to run or VDD to keep in shutdown). - If volume control isn’t used, tie CLOCK to GND and tie UP/DN to a defined logic level so it cannot float.
U5 TLV70030DCKTNC (pin 4) is unconnected.TLV700 datasheet: NC can be left floating; may be tied to GND to improve thermal dissipation. EN has defined thresholds; no internal pull specified; if shutdown not used, EN may be tied to IN.No.- Leaving NC floating is OK (optional: tie to GND). - Your EN is already tied to +5V/IN, which is fine.
U2 TLV9064/TLV9164None (all op-amp pins are on nets).N/AN/ANo action needed.
Key datasheet evidence
  • LM4811 (U3)
    • BYPASS capacitor requirement and placement; SD must be tied to a fixed voltage; CLOCK/UP-DN logic thresholds and no mention of internal pulls. Per LM4811 datasheet (excerpts retrieved): “This is the BYPASS pin capacitor… CB equal to 1 µF or larger is recommended…”; “the SHUTDOWN pin should be tied to a fixed voltage to avoid unwanted state changes.”; “trigger point is 1.4 V min high, 0.4 V max low” for CLOCK and UP/DN.
  • ADM7150 (U1)
  • TLV70030 (U5)
    • NC = no connection (optionally tie to GND); EN thresholds; EN can be tied to IN if always on; no specified internal pull. Datasheet: https://www.ti.com/lit/gpn/tlv700
Conclusions
  • None of the unconnected pins in this design require pull-up or pull-down resistors per se.
  • However, several unconnected pins do require defined connections per their datasheets:
    • U1: add the required bypass capacitors on BYP, VREG, and REF, and tie REF_SENSE to REF (not to +5V).
    • U3: add BYPASS capacitor; tie SD, CLOCK, and UP/DN to defined logic levels (do not leave floating).
    • U5: NC can remain floating; EN is already properly tied high.
Would you like me to implement these fixes (add the capacitors, tie the control pins to defined rails, and correct U1’s REF_SENSE wiring)? If yes, tell me your desired default for U3’s SD (run or shutdown) and UP/DN (default up or down), and I’ll set them accordingly.
Tie LM4811 control pins
Fix ADM7150 bypass pins
Add datasheets to parts
Select cap values/footprints
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Properties

flowchart LR VBAT[9V Battery] --> SW1[Power Switch] SW1 --> D1[SS14 Reverse Polarity] D1 --> CIN[Input Bulk/RC Filter<br/>47uF + 2.2Ω + 10uF] CIN --> LDO[ADM7150 5.0V LDO] LDO --> V5[+5V Rail] V5 --> U2[TLV9064 Quad OpAmp] V5 --> MIC1[MAX4466 Mic Module 1] V5 --> MIC2[MAX4466 Mic Module 2] V5 --> MIC3[MAX4466 Mic Module 3] V5 --> MIC4[MAX4466 Mic Module 4] V5 --> DIV[VREF Divider 10k/10k] DIV --> BUF[U2A VREF Buffer] BUF --> VREF[VREF = 2.5V (filtered)] MIC1 --> AC1[AC Couple + RIN] MIC2 --> AC2[AC Couple + RIN] MIC3 --> AC3[AC Couple + RIN] MIC4 --> AC4[AC Couple + RIN] AC1 --> SUM[U2B Active Summing Mixer] AC2 --> SUM AC3 --> SUM AC4 --> SUM VREF --> SUM SUM --> HPF[High-Pass ~200Hz<br/>82nF + 10k to VREF] HPF --> VOL[Master Volume A10k<br/>top=HPF bottom=VREF] VOL --> BUF2[U2C Output Buffer] BUF2 --> OUTTS[6.35mm TS Output<br/>100Ω + 10uF + 100k bleed] BUF2 --> OUTUHF[3.5mm TRS UHF LINE Output<br/>10k trim + 100Ω + 10uF + 100k bleed]

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