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SGMICRO SGM3204 SL6SD IC in FY1005S Signal Generator – Function and Identification

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User question

What is the integrated circuit U2 with markings SL6SD in the signal generator model FY1005S ?

Artificial Intelligence Response

Direct answer to the question

  • U2 with top‑mark “SL6SD” on the FY1005S is the SGMICRO SGM3204 (full P/N: SGM3204YN6G/TR), a 200 mA inverting charge‑pump DC/DC converter used to generate a negative supply rail (≈ −5 V) from the +5 V input. The SGM3204 SOT‑23‑6 package marking is “SL6XX”; your “SL6SD” corresponds to “SL6” plus a two‑character date/lot code. (sg-micro.com)

  • The FY1005S module is powered from 5 V; U2 creates the small negative rail needed by the output/analog stages. (sainsmart.com)

Detailed problem analysis

  • Role in the FY1005S power tree:
    • External supply: +5 V (wall adapter shipped with some FY1005S/UDB1005S kits). (sainsmart.com)
    • Digital rail(s): +3.3 V (from a separate regulator, typically an LDO/buck not related to U2).
    • Analog rail(s): U2 (SGM3204) inverts +5 V to approximately −5 V (under load the magnitude is slightly less), supplying the output amplifier and any analog front‑end that benefits from headroom below ground.
  • How we know “SL6SD” = SGM3204:
    • The SGM3204 datasheet explicitly states the SOT‑23‑6 top‑mark is “SL6XX” (XX = date code). Your device’s “SL6SD” matches this scheme. (sg-micro.com)
    • Third‑party component listings show SGM3204YN6G/TR in SOT‑23‑6 with silk/mark “SL6SD,” aligning with the datasheet’s “SL6 + date code” convention. (tao.hooos.com)
  • Device characteristics relevant to the FY1005S:
    • Input 1.4–5.5 V, inverts to −VIN (unregulated), up to 200 mA, ~950 kHz switching. Package SOT‑23‑6. Pinout: 1‑OUT, 2‑IN, 3‑CFLY−, 4‑GND, 5‑EN, 6‑CFLY+. (sg-micro.com)
  • Why an inverting charge pump (not a buck/LDO/logic gate)?
    • The FY1005S runs from +5 V; it still needs a small negative rail to let the output driver swing cleanly around 0 V and handle DC offset range without clipping. A compact, low‑cost charge pump (no inductor) is the canonical solution for −5 V at tens to low‑hundreds of mA. The SGM3204 matches the packaging, marking, and function. (sg-micro.com)

Current information and trends

  • Modern DDS/function‑generator modules commonly derive a negative analog rail from a +5 V source using inverting charge‑pump ICs (e.g., SGM3204, MAX660/ICL7660 families) to avoid inductors and save space/cost; higher‑frequency devices (≈1 MHz like SGM3204) help push switching noise out of the audio band. (sg-micro.com)

Supporting explanations and details

  • Quick functional checks on the board (with +5 V applied):
    • U2 pin 2 (IN) ≈ +5 V; pin 4 (GND) = 0 V; pin 1 (OUT) ≈ −4.4…−5.0 V no‑load; pin 5 (EN) high (>1.5 V) to enable; pins 3/6 connect to the flying capacitor. If OUT is near 0 V or positive, the IC is disabled, damaged, or output is shorted. (sg-micro.com)
  • Typical external parts around U2:
    • Three ceramics (often 3.3–10 µF): CIN from IN‑to‑GND, CFLY between CFLY+ and CFLY−, COUT from OUT‑to‑GND. Layout should keep these loop areas tight to minimize ripple/noise. (sg-micro.com)

Ethical and legal aspects

  • Use genuine parts conforming to RoHS/HSF and observe ESD/handling precautions per the manufacturer documentation to avoid latent damage and ensure safety. (sg-micro.com)

Practical guidelines

  • Confirm identification:
    • Visually verify SOT‑23‑6 and “SL6xx” mark, then measure the −V rail at U2 pin 1.
  • Replacement/repair:
    • Direct replacement: SGM3204YN6G/TR, match SOT‑23‑6 footprint.
    • Check/replace the three capacitors (CIN, CFLY, COUT); damaged or low‑ESR mismatch can cause excessive ripple or stress the IC.
    • Verify EN (pin 5) is driven high; if EN is low, OUT will be 0 V. (sg-micro.com)
  • Noise considerations:
    • Although the SGM3204’s ~950 kHz operation is well above the audio band, poor grounding/layout can couple switching ripple into the output. Keep loop areas small and provide solid analog ground returns. (sg-micro.com)

Possible disclaimers or additional notes

  • Some FY1005S variants may use functionally similar inverters from other vendors, but the “SL6XX” top‑mark uniquely matches SGM3204’s official marking. If your board’s behavior differs (e.g., VIN ≠ 5 V, or U2 pinout not as above), supply a macro photo and measurements to confirm. (sg-micro.com)

Suggestions for further research

  • If you intend to improve PSU performance or reduce ripple, compare SGM3204 with alternatives (e.g., higher‑current charge pumps or inductive inverters) and evaluate output noise on the analog path.
  • Review the SGM3204 layout guidance in the datasheet and audit the FY1005S board for best practices. (sg-micro.com)

Brief summary

  • U2 “SL6SD” on the FY1005S is SGMICRO’s SGM3204 inverting charge‑pump converter. It generates the −5 V rail from the +5 V supply used by the module. The “SL6SD” string is the official “SL6” device code plus a date/lot code, which the SGM3204 datasheet confirms. Replace with SGM3204YN6G/TR and verify the three capacitors and EN pin if you are repairing the unit. (sg-micro.com)

User question

What are the values of the capacitors C4,C5 and C13 on the signal generator FY1005S ?

Artificial Intelligence Response

Direct answer to the question

  • There is no publicly available schematic or bill of materials for the FY1005S that lists the values of C4, C5, and C13. Retail and manual pages for the FY1005S (and related FYxxxxS series) do not publish component values. (uniqkart.in)
  • On many FY1005S boards, these three capacitors are physically clustered around U2 (an inverting charge‑pump IC commonly marked “SL6xx,” i.e., SGMICRO SGM3204). If C4, C5, and C13 are indeed the input bypass, flying, and output capacitors of that inverter, the SGM3204 datasheet recommends 3.3 µF ceramic for all three (CIN, CFLY, COUT). Typical workable values in practice are 3.3–10 µF X7R. (static6.arrow.com)

Key points

  • Exact values may differ between board revisions; designators can move across revisions.
  • If you can confirm these three caps sit on the SGM3204 pins (IN, CFLY±, OUT), use 3.3 µF X7R (≥10–16 V rating) as the correct value per datasheet; 4.7–10 µF also works and can reduce ripple. (static6.arrow.com)

Detailed problem analysis

  • Why the ambiguity: FY1005S is a low‑cost DDS/FPGA-based function generator whose vendors provide marketing specs but no service schematics or BOM. That means silkscreen designators (C4, C5, C13) are not standardized across production runs, and owners see different placements/values across revisions. (uniqkart.in)
  • Likely circuit role of C4, C5, C13: The module needs a small negative rail (about −5 V) for its output amplifier. Most FY1005S boards generate this with an unregulated inverting charge pump (SGM3204 in SOT‑23‑6; common topmark “SL6xx”). The SGM3204 requires:
    • CIN from IN to GND
    • CFLY between CFLY+ and CFLY−
    • COUT from OUT to GND The datasheet “Typical Application” shows CIN = CFLY = COUT = 3.3 µF; performance plots also document experiments with 1 µF, 3.3 µF, 4.7 µF, and 10 µF, confirming that 3.3–10 µF X7R is the intended range. (static6.arrow.com)
  • Practical implication: If your board’s C4, C5, C13 are those three parts, using matched ceramics (3.3–10 µF, X7R, 0603–0805, ≥10–16 V rating) is technically sound and aligns with the IC vendor’s guidance. Larger values can slightly reduce output ripple at the cost of inrush and size; the datasheet shows ripple reduction as capacitance increases. (static6.arrow.com)
  • Caveat: If any of C4, C5, C13 are elsewhere (e.g., op‑amp compensation, crystal load, output coupling), their values will be very different (pF–nF for compensation or crystal; 1–10 µF for coupling). Visual confirmation is essential before committing.

Current information and trends

  • As of November 2021 (datasheet Rev. A) and current distributor pages, SGM3204 remains an active part with the same recommended external network (CIN = CFLY = COUT = 3.3 µF). This is consistent with what you should expect to find on a −5 V inverter in recent low‑cost function generators. (static6.arrow.com)
  • Vendor and reseller listings for FY1005S (accessed in late 2025) still do not provide schematics or per‑designator values, so field identification remains the practical route. (uniqkart.in)

Supporting explanations and details

  • Identifying the three caps:
    • Find U2 (SOT‑23‑6). If topmark begins “SL6…”, that matches SGM3204. The pins to locate:
    • Pin 2 (IN): should have a bypass cap (CIN) to GND.
    • Pins 6 and 3 (CFLY+, CFLY−): a single “flying” cap (CFLY) between them.
    • Pin 1 (OUT): should have an output cap (COUT) to GND.
    • If C4, C5, C13 coincide with those roles, they should all be 3.3–10 µF ceramic. (static6.arrow.com)
  • Verifications:
    • With power applied, IN ≈ +5 V (or your board’s main rail), OUT ≈ −VIN (unregulated), typically −4.5 to −5 V at light load. Ripple should decrease with higher COUT/CFLY/CIN. (static6.arrow.com)

Ethical and legal aspects

  • Safety: Power down, disconnect the supply, and discharge capacitors before measuring/removing components. Observe ESD handling around the DDS/FPGA and op‑amps. Follow general repair safety norms.

Practical guidelines

  • If repairing without exact values:
    • Use three identical X7R ceramics, 3.3 µF to 10 µF, 16 V rating (or ≥10 V minimum), size 0603–0805 to fit pads.
    • Prioritize low‑DC‑bias parts (X7R over Y5V/Z5U) to avoid capacitance loss at 5 V bias.
    • After replacement, verify:
    • −5 V rail magnitude at U2 pin 1,
    • Rail ripple at 1 mA–100 mA load,
    • Output amplifier headroom/noise on the main output.
    • If any of the three is not on U2, stop and map the net with continuity mode before choosing values (pF–nF parts are common around op‑amp feedback and crystal networks).
  • Best practices:
    • Replace in matched sets for CIN/CFLY/COUT to maintain balanced performance.
    • Keep leads short; place capacitors as close as possible to U2 pins to minimize ESR/ESL.
    • Use ≥50 V parts only where physically larger tantalum/electrolytic were originally used (unlikely for this inverter).

Possible disclaimers or additional notes

  • Board-to-board variation is real on low‑cost instruments; designators can move. Without a photo of your specific PCB, any numeric assignment of C4/C5/C13 is an inference based on common layouts and the SGM3204 datasheet. (static6.arrow.com)

Suggestions for further research

  • If you can share clear photos (both sides) showing C4, C5, C13 relative to U2 and the BNC/output amp, I can confirm functions and advise precise values.
  • If C13 is part of the output path (coupling or RC shaping), we can compute a value from the output impedance and desired low‑frequency cutoff.
  • Keep an eye on community teardowns; to date, reseller pages and generic manuals still omit per‑designator values. (uniqkart.in)

Brief summary

  • No official FY1005S BOM lists C4, C5, C13 values publicly. If those three are the SGM3204 inverter’s CIN, CFLY, COUT, the correct value per the IC vendor is 3.3 µF each (X7R ceramic; 3.3–10 µF acceptable). Please share PCB photos to verify their exact role on your board so we can confirm the numbers with certainty. (static6.arrow.com)

If you can upload a photo or tell me what C4, C5, and C13 connect to (which IC pins/nets), I’ll map each one for your exact board and provide definitive values.

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