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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 marked SL6SD in the FY1005S is, with high confidence, the SGMICRO SGM3204YN6G/TR. It is a SOT-23-6 inverting charge-pump DC/DC converter, not an EEPROM. The key reason is that SGMICRO’s official datasheet lists the package top-mark as “SL6XX”, where XX is the date/lot code; therefore SL6SD is a direct match. (sg-micro.com)

Detailed problem analysis

The identification is strongest from the manufacturer marking table, not from guesswork based on board function. In the SGM3204 datasheet, the ordering information for SGM3204YN6G/TR specifies SOT-23-6 package marking SL6XX. That means the first three characters, SL6, identify the device family, while the last two characters vary with production code. Your observed marking SL6SD therefore fits the official marking convention exactly. (sg-micro.com)

Electrically, the SGM3204 is an unregulated charge-pump voltage inverter. Its datasheet specifies 1.4 V to 5.5 V input, output approximately equal to \(-V_{IN}\), up to 200 mA output current, and a typical 950 kHz switching frequency. It also shows the required external network: one flying capacitor plus input and output capacitors, which is the standard architecture for a negative-rail generator. (sg-micro.com)

The official pinout is also consistent with what you would expect on a small negative-supply generator: pin 1 = OUT, pin 2 = IN, pin 3 = CFLY-, pin 4 = GND, pin 5 = EN, pin 6 = CFLY+. So if you probe the board and find one pin at about +5 V, one at 0 V, and one near -5 V, that is a strong functional confirmation that U2 is indeed the SGM3204. (sg-micro.com)

For the FY1005S specifically, the most plausible role of this IC is to generate a small negative analog rail for the output amplifier stage. That conclusion is an engineering inference, because a full official FY1005S schematic is not readily available, but it is consistent with community teardown/repair reports and with the SGM3204’s intended application category, which includes bipolar amplifier supply. (elektroda.com)

This also means some alternative identifications are very likely incorrect. An EEPROM interpretation does not match the official SL6XX marking or the SGM3204 package/function data, and a buck regulator interpretation conflicts with the fact that the SGM3204 is explicitly a charge-pump inverter whose reference application uses capacitors rather than an inductor. (sg-micro.com)

Current information and trends

As of March 15, 2026, SGMICRO still lists the SGM3204YN6G/TR as an active product on its product page, so it remains a valid replacement target rather than an obsolete legacy part. (sg-micro.com)

From a design perspective, using a small charge pump to generate a modest negative rail from a single positive supply is still common in low-cost mixed-signal instruments, especially where the analog output stage benefits from headroom below ground without the cost and EMI burden of a larger inductive supply. The SGM3204 product page explicitly positions it for bipolar amplifier supply use. (sg-micro.com)

Supporting explanations and details

A practical sanity check on the bench is:

  • Pin 2 (IN): about +5 V
  • Pin 4 (GND): 0 V
  • Pin 1 (OUT): typically near -5 V at light load
  • Pin 5 (EN): logic high to enable operation
  • Pins 3 and 6: connected to the flying capacitor (sg-micro.com)

If you are replacing it, the exact part designation to look for is SGM3204YN6G/TR, package SOT-23-6. (sg-micro.com)

Ethical and legal aspects

There are no unusual legal issues here, but normal repair discipline applies: use ESD precautions, observe polarity/orientation carefully, and do not substitute an arbitrary 5/6-pin device solely from the top mark because short SMD markings are often reused across unrelated IC families. The reason this case is different is that the official marking table gives a direct match. (sg-micro.com)

Practical guidelines

To verify on your specific board:

  • Confirm that U2 has 6 pins, not 5 or 8. (sg-micro.com)
  • Check whether it is surrounded mainly by small ceramic capacitors, consistent with a charge pump. (sg-micro.com)
  • Measure for a negative output rail on pin 1. (sg-micro.com)

If U2 has failed, also inspect the downstream analog stage, because overload or accidental external voltage injection at the generator output can damage both the negative-rail generator and the amplifier it powers. That part is a general repair caution and an engineering inference rather than a manufacturer-stated FY1005S service note. (elektroda.com)

Possible disclaimers or additional notes

The answer is very likely correct, but I would still phrase it as “almost certainly SGM3204” unless you confirm the package and a few pin voltages on your own board. FY1005S units can have minor PCB revision differences, and low-cost instruments do not always have a stable BOM across production runs. (elektroda.com)

Suggestions for further research

If you want, the next useful step would be to identify:

  • the three capacitors around U2,
  • the negative rail voltage actually present,
  • and the output op-amp that U2 is feeding. (sg-micro.com)

That would fully confirm the power-tree function and help if your purpose is repair rather than identification. (elektroda.com)

Brief summary

U2 with top mark SL6SD in the FY1005S is almost certainly the SGMICRO SGM3204YN6G/TR, a 6-pin inverting charge-pump converter used to generate a negative supply rail. The decisive evidence is the official SGMICRO marking code SL6XX, which matches SL6SD exactly. (sg-micro.com)

If you want, I can also give you the pin-by-pin test procedure for checking U2 in-circuit with a multimeter.

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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