TX4138

@@ -0,0 +1,48 @@+# TX4138++**XDS** · DC-DC Converters · SOIC-8-EP++TX4138 from XDS, in a SOIC-8-EP. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | SW | output | Switch node output. Source of the internal high-side power MOSFET; connect this pin to the switching end of the inductor and to the cathode of the external freewheeling Schottky diode. Absolute maximum: -0.3V to VIN + 0.3V. |+| 2 | ILIM | power_in | Programmable maximum peak current pin. Power current flows into the chip through an external accurate sense resistor connected between ILIM and VIN; the sense resistor value (~15-30mΩ) sets the peak current limit (30mΩ for 2A, 20mΩ for 3A, 15mΩ for 4A). Internally tied to the power MOSFET, so heat dissipation on this pin matters. Absolute maximum: 62V. |+| 3 | VIN | power_in | Supply voltage input, 4.5V to 60V unregulated. Also the drain of the internal high-side power MOSFET and power supply for the whole chip. A local input capacitor (CIN) placed as close to the IC as possible is required to prevent large voltage spikes. Absolute maximum: 62V. |+| 4 | GND | power_in | Ground return and voltage reference for the regulated output. Should be routed carefully outside the D1-to-CIN high-current ground path to prevent switching current spikes from injecting noise into the part. |+| 5 | FB | input | Feedback input to the error amplifier. An external resistor divider from VOUT to GND, tapped to FB, sets the output voltage; reference is 0.805V (typ, 0.785-0.825V). When FB falls below 250mV a frequency-fold-back comparator reduces oscillator frequency to prevent short-circuit current-limit runaway. Bias current ~10nA. Absolute maximum: -0.3V to +6.5V. |+| 6 | EN | input | Enable input. Drive low to disable (turn off) the chip; leave floating (or drive high) to enable. Absolute maximum: -0.3V to +6.5V. |+| 7 | POK | output | Power-good open-drain output. Pulled low while FB is less than 90% of the 0.8V reference; goes high-Z when output is in regulation. Requires an external pull-up (e.g. 10kΩ) to a system rail up to 45V; can also drive the enable pin of a downstream converter. Tie to GND or leave floating if unused. Absolute maximum: 0V to 45V. |+| 8 | BS | passive | Bootstrap capacitor pin. Provides the positive supply rail for the high-side MOSFET gate driver (VBST - VSW = 6V typ). Connect a 100nF ceramic capacitor and a series ~5-10Ω resistor between BS and SW. Absolute maximum: VSW + 6.0V. |+| 9 | ILIM (EP) | power_in | Exposed thermal pad, internally connected to the ILIM node (same net as pin 2). Provides the primary heat-dissipation path for the internal power MOSFET and must be soldered to a copper pour that also carries the ILIM/sense-resistor current back to VIN. |++## Key specifications++| Parameter | Value |+|---|---|+| Manufacturer | XDS |+| Package | SOIC-8-EP |+| Category | PMIC |+| Pins | 9 |++## Ordering variants++- `TX4138`++## CAD (KiCad official)++- Symbol: `TX4138`+- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`+- 3D model: SOIC-8-EP (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [XDS datasheet](docs/tx4138-datasheet.pdf) (7 pp, sha256 `cd9a50cd55184667`, retrieved 2026-08-17, tier: lcsc)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/tx4138-datasheet.pdf)

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