# TMI3253S

**TMI** · DC-DC Converters · SOT-23-6

TMI3253S from TMI, in a SOT-23-6. 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 | BS | passive | Bootstrap. A capacitor connected between LX and BS pins is required to form a floating supply across the high-side switch driver. Absolute-maximum BS voltage is 26V; BS-to-LX max is 6V. |
| 2 | GND | power_in | Ground return pin for the IC and the low-side power MOSFET source. |
| 3 | FB | input | Output-voltage feedback input. Connect to the center tap of the external resistor divider. Regulated to VREF=0.6V typ (TMI3253S). Absolute maximum -0.3V to 6V. |
| 4 | EN | input | Enable input. Drive logic-high to enable the IC; drive logic-low to disable and enter micro-power shutdown. Do not float. EN rising threshold ~0.95V (0.85V-1.05V), 180mV hysteresis. Abs-max 20V. |
| 5 | IN | power_in | Power supply input. Operating range 4.5V to 18V; UVLO rising ~4.3V. Absolute maximum 20V. Bypass with a low-ESR ceramic capacitor (22µF typical) to GND. |
| 6 | LX | power_out | Switching node. Common drain of the integrated high-side and low-side power MOSFETs; connects to the external inductor. Abs-max -0.3V to 20V (-4.5V to 22V transient <10ns). |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | TMI |
| Package | SOT-23-6 |
| Category | PMIC |
| Pins | 6 |

## Ordering variants

Same part, different packaging or reel option.

- `TMI3253S`
- `TMI3253T`

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Input Supply Voltage, EN |  | -0.3 |  | 20 | V |  | 2 |
| LX Voltages |  | -0.3 |  | 20 | V |  | 2 |
| LX Voltages (<10ns transient) |  | -4.5 |  | 22 | V |  | 2 |
| FB Voltage |  | -0.3 |  | 6 | V |  | 2 |
| BS Voltage |  | -0.3 |  | 26 | V |  | 2 |
| BS to LX Voltage |  | -0.3 |  | 6 | V |  | 2 |
| Storage Temperature Range |  | -65 |  | 150 | °C |  | 2 |
| Voltage Range IN |  | 4.5 |  | 18 | V |  | 3 |
| TJ Operating Junction Temperature | TJ | -40 |  | 125 | °C |  | 3 |
| Input Voltage Range |  | 4.5 |  | 18 | V |  | 4 |
| OVP Threshold |  | 18.7 | 19.3 | 19.8 | V |  | 4 |
| Regulated Feedback Voltage (3253S) |  | 0.588 | 0.6 | 0.612 | V | TA=25°C,4.5V≤VIN≤18V | 4 |
| Shutdown Current |  |  | 5 | 10 | μA | VIN=12V, EN=0V | 4 |
| High-Side Switch Leakage Current |  |  | 1 | 10 | μA | VEN=0V, VLX=0V | 4 |
| Switch Valley Current Limit |  | 3.7 | 4 | 4.5 | A | Minimum Duty Cycle | 4 |
| On Time |  | 132 | 166 | 200 | ns | VIN=12V, VOUT=1.2V, IOUT=1A | 4 |
| Oscillation Frequency |  | 450 | 600 | 750 | kHz | Maximum Duty Cycle | 4 |
| Soft Start Time |  | 0.5 | 0.8 | 1.2 | ms |  | 4 |
| EN Rising Threshold |  | 0.85 | 0.95 | 1.05 | V |  | 4 |
| Absolute maximum Junction Temperature |  |  |  | 160 | °C |  | 2 |
| Power Dissipation |  |  |  | 1000 | mW |  | 2 |
| Lead Temperature (Soldering, 10s) |  |  |  | 260 | °C |  | 2 |
| UVLO Rising Threshold |  |  | 4.3 |  | V |  | 4 |
| UVLO Hysteresis |  |  | 0.35 |  | V |  | 4 |
| Quiescent Current |  |  | 300 |  | μA | VEN=2V, VFB=VREF x 105% | 4 |
| High-Side Switch On-Resistance |  |  | 70 |  | mΩ |  | 4 |
| Low-Side Switch On-Resistance |  |  | 35 |  | mΩ |  | 4 |
| Maximum Duty Cycle |  |  | 90 |  | % |  | 4 |
| Minimum On-Time |  |  | 80 |  | ns |  | 4 |
| Hiccup on Time |  |  | 1.2 |  | ms |  | 4 |
| Hiccup Time Before Restart |  |  | 3.6 |  | ms |  | 4 |
| EN Hysteresis |  |  | 180 |  | mV |  | 4 |
| Thermal Shutdown Threshold |  |  | 165 |  | °C |  | 4 |
| Thermal Shutdown Hysteresis |  |  | 30 |  | °C |  | 4 |
| Junction-to-ambient thermal resistance | θJA |  | 100 |  | °C/W |  | 3 |
| Junction-to-case(top) thermal resistance | θJC |  | 56 |  | °C/W |  | 3 |
| Junction-to-board thermal resistance | θJB |  | 16.2 |  | °C/W |  | 3 |
| Junction-to-case(top) characterization parameter | ψJC |  | 2 |  | °C/W |  | 3 |

## CAD (KiCad official)

- Symbol: `TMI3253S`
- Footprint: `Package_TO_SOT_SMD:SOT-23-6`
- 3D model: SOT-23-6 (KiCad packages3D, STEP)
- 3D model files: `tmi3253s-etched.step` / `tmi3253s-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `tmi3253s.step` / `tmi3253s.glb` are the bare package body.

## 3D model downloads

Two STEP files. Same geometry, different body top:

| File | Size | Use it when |
|---|---|---|
| [`tmi3253s.step`](tmi3253s.step) | 97 KB | You want the bare part, or you mark your own boards. |
| [`tmi3253s-etched.step`](tmi3253s-etched.step) | 1.8 MB | You want the part with `TMI3253S` already on it. |

The marking in the etched file is real recessed geometry cut into the solid, not a
texture or a decal: 445 faces against 117 in the bare model. It
survives export, section views, and rendering in any CAD tool, and it drops straight
into KiCad or Fusion with no extra setup.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [TMI datasheet](docs/tmi3253s-datasheet.pdf) (16 pp, sha256 `b58c2a4a18985f81`, 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/tmi3253s-datasheet.pdf)