# TMI3331

**TMI** · DC-DC Converters · ESOP-8

TMI3331 from TMI, in a ESOP-8. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | BS | power_in | High-side gate driver bias pin that supplies the high-side LDMOS gate driver, requiring a 100nF capacitor between BS and SW (absolute maximum BS-to-SW voltage is -0.3 to 6 V). |
| 2 | IN | power_in | Power input pin, with a recommended operating voltage range of 8 V to 30 V and an absolute maximum of 36 V for surge conditions. |
| 3 | SW | output | Switch pin that connects to the external inductor; the absolute maximum SW voltage is -0.3 to 36 V. |
| 4 | GND | power_in | Power ground pin for the converter. |
| 5 | FB | input | Output voltage feedback pin that regulates to an internal 0.8 V reference (784 mV to 816 mV), with input current limited to ±50 nA. |
| 6 | CS | input | Output current sense pin for constant current limit; the CC current is set by a resistor Rcs between CS and GND, giving ILIM = 61.7 mV / Rcs, and CS can be tied to GND to use the internal cycle-by-cycle peak current limit. |
| 7 | EN | input | Enable pin, with a logic high threshold of at least 1.5 V and a logic low threshold of at most 0.3 V. |
| 8 | FSW | input | Switching frequency set pin; a resistor sets the frequency from 130 kHz (floating) to 500 kHz (shorted to GND), with RFSW = 300 kΩ giving 310 kHz typical. |
| 9 | GND | power_in | Ground exposed pad that must be connected to the power ground copper area with copper and vias for heat dissipation and noise immunity. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | TMI |
| Package | ESOP-8 |
| Category | Power Management (PMIC) |
| Pins | 9 |

## 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 Voltage Range | VIN | 8 |  | 30 | V |  | 5 |
| Shut-down Current | ISD |  | 6 | 10 | uA | EN=0V | 5 |
| Standby Supply Current of TMI3331 | ISTBY |  | 10 | 15 | mA | VOUT=5V, No Load | 5 |
| Feedback Threshold Voltage | VFBTH | 784 | 800 | 816 | mV |  | 5 |
| FB Pin Input Current | IFB | -50 |  | 50 | nA |  | 5 |
| Input OVP Voltage | VINOVP | 31.5 |  |  | V |  | 5 |
| Output OVP Voltage | VOUTOVP |  | 10 | 20 | % |  | 5 |
| Input Voltage Range | VIN | 8 |  | 30 | V |  | 4 |
| Operating Junction Temperature Range | TJ | -40 |  | 125 | °C |  | 4 |
| IN, SW and EN Voltages |  | -0.3 |  | 36 | V |  | 3 |
| BS to SW Voltages |  | -0.3 |  | 6 | V |  | 3 |
| All other pins Voltage |  | -0.3 |  | 6 | V |  | 3 |
| Junction Temperature | TJ | -40 |  | 150 | °C | Note 2 | 3 |
| Storage Temperature |  | -65 |  | 150 | °C |  | 3 |
| Package Dissipation |  |  | 2 |  | W |  | 3 |
| Junction-to-ambient Thermal Resistance | θJA |  | 60 |  | °C/W |  | 3 |
| Junction-to-case Thermal Resistance | θJC |  | 46 |  | °C/W |  | 3 |
| Under Voltage Lockout | VUVLO |  | 7.2 |  | V | VIN rising | 5 |
| UVLO Hysteresis | VUVLO_HY |  | 0.6 |  | V |  | 5 |
| Quiescent Supply Current | ICCQ |  | 1 |  | mA | no load, VFB > 0.83V | 5 |
| Soft start Time | TSST |  | 4 |  | ms |  | 5 |
| CS Current Limit Voltage | VLIM_CS |  | 61.7 |  | mV |  | 5 |
| SW leakage | ISW_LEAK |  | 10 |  | uA |  | 5 |
| Maximum Duty Cycle | DDUTY |  | 90 |  | % | FS=300kHz | 5 |
| Switching Frequency | FS |  | 310 |  | kHz | RFSW=300kΩ | 5 |
| Switching Frequency | FS |  | 130 |  | kHz | FSW pin floating | 5 |
| Switching Frequency | FS |  | 500 |  | kHz | FSW short to GND | 5 |
| Switch On-Resistance (H side) | RON_HS |  | 80 |  | mΩ | By design | 5 |
| Switch On-Resistance (L side) | RON_LS |  | 60 |  | mΩ | By design | 5 |
| Short circuit Frequency | FSC |  | 35 |  | kHz | VFB=0V | 5 |
| Minimum Turn-on Time | TON_MIN |  | 200 |  | ns |  | 5 |
| EN High Level Input Voltage | VEN_H |  | 1.5 |  | V |  | 5 |
| EN Low Level Input Voltage | VEN_L |  | 0.3 |  | V |  | 5 |
| Thermal Shutdown Threshold | TSDN |  | 155 |  | °C | Note 3 (guaranteed by design) | 5 |
| Thermal Shutdown Hysteresis | TSDN_HY |  | 20 |  | °C | Note 3 (guaranteed by design) | 5 |

## Materials and finish

As the datasheet states them (page.json `metadata.appearance`; the 3D model's colours follow it).

| Part | Material | Colour / plating | Datasheet says | Page |
|---|---|---|---|---|
| contacts | copper |  | 3) Return FB to signal GND pin, and connect the signal GND to power GND at a single point for best noise immunity. Connect exposed pad to power ground copper area with copper and vias. | 8 |

## CAD (KiCad official)

- Symbol: `TMI3331`
- Footprint: `Package_SO:SOIC-8-1EP_3.9x4.9mm_P1.27mm_EP2.41x3.3mm`
- 3D model: ESOP-8 (KiCad packages3D, STEP)
- 3D model files: `tmi3331-etched.step` / `tmi3331-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `tmi3331.step` / `tmi3331.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [TMI datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8603008212798873600) (12 pp, sha256 `2839d7b5e08d9017`, retrieved 2026-10-18, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/tmi3331-datasheet.pdf)