STMicroelectronics STTH208U

Overview

STTH208U from STMicroelectronics is an ultrafast recovery silicon rectifier diode in SMB package, rated for 2 A average forward current and 800 V repetitive peak reverse voltage, with 75 ns maximum reverse recovery time and 0.89 V typical forward voltage at 150 °C - used as a freewheeling or snubber diode in offline SMPS and PFC stages.

For engineers reviewing the STTH208U datasheet, STTH208U pinout, STTH208U application, or STTH208U equivalent, key selection criteria include soft-switching EMI performance, thermal resistance (R_th(j-l) = 25 °C/W), surge capability (I_FSM = 45 A), and ECOPACK-compliant lead-free SMB packaging.

Technical Context

This diode employs ST's planar ultrafast high-voltage technology to achieve low Q_rr and soft reverse recovery, minimizing switching losses and voltage overshoot in hard-switched topologies. Its 175 °C maximum junction temperature and 25 °C/W junction-to-lead thermal resistance support high-power-density designs without forced cooling.

The device operates with controlled minority-carrier lifetime to balance trr, VF, and softness - enabling use in 50–100 kHz flyback and boost converters where fast but non-oscillatory turn-off is critical for EMI compliance and MOSFET stress reduction.

Key Specifications

Pinout & Package

SMB (DO-214AA) surface-mount package: 2-terminal, gull-wing leads, 3.3–3.95 mm width, 5.1–5.6 mm length, 1.9–2.45 mm height; RoHS-compliant, UL94 V0 epoxy, lead-free.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultrafast recovery diode applications.

Compared with STTH2R08 and ES2J, STTH208U uniquely balances 75 ns trr, 0.89 V VF, and 25 °C/W thermal resistance in SMB format - making it optimal for cost-sensitive, thermally constrained 50–100 kHz offline power supplies.

Availability

STTH208U is available at Aetrix Electronics and suitable for offline AC-DC adapters, boost PFC front-ends, and snubber networks requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for STTH208U includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The STTH series targets high-efficiency, high-reliability power conversion - specifically engineered for ultrafast recovery in 50–200 kHz switching applications where softness, thermal robustness, and voltage ruggedness are critical.

FAQ

What is the maximum allowable junction temperature for STTH208U?

The absolute maximum junction temperature is +175 °C, verified per datasheet Table 1. This rating applies under steady-state conditions with proper PCB copper area and lead thermal coupling. Derating is required above 125 °C ambient, and thermal design must ensure R_th(j-a) remains within 110 °C/W (SMB, no copper) or lower with heatsinking.

Does STTH208U have a specified reverse recovery charge (Qrr)?

Q_rr is not explicitly listed in DS3068 Rev 2, but can be estimated from trr = 75 ns, I_F = 0.5 A, and I_rr = 0.25 A test conditions in Table 4. Using Q_rr ≈ 0.5 × I_rr × t_rr, typical Q_rr is ~9.4 nC - consistent with ultrafast diodes optimized for low EMI in flyback and PFC circuits.

Can STTH208U replace a standard FR107 diode in a 24 V input buck converter?

No - FR107 is rated for 1000 V VRRM but has trr ≈ 500 ns and VF ≈ 1.3 V. STTH208U offers superior speed and lower VF but only 800 V rating. For 24 V systems, its voltage margin is excessive and unnecessary; a 200 V ultrafast diode like STTH1R02 would be more appropriate and cost-effective.

Is the STTH208U SMB package compatible with standard reflow profiles?

Yes - the lead-free SMB package is qualified for JEDEC J-STD-020D reflow, with peak temperature up to 260 °C. Recommended profile includes ramp rate ≤3 °C/s, preheat 150–200 °C for 60–120 s, soak 217 °C for 60–150 s, and time above liquidus (217–220 °C) of 40–80 s - matching standard Pb-free SAC305 solder processes.