SSM6N57NU,LF vs SSM6N815R,LF MOSFET Arrays: Technical Comparison for Hardware Engineers
Quick verdict
For low-voltage, higher-current switching applications where conduction losses and board space matter, the SSM6N57NU,LF is the better choice due to its lower R_DS(on) and smaller 6-µDFN package. For higher-voltage applications up to 100 V with moderate current requirements and slightly higher power dissipation, the SSM6N815R,LF is more suitable thanks to its 100 V rating and higher power handling capability, despite its higher on-resistance and larger package.
Spec comparison table
| Spec | SSM6N57NU,LF | SSM6N815R,LF | Notes |
|---|---|---|---|
| Configuration | 2 N-Channel (Dual) | 2 N-Channel (Dual) | Equivalent dual MOSFET arrays. |
| Continuous Drain Current (I_D) @ 25°C | 4 A | 2 A | SSM6N57NU,LF supports twice the continuous current, better for higher current loads. |
| Drain-Source Voltage (V_DS max) | 30 V | 100 V | SSM6N815R,LF supports over 3x higher voltage, necessary for high-voltage rails. |
| Gate Charge Q_g @ 4.5 V (max) | 4 nC | 3.1 nC | SSM6N815R,LF has lower gate charge, reducing gate drive losses and switching time. |
| Input Capacitance C_iss @ V_DS | 310 pF @ 10 V | 290 pF @ 15 V | Slightly lower input capacitance on SSM6N815R, marginally easier to drive at high speed. |
| Mounting Type | Surface Mount | Surface Mount | Both are surface mount. |
| Operating Temperature (T_j max) | 150°C | 150°C | Equivalent max junction temperature. |
| Package | 6-WDFN Exposed Pad (2x2 mm) | 6-TSOP-F Flat Leads | SSM6N57NU,LF is smaller (2x2 mm) with exposed pad for thermal relief; SSM6N815R,LF larger and flat leads. |
| Max Power Dissipation (P_D) | 1 W | 1.8 W (Ta) | SSM6N815R,LF can dissipate more power, better for thermally demanding applications. |
| R_DS(on) max @ I_D, V_GS | 46 mΩ @ 2 A, 4.5 V | 103 mΩ @ 2 A, 10 V | SSM6N57NU,LF offers less than half the on-resistance, significantly reducing conduction losses. |
| Technology | MOSFET (Metal Oxide) | MOSFET (Metal Oxide) | Equivalent technology. |
| Gate Threshold Voltage (V_GS(th)) | 1 V @ 1 mA | 2.5 V @ 100 µA | SSM6N57NU,LF has lower threshold voltage, better for low-voltage gate drive. |
| Fet Feature | - | Logic Level Gate, 4 V Drive | SSM6N815R,LF specifically optimized for logic level drive, easing MCU/logic interfacing. |
| Supplier Device Package | 6-µDFN (2x2) | 6-TSOP-F | Different package types, impacting PCB layout and thermal design. |
Design trade-offs
The SSM6N57NU,LF targets low-voltage, higher-current scenarios with a compact 2x2 mm 6-µDFN package featuring an exposed pad. Its 46 mΩ R_DS(on) at 2 A and 4.5 V gate drive means conduction losses are significantly lower compared to the SSM6N815R,LF, which has more than double the on-resistance (103 mΩ at 2 A and 10 V). This translates directly into higher efficiency and less heat dissipation in current-heavy loads. The exposed pad on the 6-µDFN also aids thermal management, allowing the device to maintain performance close to its 1 W power dissipation limit.
Conversely, the SSM6N815R,LF supports a much higher voltage rating (100 V) and higher maximum power dissipation (1.8 W at ambient temperature), making it more suited for intermediate-voltage applications where 30 V devices like the SSM6N57NU,LF would be at risk. The trade-off is its higher R_DS(on), which can lead to increased conduction losses and heat, especially at higher currents. The flat lead 6-TSOP-F package is larger and may complicate dense PCB layouts but can be easier to hand-solder or rework compared to the tiny 6-µDFN.
From a gate drive perspective, the SSM6N815R,LF is explicitly designed for logic-level drive (4 V), with a lower total gate charge (3.1 nC vs 4 nC) and a threshold voltage of 2.5 V, which aligns with typical MCU I/O voltages. The SSM6N57NU,LF has a lower threshold voltage (1 V), which can be beneficial for ultra-low-voltage drive circuits but may require more careful gate drive design to avoid false turn-on or leakage. Both parts maintain similar input capacitances, so switching speed differences will mainly come from gate charge and R_DS(on).
Thermally, the SSM6N815R,LF’s higher power rating and larger package mean it can handle more sustained dissipation, but its higher R_DS(on) will generate more heat at equivalent currents. The SSM6N57NU,LF’s exposed pad and smaller size make it suitable for compact designs where thermal relief vias can be used effectively, but it is limited to 30 V and 1 W maximum power dissipation.
Cost-wise, the smaller 6-µDFN package and higher current rating of the SSM6N57NU,LF may come at a premium compared to the larger, older 6-TSOP-F package of the SSM6N815R,LF, which is more traditional and possibly cheaper in high volumes. However, cost differences should be evaluated against system-level savings from reduced losses and board size.
Use-case fit
Choose SSM6N57NU,LF when…
- Your system operates at or below 30 V DC rails and demands continuous current up to 4 A per FET.
- Minimizing conduction losses is critical for efficiency and thermal management in compact power stages.
- PCB real estate is highly constrained and an ultra-small 2x2 mm footprint is required.
- You need an exposed pad package for improved thermal dissipation on a multi-layer board with thermal vias.
- Gate drive voltage is around 4.5 V or higher, and you prefer a low threshold voltage for sensitive switching.
Choose SSM6N815R,LF when…
- Your application requires blocking voltages up to 100 V, such as intermediate DC rails or automotive electronics.
- Continuous current demand does not exceed 2 A per FET and switching losses are manageable.
- You want a logic-level gate drive optimized MOSFET that can be driven directly from 4 V logic signals.
- Higher power dissipation capability (1.8 W) is needed for thermal headroom in moderately loaded circuits.
- Your PCB layout prefers a 6-TSOP-F package with flat leads, potentially easing manual assembly or rework.
Drop-in compatibility
These two devices are not pin-compatible or footprint-compatible. The SSM6N57NU,LF comes in a 6-pin 2x2 mm WDFN with exposed pad, whereas the SSM6N815R,LF uses a 6-pin TSOP-F package with flat leads, which is physically larger and has a different pin layout. Substituting one for the other requires redesigning the PCB footprint and possibly adjusting gate drive and thermal management approaches. Without explicit Toshiba cross-reference documentation, the parts should be considered non-interchangeable in hardware.
Alternatives to consider
- SSM6N60NU,LF (Toshiba): A 60 V, 6 A dual MOSFET in a small package, offering a middle ground on voltage and current ratings.
- BSS138 (Fairchild/Nexperia): Single low-voltage logic-level MOSFET, useful for low-current switching but not a dual array.
- Si2302DS (Vishay): Dual N-channel MOSFET with similar voltage and current ratings but different package options, worth evaluating for cost and availability.
This comparison targets practical trade-offs relevant to hardware engineers designing real products requiring dual MOSFET arrays, emphasizing thermal, electrical, and physical design factors.