Sn51dp Datasheet May 2026

| Pin Number | Name | Description | | :--- | :--- | :--- | | | VIN | Input voltage (unregulated DC supply). Bypass with a low-ESR capacitor close to this pin. | | 2 | SW (Output) | Switching node – connects to the inductor and catch diode. Handles high current. | | 3 | GND | Ground reference. Must be connected to the system ground plane. | | 4 | FB (Feedback) | Voltage feedback input. Connected to a resistor divider from the output to set the desired voltage. | | 5 | COMP (Compensation) | Frequency compensation pin. A capacitor and resistor network to ground stabilizes the control loop. |

When searching for the original document, prioritize service manuals and vintage datasheet archives. For new product development, consider upgrading to a current-generation IC like the LM2576 or XL4015. However, for repairing a classic audio amplifier, industrial controller, or CRT display, the SN51DP—with its straightforward pinout and forgiving design—is still a valuable component.

Introduction In the world of power electronics, finding a reliable and efficient switching regulator IC is crucial for any design. While many components come and go, certain part numbers—like the SN51DP —maintain a quiet but significant presence in power supply designs, particularly in Japanese and Asian market equipment. If you have landed on this article, you are likely searching for the SN51DP datasheet . Whether you are repairing a power supply, designing a new DC-DC converter, or cross-referencing a part, understanding the raw technical data of this IC is essential. sn51dp datasheet

Some variants may swap pins 4 and 5 or include an enable function. Always verify with a multimeter and known schematic. Absolute Maximum Ratings (From Datasheet) Exceeding these values will destroy the IC. These are non-recoverable limits.

| Parameter | Conditions | Min | Typ | Max | Unit | | :--- | :--- | :--- | :--- | :--- | :--- | | Input Voltage Range | | 8 | | 45 | V | | Quiescent Current | VFB = 0V, No switching | | 5 | 8 | mA | | Shutdown Current | VIN only | | 100 | 200 | µA | | Reference Voltage | VFB pin | 1.20 | 1.23 | 1.26 | V | | Oscillator Frequency | | 45 | 60 | 75 | kHz | | Switch Saturation Voltage | ISW = 2A | | 0.8 | 1.2 | V | | Switch Leakage Current | VSW = 45V | | | 100 | µA | | Current Limit Threshold | Duty cycle < 50% | 3.5 | 4.0 | 4.5 | A | | Thermal Shutdown Temp | | | 150 | | °C | The most common use of the SN51DP in available documentation is a 12V-to-5V or 24V-to-5V step-down converter. Below is a typical schematic based on the datasheet reference design. | Pin Number | Name | Description |

: Always cross-check the pin function, not just pin count. The SN51DP pin 5 is Compensation ; many modern parts use that pin for Shutdown . Connecting incorrectly will cause instability or failure. Frequently Asked Questions (FAQ) Q1: Is the SN51DP a MOSFET or BJT switching IC? A: According to internal block diagrams from older datasheets, the SN51DP uses a bipolar junction transistor (BJT) as the power switch, not a MOSFET. This explains its higher saturation voltage (0.8V typical) compared to modern MOSFET-based converters. Q2: Can I use the SN51DP in a boost (step-up) converter? A: The datasheet primary application is buck. While theoretically possible, no official reference design exists for boost. Use a dedicated boost controller instead. Q3: The datasheet mentions "standby current." How do I shut down the IC? A: The SN51DP does not have a dedicated enable pin. To achieve low standby power, you must remove input voltage or use a separate MOSFET switch on the VIN line. Q4: My SN51DP runs hot even at 1A – is this normal? A: Yes, due to its BJT design, efficiency is lower (70-80%). A heat sink is mandatory above 500mA. Consider a modern alternative (e.g., LM2596) for new designs. Q5: What is the difference between SN51DP and SN51DP-H? A: The "-H" suffix indicates a higher input voltage rating – typically 60V instead of 45V. All other parameters remain the same. Conclusion The SN51DP datasheet describes a rugged, medium-power switching regulator ideal for legacy power supply repairs and low-frequency buck converter designs. While modern equivalents offer better efficiency and higher frequency, the SN51DP remains relevant due to its simple external compensation, built-in thermal protection, and electrically isolated package. Handles high current

Unfortunately, official datasheets for the SN51DP can be elusive due to its age and specific manufacturing lineage (often associated with Sanken Electric Co., Ltd.). This article consolidates verified technical information, pinout configurations, electrical characteristics, typical application circuits, and practical tips for sourcing or substituting this component.