Key Specs
| Spec | Value | Condition | Source |
|---|---|---|---|
| Control Features | Soft Start | Digi-Key | |
| Duty Cycle | - | Digi-Key | |
| Fault Protection | Current Limiting, Over Load, Over Power, Over Temperature, Over Voltage, Short Circuit | Digi-Key | |
| Internal Switch S | No | Digi-Key | |
| Mounting Type | Surface Mount | Digi-Key | |
| Operating Temperature Range | -40°C ~ 125°C (TJ) | Digi-Key | |
| Output Isolation | Isolated | Digi-Key | |
| Package Case | 8-SOIC (0.154”, 3.90mm Width) | Digi-Key | |
| Supplier Device Package | 8-SOIC | Digi-Key | |
| Supply Voltage (Typ) | 9V ~ 28V | Digi-Key | |
| Switching Frequency (Typ) | - | Digi-Key | |
| Topology | Flyback | Digi-Key | |
| Voltage Breakdown | 700V | Digi-Key | |
| Voltage Start Up | 17 V | Digi-Key |
When To Use
Use the NCP1340B9D1R2G in isolated flyback power supply applications requiring a wide supply voltage range of 9V to 28V and a high voltage breakdown capability of 700V. It is well-suited for designs where fault protection features like current limiting, overload, overpower, over temperature, over voltage, and short circuit protection are critical. Avoid using this device in non-isolated or synchronous buck converters, where integrated switches or synchronous rectification are required; instead, choose a dedicated buck controller or integrated switch device.
When Not To Use
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High current DC-DC step-down >5A load: The internal switching current limit and package thermal constraints disqualify this part for high-current applications. Use a multi-phase buck controller instead to distribute current and reduce thermal stress.
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Battery-powered sensor with μA standby: The part’s bias current is not optimized for ultra-low quiescent current, so it will drain small batteries quickly. Use a low-IQ PFM buck to maximize battery life in always-on low-power systems.
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Non-isolated 5V rail from 12V @ 3A with tight voltage regulation: The flyback topology is overkill and less efficient, and lack of synchronous rectification reduces efficiency. Use a high-current synchronous buck with external FETs for better efficiency and thermal performance.
Application Notes
The switching node connected to the primary side of the flyback transformer is the main switching node and requires the smallest possible loop area to minimize EMI and switching losses. The device’s voltage feedback and control pins are noise-sensitive; route these traces away from high di/dt switching nodes and use proper filtering if necessary. Given the internal switch is not integrated, and the device dissipates limited heat, a heatsink is generally not required at typical operating points within the -40°C to 125°C junction temperature range. However, ensure adequate PCB copper area for thermal management in high ambient temperature or high power applications.
Gotchas
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Mistake: Connecting the device in a non-isolated topology.
Failure Mode: The device’s internal protections and control features rely on isolation; operating it without proper isolation can cause unpredictable behavior or damage.
Fix: Ensure the flyback transformer provides isolation and the design follows isolated flyback topology guidelines. -
Mistake: Operating the device below the startup voltage of 17 V.
Failure Mode: The device will fail to start switching, resulting in no output regulation or power delivery.
Fix: Design the input supply and startup circuitry to provide at least 17 V at startup.