Overview
The NCP4305, produced by onsemi, is a high-performance secondary side synchronous rectification driver designed for use in switch mode power supplies (SMPS). This driver is tailored to control synchronous rectification MOSFETs in various topologies, including discontinuous conduction mode (DCM) or continuous conduction mode (CCM) flyback, quasi-resonant flyback, forward, and half-bridge resonant LLC converters. The NCP4305 ensures reliable and noiseless operation of the synchronous rectification system through its Self Synchronization feature and the use of Kelvin connection to the MOSFET for high efficiency at full load. It also incorporates a light load detection architecture to maintain high efficiency during light load conditions.
Key Specifications
| Parameter | Symbol | Unit | Min | Typ | Max |
|---|---|---|---|---|---|
| Supply Voltage | VCC | V | -0.3 | - | 37.0 |
| Driver Output Voltage | VDRV | V | -0.3 | - | 17.0 |
| Minimum Driver Output Voltage | VDRVLLDMIN | V | 0.0 | 0.4 | 1.2 |
| Total Propagation Delay From CS to DRV Output On | tPD_ON | ns | 35 | 60 | - |
| Total Propagation Delay From CS to DRV Output Off | tPD_OFF | ns | 12 | 23 | - |
| Turn On CS Threshold Voltage | VTH_CS_ON | mV | -120 | -75 | -40 |
| Turn Off CS Threshold Voltage | VTH_CS_OFF | mV | -1 | 0 | - |
| Trigger Threshold Voltage | VTRIG_TH | V | 1.87 | 2.02 | 2.18 |
Key Features
- High Performance Drivers: The NCP4305 features high-performance drivers with high sink current capability, ensuring minimal turn-off time and maximizing efficiency.
- Self Synchronization: This feature ensures reliable and noiseless operation of the synchronous rectification system.
- Kelvin Connection: The driver uses a Kelvin connection to the MOSFET, enhancing efficiency at full load.
- Light Load Detection: The IC includes a light load detection architecture to maintain high efficiency during light load conditions.
- Adjustable Minimum On-Time and Off-Time Blanking Periods: These periods can be adjusted independently using external resistors to prevent false triggering due to PCB layout and parasitic elements.
- Ultrafast Trigger Input: This input allows for further efficiency improvements in CCM applications and can also disable the IC to activate a low consumption standby mode.
- MAX_TON Circuit (in some versions): Helps quasi-resonant controllers to operate in CCM mode under heavy loads.
- LLD Pin for Load Dependent Gate Driver Voltage Clamp: Reduces issues during transitions from disabled to full driver output voltage and can activate a disable state to decrease power consumption in no-load conditions.
Applications
The NCP4305 is versatile and can be used in various switch mode power supply topologies, including:
- DCM or CCM flyback converters
- Quasi-resonant flyback converters
- Forward converters
- Half-bridge resonant LLC converters
It is particularly suitable for applications such as notebook adapters, cell phone chargers, and LCD TV adapters, where high efficiency and reliability are crucial.
Q & A
- What is the primary function of the NCP4305?
The NCP4305 is a high-performance driver designed to control synchronous rectification MOSFETs in switch mode power supplies.
- What are the key benefits of using the NCP4305?
The key benefits include high efficiency, reliable and noiseless operation, adjustable minimum on-time and off-time blanking periods, and ultrafast trigger input for improved efficiency.
- What is the supply voltage range for the NCP4305?
The supply voltage range is from 4 V (for A, D, and Q options) or 8 V (for B and C options) to 37 V.
- How does the NCP4305 handle light load conditions?
The NCP4305 includes a light load detection architecture to maintain high efficiency during light load conditions.
- What is the purpose of the LLD pin?
The LLD pin can be used to reduce gate driver voltage clamp according to application load conditions and to activate a disable state to decrease power consumption in no-load conditions.
- Can the NCP4305 be used in CCM applications?
Yes, the NCP4305 can be used in CCM applications, and it includes features such as an ultrafast trigger input to improve efficiency in these modes.
- How does the NCP4305 prevent false triggering?
The NCP4305 prevents false triggering through adjustable minimum on-time and off-time blanking periods, which can be set using external resistors.
- What is the MAX_TON circuit used for?
The MAX_TON circuit, available in some versions, helps quasi-resonant controllers to operate in CCM mode under heavy loads.
- How does the NCP4305 ensure efficient operation at full load?
The NCP4305 ensures efficient operation at full load through the use of a Kelvin connection to the MOSFET and its high sink current capability.
- Can the NCP4305 be used as a standalone IC or with a primary side controller?
The NCP4305 can be used either as a standalone IC or as a companion IC to a primary side controller to achieve efficient synchronous rectification.
