Overview
The NCP1252BDR2G, produced by onsemi, is a high-performance current-mode PWM controller designed for forward and flyback applications, particularly in ATX power supplies and adapter markets. This controller offers a comprehensive set of features to build cost-effective and reliable ac-dc switching supplies. It includes an internally fixed timer for detecting output overload, Brown-Out protection, and a compact SOIC-8 package to save PCB space.
Key Specifications
| Characteristics | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Startup threshold at which driving pulses are authorized | VCC(on) | 9.4 | 10.6 | 14.9 | V |
| Minimum Operating voltage at which driving pulses are stopped | VCC(off) | 8.4 | 9.6 | V | |
| Hysteresis between VCC(on) and VCC(min) | VCC(HYS) | 0.9 | 1.0 | 5.0 | V |
| Current Sense Voltage Threshold | VILIM | 0.92 | 1.00 | 1.08 | V |
| Leading Edge Blanking Duration | tLEB | 160 | ns | ||
| Internal IC consumption, controller switching | ICC3 | 2.0 | 2.7 | 3.5 | mA |
| Oscillator Frequency | fOSC | 92 | 100 | 108 | kHz |
| Maximum duty-cycle – B version | DCmaxB | 76 | 80 | 84 | % |
| DRV Source resistance | RSRC | 10 | 30 | Ω | |
| DRV Sink resistance | RSINK | 6 | 19 | Ω |
Key Features
- Peak Current Mode Control: Implements peak current-mode control topology, similar to UC384X-like features, to build rugged power supplies.
- Adjustable Switching Frequency: The switching frequency can be adjusted up to 500 kHz using a resistor connected to ground.
- Frequency Jittering: Frequency jittering of ±5% of the switching frequency to soften the EMI signature.
- Latched Primary Over Current Protection: With a 10 ms fixed delay (extendable to 150 ms in E version) for detecting and protecting against overcurrent conditions.
- Delayed Operation Upon Start-up: An internal fixed timer delays the start-up to ensure safe operation.
- Adjustable Soft-start Timer: Allows for a controlled start-up process using an external capacitor.
- Brown-Out Detection: Auto-recovery Brown-Out detection to protect against low input voltages.
- Gate Drive Clamping: Prevents the gate voltage from exceeding 15 V to protect power MOSFETs.
- Low Startup-Current: Achieves low no-load standby current for energy efficiency.
Applications
The NCP1252BDR2G is specifically designed for use in ATX power supplies and the adapter market. It is suitable for building cost-effective and reliable ac-dc switching supplies. The controller's features make it an ideal choice for applications requiring high performance, reliability, and efficiency.
Q & A
- What is the primary function of the NCP1252BDR2G?
The NCP1252BDR2G is a current-mode PWM controller designed for forward and flyback applications in ATX power supplies and adapter markets.
- How is the switching frequency adjusted in the NCP1252BDR2G?
The switching frequency can be adjusted using a resistor connected to ground, allowing frequencies up to 500 kHz.
- What is the purpose of frequency jittering in the NCP1252BDR2G?
Frequency jittering softens the EMI signature by spreading out peak energy within a band ±5% from the center frequency.
- How does the NCP1252BDR2G protect against overcurrent conditions?
The controller features latched primary over current protection with a 10 ms fixed delay (extendable to 150 ms in E version).
- What is the role of the internal fixed timer in the NCP1252BDR2G?
The internal fixed timer delays the start-up to ensure safe operation and prevents immediate switching upon power-up.
- How does the Brown-Out detection work in the NCP1252BDR2G?
The controller includes auto-recovery Brown-Out detection to protect against low input voltages.
- What is the maximum VCC voltage the NCP1252BDR2G can handle?
The controller can operate continuously up to 28 V and accept transient voltages up to 30 V for 10 ms.
- How does the gate drive clamping feature work?
The gate drive clamping prevents the gate voltage from exceeding 15 V to protect power MOSFETs.
- What is the typical startup current of the NCP1252BDR2G?
The startup current is low, reaching a no-load standby current for energy efficiency.
- What package type is the NCP1252BDR2G available in?
The controller is available in a compact SOIC-8 package.
