Overview
The NCP1252CDR2G, produced by onsemi, is a high-performance current-mode PWM controller designed for building cost-effective and reliable AC-DC switching supplies, particularly for ATX power supplies and the adapter market. This controller integrates several key features to ensure robust and efficient power supply operation.
Key Specifications
| Characteristics | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Startup threshold at which driving pulses are authorized (VCC increasing) | VCC(on) | 9.4 | 13.1 | 10.6 | V |
| Minimum Operating voltage at which driving pulses are stopped (VCC decreasing) | VCC(off) | 8.4 | 9 | 9.6 | V |
| Hysteresis between VCC(on) and VCC(min) | VCC(HYS) | 0.9 | 4.5 | 1.0 | V |
| Current Sense Voltage Threshold | VILIM | 0.92 | 1 | 1.08 | V |
| Leading Edge Blanking Duration | tLEB | - | 160 | - | ns |
| Oscillator Frequency (RT = 43 kΩ & DRV pin = 47 kΩ) | fOSC | 92 | 100 | 108 | kHz |
| Maximum operating frequency | fMAX | - | - | 500 | kHz |
| Maximum duty-cycle (C version) | DCmaxC | 61 | 65 | 69 | % |
| 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 precisely set between 50 kHz and 500 kHz using a resistor connected to ground.
- Frequency Jittering: The controller includes frequency jittering to soften the EMI signature by spreading out peak energy within a band ±5% from the center frequency.
- Brown-Out Detection: Auto-recovery Brown-Out detection protects against low input voltages and improves converter safety.
- Delayed Operation Upon Start-up: An internal fixed timer delays operation upon start-up to ensure stable startup conditions.
- Adjustable Soft-Start Timer: A capacitor connected to the soft-start pin selects the soft-start duration, ensuring a gradual increase in output power.
- Latched Primary Over Current Protection: Provides protection against overcurrent conditions with a fixed delay of 10 ms (extendable to 150 ms in E version).
- Gate Drive Clamping: Prevents the gate voltage from exceeding 15 V, compatible with many power MOSFETs.
- Low Startup-Current: Achieves low no-load standby current, enhancing efficiency in standby modes.
Applications
The NCP1252CDR2G 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, efficiency, and reliability.
Q & A
- What is the primary function of the NCP1252CDR2G controller?
The NCP1252CDR2G is a current-mode PWM controller designed to build cost-effective and reliable AC-DC switching supplies, particularly for ATX power supplies and the adapter market.
- What is the adjustable switching frequency range of the NCP1252CDR2G?
The switching frequency can be adjusted between 50 kHz and 500 kHz using a resistor connected to ground.
- How does the NCP1252CDR2G protect against low input voltages?
The controller features auto-recovery Brown-Out detection to protect against low input voltages and improve converter safety.
- What is the purpose of the internal fixed timer in the NCP1252CDR2G?
The internal fixed timer delays operation upon start-up to ensure stable startup conditions.
- How is the soft-start duration adjusted in the NCP1252CDR2G?
The soft-start duration is adjusted using a capacitor connected to the soft-start pin.
- What type of overcurrent protection does the NCP1252CDR2G offer?
The controller provides latched primary overcurrent protection with a fixed delay of 10 ms (extendable to 150 ms in E version).
- Why is gate drive clamping important in the NCP1252CDR2G?
Gate drive clamping prevents the gate voltage from exceeding 15 V, which is compatible with many power MOSFETs and prevents damage.
- What is the maximum operating frequency of the NCP1252CDR2G?
The maximum operating frequency is 500 kHz.
- How does the NCP1252CDR2G reduce EMI?
The controller includes frequency jittering to soften the EMI signature by spreading out peak energy within a band ±5% from the center frequency.
- What is the typical supply voltage range for the NCP1252CDR2G?
The controller operates with a supply voltage range from 8 V to 28 V and can accept transient voltages up to 30 V for 10 ms.
