Overview
The NCP1256ASN65T1G, produced by onsemi, is a low-power offline PWM current mode controller designed for building cost-effective switch-mode power supplies. This component is housed in a compact TSOP-6 package and can be supplied up to 30 V. It operates at a fixed frequency of 65 kHz and features a peak current mode control with internal slope compensation. The NCP1256ASN65T1G includes several protection features such as timer-based auto-recovery short circuit protection, lossless Over Power Protection (OPP), and an easily adjustable Brown Out (BO) level. It is particularly suited for applications requiring low part-count and cost-effectiveness, such as ac-dc adapters and auxiliary power supplies.
Key Specifications
| Symbol | Rating | Min | Max | Unit | Pin | |
|---|---|---|---|---|---|---|
| VCCON | VCC increasing level at which driving pulses are authorized | 16 | 18 | 20 | V | 5 |
| VCC(min) | VCC decreasing level at which driving pulses are stopped | 8.3 | 8.9 | 9.5 | V | 5 |
| VCCHYST | Hysteresis VccON−Vcc(min) | 8.4 | - | 9.25 | V | 5 |
| ICC1 | Start-up current | 5 | 7.5 | - | μA | 5 |
| fOSC,nom | Oscillation Frequency | 61 | 65 | 70 | kHz | - |
| Dmax | Maximum duty ratio | 77 | 80 | 83 | % | - |
| fjitter | Frequency jittering in percentage of fOSC | - | - | ±5 | % | - |
Key Features
- Fixed-frequency 65 kHz current-mode control operation
- Adjustable Over Power Protection (OPP) circuit, disabled at low line
- Adjustable Brown Out level
- Frequency foldback down to 26 kHz and skip-cycle in light load conditions
- Internally-fixed slope compensation ramp
- Internally-fixed 4 ms soft-start
- 70 ms timer-based auto-recovery short-circuit protection
- Frequency jittering in normal and frequency foldback modes
- Double hiccup auto-recovery short-circuit protection
- Pre-short ready for latched OCP option
- Latched/auto-recovery OVP protection on Vcc
- Latched inputs for improved robustness (OVP and OTP implementations)
- +500 mA/ −500 mA source/sink drive capability
- EPS 2.0 compliant and Pb-free device
Applications
- Ac-dc adapters for portable devices, computers, tablets, etc.
- Auxiliary power supplies
- Low-cost ac-dc adapters and open-frame power supplies
Q & A
- What is the operating frequency of the NCP1256ASN65T1G?
The NCP1256ASN65T1G operates at a fixed frequency of 65 kHz.
- What type of protection does the NCP1256ASN65T1G offer against short circuits?
The NCP1256ASN65T1G offers 70 ms timer-based auto-recovery short-circuit protection and double hiccup auto-recovery short-circuit protection.
- How does the frequency foldback feature work in the NCP1256ASN65T1G?
The controller reduces the switching frequency down to 26 kHz as the feedback pin voltage decreases, and enters skip-cycle mode when the feedback pin voltage drops further.
- What is the purpose of the Brown Out (BO) pin in the NCP1256ASN65T1G?
The BO pin allows for the adjustment of the Brown Out level and can latch off the controller if the voltage drops below a programmed level.
- Does the NCP1256ASN65T1G have any EMI mitigation features?
Yes, the NCP1256ASN65T1G includes frequency jittering to improve the EMI signature, especially in light load conditions.
- What is the soft-start duration of the NCP1256ASN65T1G?
The soft-start duration is internally fixed at 4 ms.
- Is the NCP1256ASN65T1G compliant with any specific standards?
Yes, it is EPS 2.0 compliant and is a Pb-free device.
- What is the maximum duty ratio of the NCP1256ASN65T1G?
The maximum duty ratio is up to 83%.
- How does the Over Power Protection (OPP) work in the NCP1256ASN65T1G?
The OPP is adjustable and can be disabled at low line conditions. It also includes a non-dissipative OPP circuit.
- What are the typical applications for the NCP1256ASN65T1G?
Typical applications include ac-dc adapters for portable devices, computers, tablets, and auxiliary power supplies.
