December 16, 2009

Sanken Launches NR880K Series: Buck Switching Regulator ICs
Achieving Higher Efficiency (94%) and
Reducing the Number of External Components by Built-in Phase Compensation Circuit

Sanken Electric Co., Ltd. has developed the NR880K series of synchronous rectification type, buck switching regulator ICs; Output Current: 3A, Output Voltage: (Variable) 0.8 - 14V, (Fixed) 3.3V, 5.0V, and just started the sample shipment. The sample price is ¥200 per unit. The mass production shipment is scheduled to start with 1,000,000 units per month in coming April and ramp up to 5,000,000 units per month in the spring of 2011.
1. Development Background and Product Overview
  In AV equipment such as flat panel TVs and OA equipment such as printers, many DSPs and other signal processing ICs are used.

For the regulator IC that supplies the power source to those ICs, the input power is supplied from the main power supply, conventionally incorporating multiple output circuits, such as 5V system, 9V system and 12V system. However, in accordance with the recent lower price trend of equipment, the number of output circuits of main power supply is reduced and only one output circuit supplies the power, for cost down. As a result, the input voltage to regulator IC becomes higher like 12V.

On the other hand, in accordance with the recent lower power supply voltage trend of signal processing ICs, the output voltage of regulator IC becomes lower. Therefore, the regulator IC efficiency gets lower as the difference of input / output voltage is higher.

Considering the above, Sanken has developed the NR880K series of buck switching regulator ICs with the enhanced efficiency of 94% (Sanken conventional products: 92%), by lowering ON resistance of output side MOSFET, among two built-in MOSFETs.

Additionally, the problem that the efficiency decreases under low load conditions, such as standby, has been improved to 33% (at VIN = 18V, VO = 3.3V, IO = 0.02A) (Sanken conventional products: 22%), by devising the internal circuit of regulator IC.

Because of the higher performance of recent signal processing ICs, the power consumption may increase rapidly depending on processing amount. At that time, the output voltage of regulator IC drops momentarily. And the malfunctions of signal processing ICs may be caused, if the power supply voltage drops significantly. For the NR880K series, the above malfunctions are prevented, because the momentary output voltage drop is recovered with high speed by adopting the current mode control method (*).

Furthermore, as the highest-level fine process (0.35µm) among the analog IC manufacturing processes is used for the NR880K series, the chip size is reduced. By this small sizing and the enhanced circuit design accuracy, two components for phase compensation are built-in. As a result, the number of external components and the design works are reduced. For the conventional products with built-in phase compensation circuit, the input / output conditions may be limited. For the NR880K series, the input / output conditions have no limitation, by utilizing Sanken original circuit.

* Current Mode Control Method
The method is one of the control methods that make the output voltage stable. The voltage mode control stabilizes the output voltage by the feedback only of output voltage to IC. The current mode control stabilizes the output voltage by the feedbacks of both output voltage and output current to IC. In the voltage mode control, the switching operation is unstable and abnormal oscillations may easily occur.
On the other hand, in the current mode control, the switching operation is more stable, abnormal oscillations do not occur easily, and the regulation characteristics are excellent.
Because of the current mode control advantages, a small size ceramic capacitor with low resistance is applicable for the output-smoothing capacitor, which suppresses abnormal oscillations. An output-smoothing coil with low capacity is also applicable.
2. Features
·High Efficiency : 94% Max (at VIN = 8V, VO = 5V, IO = 0.8A)
·Current Mode Control Method : Ceramic capacitor applicable for output capacitor
·Built-in Phase Compensation Circuit : No external phase compensation circuit
·Oscillation Frequency : 350kHz, 500kHz, 750kHz
·Protection Functions : Drooping type overcurrent protection function, Thermal shutdown protection function, Undervoltage lockout function
·Additional Functions : Built-in output ON / OFF control function Built-in soft-start function with adjustable time
·Small Package : SOP 8-pin package with exposed thermal pad (HSOP8) (Mold portion: 5.2 × 4.4 × 1.5mm)
3. Applications
  AV Equipment: Flat Panel TVs, Blu-ray Recorders / Players, Others
OA Equipment: Printers, Others
Power Supplies for DSPs, Other Signal Processing ICs
4.  Specifications
Parameter Rating Unit
NR880K NR883K NR884K NR881K NR882K
Input Voltage Range 4.5 - 20 6.3 - 20 8 - 20 V
Output Current 3 A
Reference Voltage (Typ) 0.8 - - V
Output Voltage 0.8 - 14 3.3 5.0 V
Operating Frequency (Typ) 350 500 750 350 350 kHz
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