ISM6636x As one of the most compact 6A DC step-down power modules in the industry, its tiny IC package volume not only provides a more flexible design space for power supply design, but also shows a high degree of simplicity in peripheral applications. In addition to the necessary enabling, input and output filter capacitors and feedback lines, ISM6636x allows engineers to add or subtract other peripheral devices according to the actual needs, meeting the needs of engineers for the overall performance optimization of the system.

ISM6636x The minimalist design greatly saves engineers' design time. The design concept is designed to minimize the footprint of the power system while maintaining excellent performance levels. As a technology-leading power module, ISM6636x meets the requirements of maximum carrier 6A current design, and also provides efficient, flexible and customizable solutions for various application scenarios. For the design features of ISM6636x, three recommendations will be made to further optimize the module performance:

1. Input and output capacitance placement requirements

 ISM6636x As a BUCK power module, the control of the MOS switch is the key to realize the BUCK function, but in the process of the MOS switch, the switch noise is difficult to avoid. Especially under the influence of high-frequency fast-switching MOS, there is a parasitic impedance in the wiring, which will affect the performance of the chip. If the distance between the IC pin and the bypass capacitor is too long, the bypass capacitor filter may be poor, which will affect the performance of the chip. To effectively reduce the switch noise, it is usually necessary to place the bypass capacitor as close to the IC as possible.

 When selecting the bypass capacitor of the proximal IC, the small capacity and small package capacitor with good high frequency performance are often used to filter the high frequency band capacitor. Generally, the patch capacitor of 100 nF ~ 1 uF is used to achieve the high frequency filter. Given that low-band noise has a longer wavelength and large capacity capacitance usually has more excellent low-band filtering performance, large capacity capacitance is generally placed behind the small high-frequency capacitance near the chip.

Similarly, to maximize high-frequency interference, the VIN and VCC capacitors also need to be placed in the same layer as the chip and as close to the chip as possible. Such layout considerations are designed to effectively respond to high-frequency noise and ensure the stability and superior performance of the power module.

2. The overhole should be placed near the power pin

As shown, holes were placed proximal to VIN / VOUT / GND and the number of holes was increased as much as possible on the copper foil directly below PIN 16. These outs have the following professional uses:

（1） Increasing the number of proximal overholes is conducive to IC heat dissipation:

ISM6636x As A 6A POL module, its power pin carries a large current. If the number of proximal overholes is insufficient and the distribution of copper overlying current density is uneven, the current load of a single overhole will be significantly increased, resulting in the temperature rise of the chip, and thus affecting the overall performance of the chip. By increasing the number of proximal perforations, we can effectively balance the current density distribution, improve the heat dissipation effect of the chip, and ensure the stable operation of the chip in the condition of high current.

（2） To reduce the loss:

When the IC is at a high temperature environment, its performance will be affected to a certain extent, and the internal loss will also increase accordingly. In order to achieve better performance, increasing the number of holes in the proximend of the chip becomes a key strategy, which can more effectively reduce the loss inside the chip. By improving the heat dissipation effect and effectively reducing the working temperature, the chip performance level of the chip is maintained to the maximum extent to ensure that it can achieve superior electrical characteristics under various working conditions.

3. Feedback pin suggestions

ISM6636x In the feedback pin design supports two kinds of partial voltage discharge: one is to directly connect the feedback pin VOS to the output VOUT, and the other is to connect the output VOUT through the partial voltage resistance.

（1） Feedback pin VOS direct connection output VOUT:

In this design, the VOS is directly connected to the VOUT via a 0R resistor. To ensure the reliability of signal transmission, it is recommended to walk as short as possible and keep the line width within the range of 8 ~ 10 mil. This helps to reduce the impedance mismatch during transmission and improve the signal integrity.

(2) Connect to the output VOUT through the divider resistor:

In this design, the VOS and VOUT divider resistors are placed close to the IC. In order to optimize the stability of signal transmission, it is recommended to use the wiring method as shown in the following figure, that is, to sample the voltage through the differential line to both ends of the output capacitor. In this case, the line width selection range should be maintained at 8 to 10mil to ensure that low signal distortion and minimal transmission loss are maintained during transmission.

These two feedback pin routing layouts are designed to minimize circuit noise and impedance mismatch in signal transmission, thus ensuring the full performance of the ISM6636X under different partial voltage discharge modes.

【 About IVS 】

 IVS was founded in May 2016, located in Dongguan Songshan Lake, has a professional technical team, adhere to independent forward research and development, committed to high-performance low-voltage high-current power supply chip design. Aiming at the domestic gap in the XPU power supply field, we launched a full set of 6A-800A power supply solutions, breaking the status quo of foreign chip monopoly. Products include switching power supply, polyphase controller, intelligent power stage, power module, etc., can be widely used in server, computer, communication, consumer electronics and other markets.