In recent years, the demand for storage and data transmission brought about by new business forms such as cloud computing and remote services has been constantly rising. SDRAM As an upgrade of DRAM, it is moving towards a higher external data transmission rate, a more advanced address / command and control bus topology architecture.
In order to ensure SDRAM transmission rate, stable and efficient power supply is an essential link. In today's product development, power chips have more and more strict requirements: higher stability, lower power consumption, smaller space requirements, at least 2 power supply for power supply.
Take DDR 4 as an example, it requires 3 power supply: VDDQ(1.2V) the required current is large, VTT(0.6V) and VPP(2.5V) the required current is small. Traditional power supply scheme usually uses one BUCK line and two LDO lines to supply power. However, but this power supply scheme has obvious disadvantages: it occupies large space and requires many chips and peripheral devices.
DDR power supply integrated power supply solution
In response to this market demand, Chang Microelectronics independently developed and launched a full switch mode converter with IS6630A / C / D —— up to 10A, which contains fixed LDO output and can support fully integrated DDR power supply scheme. The power supply solution highly integrates the requirements of DDR three-way power supply into a 3mm * 3mm * 0.85mm QFN package chip, realizing an integrated power supply solution for DDR power supply with very little space.
Take IS6630A as an example, due to the simultaneous integration of BUCK (VDDQ), two LDO (VTT, VPP) and buffer low noise reference output (VTTREF) power channel, it can provide an integrated power supply solution for DDR 4 / DDR / 3 / DDR3L, that is, only one IS6630A can meet the 3 power supply of DDR 4 and 2 power supply required by DDR 3 / DDR3L. At the same time, the output end of these three power supply only needs a small amount of ceramic capacitor as the output capacitor, which further saves the space on the PCB board and the required devices, and achieves the ultra-compact circuit board design.
IS6630A Only provide VIN, VPPIN, VCC three-way power supply and enabling signals EN1, EN2 can work normally. The BUCK converter VDDQ can provide a continuous current of up to 10A in the VIN of 4.5 V to 22 V and the output voltage VDDQ of 0.6V~3.3V, Very high power density; The VPPIN is the input voltage of the VPP LDO, Input the support for 2.6V~3.3V, The output is fixed to 2.5V, The LDO output terminal needs only a 22 uF ceramic capacitor to provide a continuous current of 1A; While the input voltage of VTT LDO is the output VDDQ of the BUCK converter, VTTREF (Buffered low-noise reference output) accurately tracks VDDQ / 2 values for VTT, Fix the output voltage to VDDQ / 2, The output end also needs only a ceramic capacitor of 22 uF to absorb or provide a continuous current of 1A.
Typical Application circuit diagram of Figure 4 IS6630A
Figure 5 IS6630A / C / D Specific application classification and required voltmeter
Fast-state transient response and high-precision voltage
IS6630A / C / D successfully achieves the three-way output voltage with the ultra-small volume and has excellent performance. Its BUCK converter adopts the long industrial micro patent TCOTTMControl mode, with only a wide input voltage range, excellent load and linear adjustment rate make the output voltage accuracy reach ± 1% under different load current and input voltage;
Figure 6 Schematic representation of the transient regulation in IS6630A / C /
FIG. 7 Load adjustment curve of IS6630A/C/D
Figure 8 Linelinear plot of IS6630A / C / D
High efficiency, low power consumption
Thanks to the low conduction resistance of the MOS tube and the technical optimization of the drive circuit, the IS6630A / C / D can be up to 92% efficient under VIN=12V,VOUT=1.2V conditions. Under the condition of light load, the chip is fixed to the DCM mode, that is, the intermittent conduction mode, which further reduces the power consumption of the chip and improves the overall working efficiency of the chip. However, in the DCM mode, the chip switch frequency is within the auditory range of the human ear, and the audible noise is generated when the energy is high. For this situation, this series of chips adopts USM mode based on DCM mode, namely ultrasonic mode.Compared with DCM mode, when the chip works in this mode, the lower tube can be opened one more time in a cycle, increasing the switching frequency to make it beyond the auditory range of the human ear, and the efficiency will not be significantly reduced.
Figure 9. Schematic representation of the efficiency curves for IS6630A / C / D
As a fully integrated DDR power supply integrated power supply solution, IS6630A / C / D is mainly used in high data transmission rate / wide output voltage range of pen, data center and other industries, taking into account high efficiency, high performance, while having a smaller application volume, can match the mainstream market demand, and actively enable the development of DDR industry.
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