Charge pump converter, no inductor, small size
Inductive boost converter, low ripple
High competitiveness in high-power applications

SSD storage is widely used in PCs, data centers, and telecommunications applications. SSDs have the advantage of being faster and smaller than HDDs. SSDs with the new PCIe NVMe host controller interface specification are three times faster in write speeds and six times faster in read speeds than existing SATA (Serial Advanced Technology Attachment) SSDs.

However, SSDs face the critical challenge of increasing NAND (Not-AND) flash write and erase speeds and solving heat dissipation issues. As shown in Figure 1, a power supply is required to support the write/erase of NAND chips.
You can calculate the current during writing/erasing using the formula below.
For example, if C is 100pF and R is 1M, and write/erase is completed in 100ns, this current is about 12mA. Applications such as enterprise storage require higher current because they require higher capacitance (increase in C) and faster speed (decrease in t).

Write/erase speeds depend on power supply and heat dissipation capabilities. If power performance fails to provide the necessary current due to current capacity limitations, write/erase speeds will drop, affecting the storage system's response time.


Charge Pump Converter vs. Inductive Boost Converter
There are two types of step-up converters: charge pump converters and inductive boost converters. Since charge pump converters do not use inductors, the solution size is relatively smaller, and they can be placed inside a NAND cell as shown in Figure 2.
Charge pump solutions for applications requiring high output power necessitate higher capacitance for charging and discharging under high loads. Additionally, efficiency at high loads is relatively low due to power loss in the charge/discharge capacitors. Output ripple and noise remain high even under high load conditions.

Due to low current capacity limits, charge pump converters are suitable for relatively low-power applications. Since it does not use an inductor, the design is easy and the solution size is small, so the efficiency is moderate.

On the other hand, inductive boost converters can provide higher current than charge pump converters and are a more competitive solution for high-power applications because they have low ripple. Since the inductor current can supply the load current, the output voltage of the boost converter is flatter across the entire load range. As shown in Figure 3, a single boost converter outside the NAND chip can power multiple chips.
The TPS61372 synchronous boost converter is a suitable solution for supplying the power required for SSD NAND chip writing and erasing, featuring reduced size and minimized external components. Compared to conventional charge pump converters, the TPS61372 is capable of providing high-quality power for NAND chip writing and erasing.

This article is a summary of a piece by Yangwei Yu, an engineer at Texas Instruments.