**High cost-performance stereo solution: Dual ChipSourceTek-CST8337 achieves a 2×10W boost design**

**February 11, 2022**

**Abstract**

    Just like two musicians in perfect harmony playing a symphony, the two ChipSourceTek-CST8337 chips work in exquisite collaboration to drive the dual-channel output with a single boost circuit. One of them transforms into an "energy hub", directly feeding its boosted HPVDD to the other, eliminating redundant peripheral circuits and building a 2×10W stereo stage on the extremely precious PCB. This design not only maintains the purity of sound quality but also opens up a new path for cost-sensitive applications.

**Highlights of the plan**

1. **Exquisite packaging and elegant layout**

    The ChipSourceTek-CST8337 adopts the ESSOP-10 compact package. The dual chips stand side by side like a pair of miniature books, requiring only a PCB space the size of a coin, leaving ample room for a compact design.

2. **Streamline the periphery and optimize costs**

    The traditional solution requires two sets of boost devices, while this design only needs one set of inductors and Schottky diodes. Just like the ingenious operation mode of shared bikes, it significantly reduces the BOM cost and layout complexity.

3. **The mode is dynamic and the sound quality is guaranteed**

    The AB/D class switchable function fills the market gap. Users can not only enjoy the high efficiency of D class but also choose the mellow sound of AB class. When switching, it is necessary to pay attention to the 100ms "silent period" of the enable signal, which is like a deep breath of the audio system.

4. **Powerful performance, instant peace of mind**

    The 8A instantaneous input current reserve is like a sprinting athlete ready to go, ensuring that the dual channels can output at full capacity with ease and eliminating the compromise on sound quality caused by power bottlenecks.

5. **Independent channels, pure reproduction**

    The left and right channels are separated to form an "acoustic isolation wall", with a crosstalk suppression ratio better than -70dB and THD+N as low as 0.03%, making every note as transparent as crystal.

**Detailed explanation of application circuits**

The circuit shown in Figure 2 is like a precise gear set. Two ChipSourceTek-CST8337 chips work together through the following key meshing points:

- ** Control Center ** : Connect the VCTRL (Pin3) of the two chips in parallel to form a unified "baton", simultaneously managing the AB/D mode switch (note that a "rest" of ≥100ms should be given during the switch).

- ** Energy Artery ** : The boost circuit of chip #1 serves as the "heart", and its HPVDD output is directly connected to chip #2 Pin9, eliminating the need for repetitive boost modules.

- ** Simplification Rule ** : Keep the PIN 6/7/8 of chip #2 in a "suspended state", just like unused spare strings.

- ** Safety Threshold ** : The upper limit of the current is set through the Rlim resistor #1 (recommended ≤43kΩ), and the matching capacitor is ≥1μF to smooth out the start-up impact and prevent the system from "overload panting".

**Electrical characteristics**

Test conditions: AV=26dB, TA=25℃, VBAT=3.7V*

- Peak efficiency: 92% (Class D mode)

- Static current: < 2mA (standby state)

- Frequency response range: 20Hz-20kHz (±0.5dB)

- Signal-to-noise ratio: ≥95dB (A-weighted)