"Why did our TWS earbuds charging case 'smoke' or even suffer main chip breakdown after being charged with a certain brand of fast charger?"

"With the unified trend of the Type-C interface, and faced with non-standard charging cables and various 'modified' fast charging protocols, how can our smartwatch ensure that its sensitive Battery Management System (BMS) isn't killed by surge voltages?"

These are the most frequent complaints I hear when communicating with various consumer electronics ODM/OEM manufacturers.

Market data shows that in 2025, the global failure rate of portable devices caused by power anomalies increased by 18% year-on-year, with micro-devices such as TWS earbuds and smartwatches accounting for over 60% of these failures. More critically, consumer sensitivity to "charging safety" has now surpassed "battery life" as the primary factor in purchasing decisions. How can we build a "power firewall" for devices while keeping costs under control? The answer lies in Overvoltage Protection (OVP) and Overcurrent Protection (OCP) technologies.

I. Technological Breakthrough: How OVP/OCP Have Become a "Survival Necessity" for Portable Devices

OVP and OCP are not new technologies, but in the field of portable devices, their application is undergoing a transition from "optional" to "mandatory." The core contradiction is that the thinner and lighter the device, the smaller the "tolerance margin" for its power management IC.

u Overvoltage Protection (OVP): Countering the "High-Voltage Assassin"

When the input voltage exceeds the threshold (e.g., 6.1V), the OVP chip must turn off its internal MOSFET within nanoseconds to block high-voltage conduction. Taking Leiditech's LMOVP3608 as an example, its 100ns response speed can withstand 42V hot-plug surges — equivalent to cutting off the path before the "high-voltage lightning" strikes the device.

u Overcurrent Protection (OCP): Stopping the "Current Flood"

When a device shorts or a load becomes abnormal, the current can instantly surge to several amperes. OCP monitors the current and applies a delay (e.g., 460μs to prevent false triggering) to avoid being tripped by glitch currents, while simultaneously preventing continuous high current from burning the circuit. The LMOVP3616 features 100mA–2.0A adjustable overcurrent protection and a 460ms recovery delay, striking a balance between "protection" and "stability."

u Over-Temperature Protection (OTP): The Last Line of Defense

When the chip's junction temperature exceeds 165°C, OTP automatically turns off the power transistor and resumes operation only after it cools down to 130°C. This mechanism is particularly important in the sealed charging case of TWS earbuds, as it prevents thermal runaway caused by poor heat dissipation.

II.Precise Matching of Market Pain Points and Technical Solutions

The portable device market is currently showing three major trends, and OVP/OCP technology precisely targets these pain points:

u Miniaturization and high integration density

The BCV3608 in SOT23 package measures only 2.9mm × 2.3mm and is compatible with standard SMT production lines, requiring no specialized DFN equipment. For devices like TWS earbuds, where "every square millimeter counts," package size directly determines the feasibility of PCB layout.

u Widespread adoption of fast charging and associated power risks

With the penetration rate of PD and QC fast charging protocols exceeding 70%, the input voltage fluctuation range has expanded. The LMOVP3608 features a 50V withstand voltage and a 10ms power-on soft-start time, making it compatible with various fast chargers and avoiding high-voltage shocks caused by protocol handshake failures.

u Cost sensitivity and mass production efficiency

The LMOVP3608 requires no input or output capacitors, saving approximately ¥0.02 in BOM cost per unit. For a TWS earbud manufacturer shipping tens of millions of units annually, this translates to hundreds of thousands of yuan in cost optimization per year.

III.The LMOVP3608 requires no input or output capacitors, saving approximately ¥0.02 in BOM cost per unit. For a TWS earbud manufacturer shipping tens of millions of units annually, this translates to hundreds of thousands of yuan in cost optimization per year.

To address the different needs of portable devices, Shanghai Leiditech has launched two star products:

LMOVP3608: The cost-effective choice

With its "40V hot-plug capability" and "no capacitor required" features, it has become the "standard" chip in the TWS earbuds market.

LMOVP3616: High-reliability upgrade

It is suitable for tablets and navigation devices that have strict requirements for power supply stability. Its SOT23-6L package supports additional functional pins, such as the chip enable (CE) output and the FAULT operating status output to the MCU.

IV.Typical Application Circuit: From Theory to Practice

To help engineers better understand the application of these two chips, the following are their typical circuit designs:

1、LMOVP3608 Typical Application Circuit (Minimalist Design)

The design philosophy of the LMOVP3608 is "simplicity." Its typical circuit requires only the chip itself and decoupling capacitors at the input and output (which can even be omitted), making it highly suitable for space-constrained TWS earbud charging cases.

Circuit connection:

Input (VIN): Connect to the VBUS of the Type-C port. It is recommended to place a TVS diode at the input first, based on the input voltage, to prevent input voltage surges exceeding 50V from damaging the LMOVP3608. Then, place a 0.1μF/50V capacitor (optional, for filtering purposes) in parallel.

Output (VOUT): Connect to the downstream charging IC or battery protection board. It is recommended to place a 0.1μF capacitor (optional) in parallel.

Ground (GND): Connect directly to ground.

Advantage: The entire circuit requires only three pins, occupies very little PCB area, and needs no additional external components, significantly reducing BOM cost.

2.LMOVP3608 Typical Application Circuit (Minimalist Design)

The LMOVP3616 adds "Chip Enable (CE)" and "Fault Indicator (FAULT)" functions on top of the LMOVP3608, making it suitable for smart devices that require interaction with a host MCU.

Circuit connection:

Input/Output: Same as the LMOVP3608 — connect a 0.1μF capacitor to each of the VIN and VOUT pins to ensure 42V hot-plug capability.

It is recommended to place a TVS diode at the input first, based on the input voltage, to prevent input voltage surges exceeding 50V from damaging the LMOVP3616.

Enable pin (CE /): Connect it to an MCU GPIO through a 10kΩ resistor. When CE is low, the chip turns on and operates normally.

Fault indicator (FAULT): Open-drain output, requiring an external 10kΩ pull-up resistor to VCC. When overvoltage or overcurrent occurs, the FAULT pin is pulled low, allowing the MCU to read this signal and trigger an alarm (such as an LED flashing or an on-screen message).

Overcurrent setting (ILIM): Adjust the overcurrent threshold using an external resistor (RILIM). The formula is: I_OCP = 1540 / (R_ILIM + 752).Advantage: Supports MCU active control and fault feedback, enhancing system intelligence. Suitable for high-end devices such as tablets and navigation instruments.

V.Conclusion: From "Passive Protection" to "Active Safety"

The value of OVP/OCP technology has long surpassed the realm of "fault remediation." In the portable device market, it serves both as a "shield" against poor-quality chargers and as a "key" to achieving high-integration designs. With the proliferation of chips such as the LMOVP3608 and LMOVP3616, we are witnessing a trend: safety protection is no longer a cost burden, but rather a core component of product competitiveness.

In the future, as AIoT devices impose higher demands on power management, OVP/OCP technologies may integrate with intelligent diagnostics, adaptive protection, and other functions, becoming a key part of the "active safety" ecosystem for portable devices. Shanghai Leiditech's continuous innovation is undoubtedly injecting strong momentum into this process.