Overview
When many products still advertise "30+ hours" as long battery life, SoundPeats released the Capsule3 Pro TWS earbuds claiming a runtime of 52 hours. A teardown revealed the Capsule3 Pro uses the HERO ChargeTM solution from MicroSource, pairing the LP7810 in the charging case with LP4080 inside the earbuds.
01 TWS Earbud Runtime Comparison
The Capsule3 Pro charging case battery is 500 mAh / 1.85 Wh, and each earbud battery is 35 mAh (0.135 Wh at 3.85 V). The case management IC is the LP7810 and the earbud charger is the LP4080. From several teardown reports, many TWS products with case batteries around 500 mAh show much shorter runtimes than the Capsule3 Pro. The HERO ChargeTM scheme used here is a key factor in the extended runtime.
02 The HERO ChargeTM Concept Behind 52 Hours
Below is a simplified system diagram for a TWS charging system. The charging case provides power to the left and right earbud charging circuits. Many Bluetooth SoCs include a linear charging circuit, though some SoCs lack it and require an external charger. When charging an earbud, the case usually supplies about 5 V to the earbud charger, and the earbud battery is charged from a lower voltage (for example 2.8 V) up to 4.2 V. The power lost equals the voltage difference between the case input and the battery multiplied by the charging current, and this loss is dissipated as heat. If the average battery voltage in the constant-current (CC) phase is 3.7 V, the efficiency is roughly 74% (= 3.7 / 5). Additional losses in the case circuitry further reduce overall power transfer efficiency from case battery to earbud battery.
Because the voltage difference at the earbud charger is the main source of loss, reducing that difference raises efficiency and reduces heat. The right-hand diagram shows a "low-voltage-difference" or "voltage-following" charging approach. To follow the earbud battery voltage, the case must know the earbud battery voltage in real time so it can output a voltage slightly higher than that value. But the case and earbud are connected only by power and ground, with no dedicated feedback line to provide the battery voltage. Two practical methods are used today:
- Case and earbud communicate; the case periodically queries the earbud MCU for battery voltage and then adds a margin of around 300 mV.
- In the CC phase, the case monitors whether earbud charging current drops; a drop indicates the internal voltage headroom is too low, so the case raises its output voltage. This requires adding a current-sense resistor and a high-precision ADC to measure current, creating a trade-off between added loss from a larger resistor and loss of accuracy with a smaller resistor.
Both methods require software participation to achieve voltage following, increasing development complexity and cost. HERO ChargeTM implements voltage following automatically without software intervention. HERO stands for Highly Efficient, Rapid & Optimized. The case automatically outputs a voltage slightly above the earbud battery voltage. For example, with the LP7810 in the CC phase, if the CC current is set low, the voltage difference can be about 50 mV; at higher current, the charging circuit behaves like an approximately 0.5 W resistor. Figure 5 shows a measured charging trace where the LP7810+LP4080 charges a 50 mAh earbud battery at 150 mA (3C). The low voltage difference in the CC phase is around 75 mV. With an average battery voltage of 3.7 V, the linear charger efficiency approaches 98% (= 3.7 / 3.775). After accounting for boost-stage losses, case-to-earbud power transfer efficiency can exceed 90%.
Figure 6 shows measured data for an LP7811+LP4081 pair using a 540 mAh charging-case battery to charge two 50 mAh earbuds. The falling trace is the remaining capacity of the case battery; the rising traces are cumulative capacity received by each earbud. The test stopped when the case battery had 14 mAh remaining, so the case delivered 526 mAh and the two earbuds received 428 mAh, giving a transfer efficiency of 81% (= 428 / 526). For traditional linear charging, this transfer efficiency is roughly in the low 60s percent, so HERO ChargeTM can increase effective case runtime by over 20%, and in some cases up to 30%.
Key characteristics of the HERO ChargeTM scheme:
- High internal earbud charging efficiency allows fast charging with low heat even at high C-rates. For a 40 mAh earbud battery, the LP7811 supports up to 7.5C charging current, and the LP7810 supports above 6C.
- High efficiency minimizes wasted charge during each earbud charging cycle, so more energy remains in the case battery and case runtime increases significantly. This effect applies even without fast charging; Capsule3 Pro leverages this property.
- No MCU software intervention is required in the charging loop, simplifying development and debugging.
- Because charging remains linear, no large external inductors are needed and PCB area stays small.
03 HERO ChargeTM Product Portfolio
MicroSource products are used in many TWS designs and several parts now support HERO ChargeTM. The LP781x family are case management ICs and the LP408x are earbud charging ICs. LP4080 or LP4081 can pair with any case management IC to implement HERO ChargeTM. The LP7810 includes a linear charger tolerant to 30 V input for charging the case battery, with two independent outputs delivering up to 250 mA each for earbud charging. The LP7811 contains a high-efficiency switching charger tolerant to 30 V input with up to 1.7 A case charging current and two independent outputs up to 300 mA each for earbud charging. The LP7812 allows a single-chip implementation of HERO ChargeTM in the case without requiring an external MCU; other case management ICs require an MCU for system management.
04 HERO ChargeTM Ecosystem Partners
To reduce overall TWS system cost, MicroSource has worked with several Bluetooth SoC vendors to have linear chargers in their SoCs support HERO ChargeTM. For example, certain recent SoC generations include built-in linear charging compatible with HERO ChargeTM. Paired with any LP781x case IC, such SoCs can benefit from the increased case runtime enabled by the HERO ChargeTM scheme.
05 Conclusion
HERO ChargeTM delivers high efficiency, fast charging, and optimized power transfer. Its very low voltage difference—down to about 50 mV—lets earbuds charge at high C-rates with minimal heat, enabling fast charge without thermal issues. The saved energy remains in the charging case battery, significantly extending TWS runtime as demonstrated in the SoundPeats Capsule3 Pro. The scheme requires no MCU software intervention, reducing development effort and system cost. Charging remains linear, keeping external component count and PCB area low. When combined with SoCs that integrate compatible linear chargers, HERO ChargeTM can further reduce BOM and PCB complexity.
