case study # 03

Battery Charge Monitor IC (Gas Gauge)


Sometimes even when you have an internal team that might be able to do the job, you need to go to outside experts to ensure mission-critical success. In this case, a company that specializes in integrated circuit for power management engaged Kapik. We were invited to contribute to a “gas gauge” SoC for rechargeable batteries used in consumer mobile devices. The gauge would measure remaining power and the power consumption rate of the battery.

This project marked the company’s entry into the battery management business – and this SoC would shape its reputation in this marketplace. A new project director was brought in to lead the entry and had experience with the challenges of these types of SoCs. While he had access to an internal analog design team, he had concerns about getting the analog front-end right – having previously worked with a specialist team that took five tries to deliver a marginal product.

Kapik was recommended to the project director by satisfied past customers. He then performed his own diligence and determined that Kapik was well qualified to do the complicated analog design work for the gas gauge SoC. The company’s management team concurred; they recognized that outsourcing the analog/mixed-signal design work for this project would be essential for the long-term success of this chip development program.

Because of this and the integrated nature of SoCs, the project involved a high degree of collaboration. Kapik’s design efforts focused on analog elements and the client took care of the digital. The analog design needed 16 bits; it had to sense below Vss; signal levels are low; it needed to sense multiple channels. In addition it needed to meet the following requirements:

  • Low power: This was the most critical requirement. Our customer had a total power budget of 100µA for the analog front end.
  • High accuracy: The IC needed to provide the end user of the device with precise, real-time information on the remaining power.
  • Meet target Analog-to-Digital Converter (ADC) specification: Our customer sought 30uA active current consumption at 32KS/s and 16-bit conversion resolution. The ADCs needed to also be capable of handling negative input voltage, which would necessitate a new design technique.
  • Adaptable to environmental changes: The IC needed to remain reliable and adaptable to changes in temperature.

To resolve these challenges and constraints, Kapik developed a mixed signal system comprising of two ADCs, a high precision, tunable oscillator, a voltage regulator and other supporting circuitry. Our approach involved:

  • Developing and testing a new ADC design: The design we developed was able to handle negative input voltage capability and ensure proper transistor operation without requiring an on-chip negative charge pump and reduced the die area.
  • Developing a high precision tunable oscillator: This would enable the IC to adapt to environmental changes.

Kapik’s work didn’t stop with delivering the design. To help our client minimize their time-to-market while mitigating risk, we sent a team on-site to help with production testing, leveraging our knowledge of the design to troubleshoot and resolve issues. We also worked closely with the customer’s engineering team in developing test firmware and calibration algorithms to fine-tune analog performance. In the end, our client successfully delivered the chip to the marketplace and shipped significant volumes. And we met their high expectations by delivering an innovative design and exemplary customer service.

Interested in finding out more about our expertise in consumer electronics or learning about how we can help you? Contact us today.