SiP provides integrated solution for automotive battery sensing

December 13, 2012 // By Christoph Hammerschmidt
The AS8515 system-in-package (SiP) introduced today by ams AG enables the implementation of a complete automotive battery measurement system when interfaced via SPI to any microcontroller. Combining signal processing, voltage regulation and LIN transceiver in a single package, it provides accurate and linear current, voltage and temperature measurement outputs

The device is a stacked-die package consisting of a signal-processing die with two high-precision ADC channels for current, voltage and temperature measurements, and a high-voltage CMOS die providing voltage regulation, a LIN transceiver and watchdog functions. Supporting manufacturers' ISO26262 safety standard compliance processes, the device is well suited for battery management systems (BMS) for lithium-ion batteries in electric vehicles, hybrid electric vehicles and vehicles with an internal combustion engine.

Providing linear 16-bit digital outputs, the AS8515 is designed for implementing State of Charge (SoC) monitoring in automotive batteries through measurement of open-circuit voltage and coulomb counting. The device also provides highly accurate and linear conversion of small signals from other devices such as the pressure sensors used in a vehicle’s hydraulic, pneumatic or barometric systems.

By integrating voltage regulation and a LIN2.1 transceiver with signal-processing circuitry in a single package, the AS8515 provides a complete current and voltage measurement system that only requires the addition of a simple microcontroller and, for current measurement, a precision shunt resistor.

The bottom (signal processing) die in the AS8515 is the same die used in the AS8510 sensor interface chip, which ams introduced in January 2011.

Offering two independent 16-bit ADC channels, it can measure signals from sub- micro volt up to 200 mV and measure current across a range from 1 mA to 2000 A through a 100 micro Ohm shunt. All measurements are offset-free and highly linear across the device’s specified ambient temperature range (-40°C to +115°C). The two channels can be configured to measure the same input synchronously to provide a redundant design supporting functional safety.

The top die in the SiP is a system basis chip (SBC) providing voltage regulation via an LDO, an automotive-certified LIN 2.1 transceiver, and various system monitoring and protection features such as power-on reset and a window watchdog function.

The AS8515, together with external micro and its I/O ports, offers the flexibility to support use