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 Integrated Device Technology


  • ZSSC1751 - System Basis Chip for Battery Management

  • Created: May 10, 2016

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Description

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Summary

The ZSSC1751 is a system basis chip designed for battery management. It runs with a supply voltage ranging from 4.2V up to 18V. The ZSSC1751 typically consumes around 12mA during normal mode and approximately 60uA during sleep mode. The device has two input channels that are used to measure the current, voltage, and temperature of the battery. Each of these channels has its own 24-bit sigma-delta analog-to-digital converter (ADC) that has a maximum sampling rate of 16kHz. The ZSSC1751 provides an SPI port wherein the microcontroller can access and read its registers as well as its one-time programmable memory.


In this reference design, the ZSSC1751 device is powered directly by the battery through its VDDE pin. All internal regulators of ZSSC1751 are connected directly to VDDE. The current, voltage, and temperature of the battery are measured by the ZSSC1751 device through its two channel inputs. The current of the battery is measured by one of the two input channels that is connected to pin INP and pin INN. The voltage drop across Rshunt serves as the reference for that input channel to determine the current drawn from the battery. The voltage and temperature of the battery are measured by the second input channel through the VBAT, NTH, and NTL pins. The voltage drop across the thermistor Rntc serves as the reference for that channel to know the temperature of the battery. The other pins of the ZSSC1751 device are categorized into three categories: digital IOs, microcontroller supply pins, and power state indicator pin. The digital I/O pins is composed of the SPI port pins (CSN, SCLK, MOSI, MISO), MCU clock pin (MCU_CLK), reset pin (MCU_RSTN), watchdog timer disable pin (WDT_DIS), interrupt pin (IRQN) and digital ground pin (VSSN). The VDDC and VDDP pin which outputs 1.8V and 3.3V respectively, serves as a power supply for an external MCU. The SLEEPN pin belongs to the power state indicator pin category. It can be used as a disable signal for external regulators.


The ZSSC1751 simultaneously measures the voltage and current of the battery. In this way, it is possible to find out the internal resistance of the battery which is correlated to its state-of-health (SOH). The state-of-charge (SOC) and the state-of-function (SOF) of the battery can also be determined by integrating the current of the battery. The ZSSC1751 chip is really useful in applications such as intelligent battery monitoring in automotive (start/stop systems, e-bikes, scooters, and e-carts), industrial, medical and photovoltaic applications.