Battery monitor chip daisy-chains over novel bus for high voltages

Renesas has introduced a battery pack monitor for long strings of cells that uses an ac-coupled bus to solve the thorny problem of passing data up and down the line. At the same time, it revealed a high-side battery protection and monitoring IC for 4S to 16S cell battery packs.

RAA489204 for long strings

Stackable up to 30 ICs
Up to 14-cells monitored (10 to 65V)
±10mV accuracy, ±190mV pack accuracy
Measures and sends voltages, temperatures and diagnostics for 112 cells in <10ms
Supports CoO₂ Mn₂O₄ and FePO₄ Li-ion chemistries
Daisy chain typically draws 1mA when transmitting 10% of time
Internal (10mA) and external passive cell balancing
64pad TQFP

The RAA489204’s two-wire bi-directional daisy chain is ac-coupled, dc-balanced and fully differential for maximum EMI immunity. One of three operating rates can be selected: 333kHz, 500kHz or 1MHz. Not shown in the diagram are passive components including the common-mode choke needed in some applications.

It can be used on-board or, with an un-screened twisted-pair cable (and safety components), off-board at up to 500mm range. It is not recommended for use across the systems low-voltage to high-voltage barrier, but it can be transformer-coupled to allow this – transformer coupling also removes the cable capacitance restriction, allowing connection over many metres.

CRC (cyclic reduncancy checking) ins included in the daisy-chain protocol to verify integrity for the header packet and data packets.

An 2.5Mbit/s SPI bus is provided so that the bottom IC in a string can communicate with the host microcontroller.

RAA489206 for 4S to 16S

Up to 16 cells handled (12 to 55V)
±10mV accuracy
Low-side current sense
High-side charge/discharge protection
Internal (8mA) and external (200mA) passive cell balancing
62V hot plugging
64pad QFN

The 16 cell RAA489206 operates with a pair of external mosfets for pack protection and one mosfet per cell if external balancing is needed. An external npn transistor is used with on-chip circuitry to establish the internal logic supply – the RAA489204 also uses this technique.

Communication with its host over I²C, SPI (with or without CRC).

Consumption is 200µA idling or 18µA in shipping mode.

Renesas sees both poducts being of intertest to designers of e-scooters and high-voltage power tools, and “the increasing adoption of battery management systems in the un-interruptable power supplies of the data center is spiking demand for ICs that can support higher voltage and larger cell battery pack sizes”, according to Renesas power division v-p Andrew Cowell.

Grid backup is another potential application for the daisy-chained RAA489204.

Product pages

RAA489204

RAA489206