ISL94212_15 Datasheet, PDF (21/96 Pages) Intersil Corporation – Multi-Cell Li-Ion Battery Manager

ISL94212
Device Description and
Operation
The ISL94212 is a Li-ion battery manager IC that supervises up
to 12 series connected cells. Up to 14 ISL94212 devices can be
connected in series to support systems with up to 168 cells. The
ISL94212 provides accurate monitoring, cell balance control,
and diagnostic functions. The ISL94212 includes a voltage
reference, 14 bit A/D converter and registers for control and
data. An external microcontroller communicates to the ISL94212
through an SPI interface. Series connected ISL94212 devices
communicate to each other via a proprietary daisy chain
communications interface.
The ISL94212 devices handle daisy chain communications
differently depending on their position within the daisy chain. The
ISL94212 at one end of the daisy chain acts as a master device
for communication purposes. The master device, also called the
bottom device, occupies the first position in the daisy chain and
communicates to a host microcontroller using an SPI interface. A
single daisy chain port then connects the master device to the
next device in the daisy chain.
The device at the other end of the daisy chain from the master is
the top device. The top device has a single daisy chain port
connection to the device below. Devices other than the master
and top devices are middle devices. Middle devices have two
daisy chain port connections. The up port connects to the device
above while the down port connects to the device below. The
master ISL94212 device is device number 1. The top device is
device number n, where n equals the total number of ISL94212
devices in the daisy chain. The middle devices are numbered 2 to
(n-1) with device number 2 being connected to the master device.
If n = 2, then there is a master device and a top device, with no
middle device.
When multiple ISL94212 devices are connected to a series of
cells, their power supply domains are normally non-overlapping.
The lower (VSS) supply of each ISL94212 nominally connects to
the same potential as the upper (V_BAT) supply of the ISL94212
device below.
The ISL94212 provides two multiple parameter measurement
“scanning” modes in addition to single parameter direct
measurement capability. These scanning modes provide pseudo
simultaneous measurement of all cell voltages in the stack. In
daisy chain applications all measurement data is sent with the
corresponding device stack address (the position within the daisy
chain), parameter identifier, and data address. In stand alone
applications (non-daisy chain) data is sent without additional
address information. This maximizes the throughput for full
duplex SPI operation. Daisy chain communication throughput is
maximized by allowing streamed data (accessed by a “read all
data” address).
The addressed device, the top device and the bottom device act
as masters for the purposes of communications timing. All other
devices are repeaters, passing data up or down the chain.
The only filtering applied to the ADC measurements is that
resulting from external protection circuits and the limited
bandwidth of the measurement path. No additional filtering is
performed within the part. This arrangement is typically needed
to maintain timing integrity between the cell voltage and pack
current measurements. The ISL94212 does not measure current.
The system performs this separately using other measurement
systems. However, the ISL94212 does apply filtering to the fault
detection systems.
Power Modes
The ISL94212 has three main power modes: Normal mode,
Sleep mode and Shutdown mode (“off”).
Sleep mode is entered in response to a Sleep command or after
a watchdog timeout. Only the communications input circuits, low
speed oscillator and internal registers are active in Sleep mode,
allowing the part to perform timed scan and balancing activity
and to wake up in response to communications.
Drive the enable pin low to place the part in Shutdown mode.
When entering Shutdown mode, the internal bias for most of the
IC is powered down except digital core, sleep mode regulators,
and digital input buffers. When exiting, the device powers up and
does not reload the factory programmed configuration data from
EEPROM.
The Normal mode consists of an Active state and a Standby
state. In the Standby state, all systems are powered and the
device is ready and waiting to perform an operation in response
to commands from the host microcontroller. In the Active state,
the device performs an operation, such as ADC conversion, open
wire detection, etc.
Measurement Modes
The ISL94212 provides three types of measurement modes.
• Scan Once
• Scan Continuous
• Measure
In Scan Once mode the part performs the requested scan a
single time. In Scan Continuous mode the ISL94212 performs
repeated scans at intervals controlled by registers settings.
Measure mode allows a single parameter to be measured.
The ISL94212 ignores a Scan or Measure command, when the
device is already in a scan mode or measure mode. But, the
command passes through to other devices in the daisy chain. All
other communications functions respond normally while the
device is scanning or measuring.
Measurement Mode Commands
Measurement modes are activated by commands from an
external microcontroller. The ISL94212 uses a memory mapped
command structure. Commands are sent to the device using a
memory read operation from a specific address. The addresses
for the measurement mode commands¹ are shown in Table 1.
There are other commands that perform other actions, but these
are discussed in other sections.
1. In this document, the terminology for a hex value (e.g., h0000) is modified by a
leading value (e.g., 16’) which defines the number of bits. For the measurement
mode command address, a value of 6’h02 refers to a binary value of ‘00 0010’.
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FN7938.1
April 23, 2015