FIGURE 2. BLOCK DIAGRAM
Internal Voltage Regulator
The ISL6295 incorporates an internal voltage regulator that
supports 1-cell series lithium pack configurations. The
internal regulator draws power directly from the VP input. No
other external components are required to regulate circuit
Precision Time Base
The integrated precision time base is a highly accurate RC
oscillator that provides precise timing for the sigma-delta A/D
and for the on-chip elapsed time counters without the need
for an external crystal. This time base is trimmed during
manufacturing to a nominal frequency of 131.072kHz.
An integrated temperature sensor is provided that can
eliminate the need for an external thermistor. As an option, a
connection is provided for an external thermistor for
applications where the battery pack is physically located at a
distance from the ISL6295.
256 bytes of EEPROM memory is incorporated for storage
of non-volatile parameters such as cell models for use with
Intersil’s host driver firmware. An an initialization block with
values that are loaded into ISL6295 registers following a
power on condition. Included in this block is 16 bytes for
battery ID information.
The ISL6295 incorporates an integrating sigma-delta A/D
converter together with an analog MUX that has inputs for
charge and discharge currents, pack voltage, GPAD voltage,
the on-chip temperature sensor, and an off-chip thermistor.
The converter can be programmed to perform a conversion
with magnitude resolution of 8- to 15-bits while using either a
single 170mV or 340mV reference.
The ISL6295 incorporates four 32-bit accumulators and four
32-bit elapsed time counters. The Discharge Current
Accumulator (DCA) and the Charge Current Accumulator
(CCA) are intended to record discharge and charge capacity
values. The Discharge Time Counter (DTC) and the Charge
Time Counter (CTC) are intended to maintain the total
discharge time and charge time. Accumulated charge and
discharge values can be used to determine state of charge
of the battery as well as cycle count information. With
information provided by the elapsed time counters, average
charge and discharge currents over an extended period of
time can be calculated.
SMBus/I2C™ Communications Interface
This communications port for the ISL6295 is a 2-wire
industry-standard SMBus/I2C™ interface. All commands,
status, and data is read or written from the host system via
32 bytes of general purpose RAM memory are provided for
storage of temporary parameters.
A/D and Accumulator/Timer Operation
A/D CONVERSION CYCLE
When the A/D converter is enabled and active, it repeatedly
performs a cycle of 1 to 8 conversions as programmed by
October 25, 2005