in Sample mode as long as "Samp" bit equals ‘1’, the VP
voltage is above the VPOR threshold, and the Sample-Sleep
and Shelf-Sleep modes are not active. Run mode will be
resumed when the Samp bit is cleared to ‘0’.
The Sample mode rate is selected using the "SampDiv" bits
within the A/D Configuration Register. The sample interval is
given by (2SampDiv x 0.5) sec. The possible sample rate
intervals are as follows:
Value = 0
Value = 1
Value = 2
Value = 3
Value = 4
Value = 5
Value = 6
Value = 7
In Sample mode, much of the analog circuitry remains on.
Therefore, the power savings is not as great as in Sample-
Sleep Mode described below.
In Sample-Sleep Mode, the ISL6295 goes into sleep mode and
wakes up at a user-programmed interval to perform a set of
conversions as programmed for the A/D cycle. The purpose of
Sample-Sleep is to achieve the minimum power consumption
possible while periodically measuring specified parameters.
While the ISL6295 is in the sleep portion of the Sample-Sleep
interval, all of the analog circuitry is shut off, and the Sleep
interval time is derived from a less accurate ultra low power on-
chip oscillator that is separate from the primary oscillator.
During the active portion of Sample-Sleep Mode, a single set of
conversions is performed and RUN mode current will be
consumed for the duration of the measurements. While in
Sample-Sleep mode, the accumulation counters and timers will
still continue to run at an uninterrupted rate of 0.5s per update.
Sample-Sleep Mode is invoked by one of the following actions:
1. Cell voltage on VP drops below the trip point programmed
in the VCtrip register with the corresponding "VPent" bit set
in the TRIPctrl register (If GPAD is grounded). This action
can be used to prevent excessive battery discharge in the
event of a dangerously low cell voltage.
2. If GPAD is used for other analog input, the GPAD voltage
drops below the trip ponit programmed in the VCtrip register
with the corresponding “GPADent” bit set in the TRIPctrl
3. Setting the “SSLP” bit in the OpMode register. The host can
take this action when the system is entering a low power
standby condition, and it is desireable to periodically update
measurements for current, voltage, and/or temperature
4. Magnitude of current measurement is less than the I-trip
register value when "Ient" bit is set in the Tripctrl register.
The Sample-Sleep interval is determined by the programming
of the "SampDiv" bits within the ADconfig register, together with
the "SSLPdiv" bits within the OpMode register. The sample
interval is 2SampDivx 2SSLPdivx 0.5sec. The possible Sample-
Sleep interval time therefore ranges from a minimum of 0.5sec
to over 136 minutes.
Exit from Sample-Sleep Mode to Run mode can be
accomplished by clearing the "SSLP" bit or by programming a
wake up based on pack voltage or current. Wake up based on
charge current will occur when the "Iex" bit is set in the TRIPcntl
register and the charging current value is above the threshold
programmed in the I+trip register. Wake up based on pack
voltage will occur when the "VPex" bit is set in the TRIPctrl
register and the pack voltage rises above the threshold
programmed in the VPtrip register.
Shelf-Sleep Mode is the lowest power mode and is intended to
preserve battery capacity when the battery pack is shipped or
stored or if the battery voltage drops below a specified
threshold. While in Shelf-Sleep mode, no ADC measurement is
taken, no accumulation is performed, and no SMBus
communications are recognized. In addition, volatile memory is
Entry to Shelf-Sleep Mode is enabled by programming the
“SHELF” bit in the OPmode register to ‘1’ or "Shent" bit in the
TRIPctrl register to ‘1’ and when VP is less than SStrip. The
Shelf Sleep mode will then be entered when the SMBus pins
(both SDA and SCL) drop from a high to a low level for a
minimum time period specified by tSHELF. This action will also
occur if the battery pack is physically disconnected from the
Exit from the Shelf-Sleep mode back to Run mode will occur
when the SMBus pins (both SDA and SCL) are both pulled
from a low to a high state, and remain high for a minimum time
of tWAKE to signify system activity or connection of the pack to
General Purpose Input/Output
The NTC and GPAD pins have alternate functions of general
purpose I/O. IO0 and IO1 respectively. These pins can be
configured as digital General Purpose Inputs/Outputs if their
normal application functions of temperature and voltage
monitoring are not needed. Their configuration is controlled in
the GPIOctrl register.
The NTC/IO0 pin may be configured as a push-pull output, an
open-drain driver with internal pull-up, or as a three-stated pin.
When configured as a push-pull or open drain output, the
output high voltage is equal to the internally regulated supply
voltage, which is nominally at 3.3V. When the output function is
disabled, an external circuit may drive the pin as an input with a
voltage range of 0-3.3V. The input function may be used
whether or not the pin is driven by the ISL6295. In addition, the
input function may be disabled, in which case, the input buffer is
October 25, 2005