ICS1722
Battery Detection
Discharge-to-Charge Mode
Upon power-up or after a master reset, excess charge from output
filter capacitors at the charging system terminals is removed with a
series of discharge pulses. After the discharge pulse sequence is
complete, the voltage at VIN must be greater than 0.5V when a
battery is present. If the voltage at the pin is less than 0.5V, the
ICS1722 assumes no battery is present, and the polling detect
mode is initiated. No indicator is active during the discharge
pulses.
The time required for discharge depends on the energy in the battery
and the discharge rate. The discharge is not limited by a timer. This
allows the user to set the discharge rate. The battery is drained to 1
volt/cell as read at the VIN pin under load and then the controller
enters soft start at a charge rate set by the SEL0 and SEL1 inputs. The
discharge load is activated by the DCHG pin which goes low for about
400ms every second. A resistor value selected for a 2.5C discharge
based on
1.4V/cell results in about a 1C discharge rate.
The ICS1722 enters the polling detect mode and applies a
100ms charge pulse. During the pulse, the ICS1722 monitors the
VIN pin to determine if the divided down terminal voltage is above
OPREF. If the battery is present, the voltage will be clamped below
the reference on OPREF while the current pulse is applied. If a
battery is not present, the voltage at VIN will rise above the
reference at OPREF.
The discharge-to-charge mode can be entered by placing the
AUX0 pin high (H) and the AUX1 pin low (L) with the SEL0 and
SEL1 inputs set for the desired fast charge rate. This setting initializes
the discharge sequence. The ICS1722 enters the discharge-to-charge
mode at initial power-up or with a master reset. The discharge mode
occurs first, to be followed by the selected fast charge mode. During
discharge, the MMN indicator flashes at a one second rate, while
during the soft start and fast charge stages the CMN indicator is
activated continuously.
The charge pulse will repeat until the battery is reinstalled. The
polling detect indicator (PFN) is the only indicator active as long as
the ICS1722 is in the polling detect mode. Once a battery is
installed, the ICS1722 will turn off the PFN indicator and enter the
soft start stage. The ICS1722 will automatically re-enter the
polling detect mode if the battery is removed.
Four charge modes are available after the discharge portion is complete
by changing the state of the AUX inputs during the discharge portion
of this mode. The available charge modes are:
Fast Charge: Leave the AUX inputs open (Z).
Battery Removal
During the application of a charge pulse, the voltage at the VIN pin
is compared to the voltage at the OPREF pin. If the voltage at VIN
is greater than the voltage at OPREF during the application of the
current pulse, then the battery is assumed to have been removed
and the ICS1722 enters the polling detect mode. If the voltage at
VIN is below the voltage at OPREF, charging continues.
·
Direct Maintenance Mode: Set the AUX0 low (L) and AUX1 high
(H).
·
·
·
Condition Mode: Set AUX0 high (H) and AUX1 open (Z).
Ten-Hour Timer Mode: Set AUX0 high (H) and
AUX1 high (H).
If the battery is removed while in the discharge-to-charge mode, the
ICS1722 will continually reset itself until the battery is reinstalled. See
Application Information for more information.
When in the topping charge or maintenance charge stages, a charge
pulse may not occur for several seconds. During the period
between charge pulses, the voltage at VIN must be greater than
0.5V if a battery is attached. If the voltage at VIN is less than 0.5V,
the ICS1722 assumes the battery has been removed, and the
polling detect mode is initiated.
Discharge-Only Mode
The time required for discharge depends on the energy in the battery
and the discharge rate. The discharge is not limited by a timer. This
allows the user to set the discharge rate. The battery is drained to 1
volt/cell as read at the VIN pin under load. The ICS1722 shuts down
after the discharge sequence is finished and a master reset must be
performed to reactivate the device. The discharge load is activated by
the DCHG pin which goes low for about 400ms every second. A
resistor value selected for a 2.5C discharge based on 1.4V/cell results
in about a 1C discharge rate. The discharge-only mode can be entered
by placing the AUX0 pin open (Z) and the AUX1 pin low (L). The
ICS1722 enters this mode at initial power-up or with a master reset.
During the discharge portion, the MMN indicator flashes at a one
Auxiliary Modes of Operation
The ICS1722 allows six alternate modes of operation to help
customize the charging system for certain applications. The tri-
level AUX0 and AUX1 pins are used to select the operating mode.
The AUX0 and AUX1 pins default the ICS1722 into fast charge
operation. Except for the discharge-to-charge mode, another mode
can only be selected by re-programming and resetting the
controller.
second rate.
7
GALAXY [ GALAXY POWER, INC. ]
