CS1702 datasheet(9/28 Pages) ETC

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ICS1702

Battery Detection

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

ICS1702 assumes no battery is present, and the polling detect

mode is initiated. No indicator is active during the discharge

pulses.

The ICS1702 enters the polling detect mode and applies a

100ms charge pulse. During the pulse, the ICS1702 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 charge pulse will repeat until the battery is reinstalled. The

polling detect indicator (PFN) is the only indicator active as long as

the ICS1702 is in the polling detect mode. Once a battery is

installed, the ICS1702 will turn off the PFN indicator and enter the

soft start stage. The ICS1702 will automatically reenter the polling

detect mode if the battery is removed.

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 ICS1702 enters the polling detect mode. If the voltage at

VIN is below the voltage at OPREF, the charging mode continues.

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 ICS1702 assumes the battery has been removed, and the

polling detect mode is initiated.

Auxiliary Modes of Operation

The ICS1702 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 ICS1702 into fast charge

operation. Except for the discharge-to-charge mode, another mode

can only be selected by re-programming and resetting the

controller.

Discharge-to-Charge 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 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 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 ICS1702 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.

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).

•

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

ICS1702 will continually reset itself until the battery is reinstalled. See

Application Information for more information.

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 ICS1702 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

ICS1702 enters this mode at initial power-up or with a master reset.

During the discharge portion, the MMN indicator flashes at a one

second rate.

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