ICS1702 datasheet(11/28 Pages) ETC

11 / 28 page

ICS1702

The maintenance mode (MMN) indicator is on when the ICS1702

is either in the topping charge, maintenance charge, direct

maintenance mode, or the condition mode. The MMN indicator is

also lit in conjunction with the OTN indicator when cold battery

charging is in progress. The maintenance mode indicator flashes at

a one second rate when the ICS1702 is controlling the discharge

portion of the discharge-to-charge or the discharge-only mode.

The polling detect (PFN) indicator is on when the ICS1702 polls

for a battery. The controller applies periodic charge pulses to detect

the presence of a battery. The indicator is a warning that these

charge pulses are appearing at the charging system terminals at

regular intervals. When a battery is detected, the indicator is turned

off.

The out-of-temperature range (OTN) indicator is active whenever

the voltage at the temperature sense (THERM) input enters a range

that indicates that the attached battery is too hot to charge. The

OTN indicator is also activated with the MMN indicator if the

controller is initialized with the battery in the cold battery charge

region.

Charge Rate Selection: SEL0, SEL1 Pins

The SEL0 and SEL1 inputs must be programmed by the user to

inform the ICS1702 of the desired charge rate. When left

unconnected (open), these tri-level pins will float to about 2.3V.

When a low level is required, the pin must be grounded. When a

high level is required, the pin must be tied to V

. The voltage

ranges for low (L), open (Z) and high (H) are listed in Table 10,

DC Characteristics. To program the SEL0 and SEL1 inputs, refer

to the Charge Rate List in Table 4.

The ICS1702 does not control the current flowing into the battery

in any way other than turning it on and off. The required current

for the selected charge rate must be provided by the user’s power

source. The external charging circuitry should provide current at

the selected charge rate. For example, to charge a 1.2 ampere hour

battery in 30 minutes (2C), approximately 2.4 amperes of current is

required.

Pin Descriptions

The ICS1702 requires some external components to control the

clock rate, sense temperature and provide an indicator display. The

controller must be interfaced to an external power source that will

provide the current required to charge a battery pack and, if

desired, a circuit that will sink discharge current.

Output Logic Signals: CHG, DCHG Pins

The CHG and DCHG pins are active high, TTL compatible

outputs. In addition to being TTL compatible, the CMOS outputs

are capable of sourcing current which adds flexibility when

interfacing to other circuitry. A logic high on the CHG pin

indicates that the charging current supply should be activated. If

applicable, a logic high on the DCHG pin indicates that the

discharge circuit should be activated.

Care must be taken to control wiring resistance and inductance.

The load resistor must be capable of handling this short duration

high-amplitude pulse. If the auxiliary discharge-to-charge mode is

selected, the power dissipation of the load resistor must be properly

selected to accept the extended length of the discharge pulse.

Indicators: CMN, MMN, PFN, OTN Pins

The controller has four outputs for driving external indicators.

These pins are active low. The four indicator outputs have open

drains and are designed to be used with LEDs. Each output can

sink over 20mA which requires the use of an external current

limiting resistor. The four indicator signals denote fast charge

stage, topping and maintenance stages, and the polling detect and

out-of-temperature range modes as shown in Table 3.

The charge mode (CMN) indicator is activated continuously during

the soft start and fast charge stages. When the controller enters the

topping charge stage, the output goes high and the indicator turns

off.

Table 3: Indicator Description List

PFN

MMN

CMN

OTN

Description

Polling detect mode

Maintenance or topping charge, direct maintenance or condition mode

Fast Charge

Hot battery shutdown

Cold Battery Charge

flash

Discharge portion of the discharge-to-charge or discharge-only mode

flash

see Applications Information

flash

see Applications Information

flash

see Applications Information

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