8

ICS1700A

Indicators: CMN, PFN, OTN Pins

The controller has three outputs for driving external indicators.

These pins are active low. The three 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 three indicator signals denote fast charge

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

battery fault and out-of-temperature range modes as shown in

Table 1.

The charge mode (CMN) indicator is activated continuously during

the soft start and fast charge stages. The CMN indicator flashes at a

one-second rate when the ICS1700A is applying a topping or

maintenance charge.

The polling fault (PFN) indicator is on when the ICS1700A polls

for a battery for the first 10 seconds. 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 indicator is also active if

the battery is removed from the system, warning that a fault has

occurred.

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 CMN indicator if the

controller is initialized with the battery in the cold battery charge

region.

Pin Descriptions

The ICS1700A 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.

Table 1: Indicator Description List

PFN

CMN

OTN

Description

On

Polling mode or battery fault

Flash

Maintenance and topping charge

On

Fast charge

On

Hot battery shutdown

Flash

On

Cold battery charge

On

on

See Applications Information

On

One flash

See Applications Information