2

ICS1708

Pin Configuration

8-Pin DIP or SOIC

Pin Definitions

Pin

Name

Type

Definition

1

CHG

OUT

Active high (PFET), active low (NFET) 25mA max. TTL compatible signal used to turn on and off an external current source to

provide pulsed current to charge the battery.

2

CMN

OUT

Charge mode indicator. NFET drain rated at 40mA max. turns on an external indicator to show the controller is applying either a

3

MMN

OUT

Maintenance mode indicator. NFET drain rated at 40mA max. turns on an external indicator showing the battery is ready to use as the

topping charge or maintenance charge is applied.

4

VSS

Ground.

5

RC

IN

An external resistor and capacitor sets the frequency of the internal clock.

6

OPREF

IN

Open circuit (no battery) voltage reference. A pull down or external resistor divider from 5V sets a voltage reference on this pin used

to detect the presence of a battery.

7

VIN

IN

Battery voltage normalized to one cell with an external resistor divider.

8

VDD

Device supply =+5.0 VDC +/- 5% regulated. The ICS1708 requires 11mA max. average that includes brief 50mA peak currents.

When used, LEDs, pull-up resistors, and drivers require additional current from the +5VDC supply. An electrolytic and ceramic

capacitor between (or very close to) both VDD and VSS is recommended for bypassing.

Note:

Pin 6 has an internal pull-up.

Input and output pins have internal ESD protection diodes to VDD and VSS for 2KV protection per MIL STD 883 method 3015.7.

Controller Operation

Charging Stages

The charging sequence consists of four stages. The application of current is shown graphically in Figure 1. The

increases current levels up to the user selected fast charge rate during the first two minutes. The

charge stage, which continues until termination. After fast charge termination, a reduced duty cycle topping charge is applied, followed by

a further reduced cycle maintenance charge. After fast charge termination, the battery is charged and ready to use.

Figure 1: Graphical representation of average current levels during the four charging stages

(

S tage 3

S tage 4

S tage 2

S tage 1

0

2 m in

term ination

term ination +

C urrent

not to scale)

A verage

Tim e (not to scale)

Fast Charge

Topping Charge

2.5 to 20%

Maintenance Charge

0.6 to 5%

97%

18%

ICS1708

CHG

VDD

1

2

3

4

5

6

7

8

MMN

CMN

VIN

OPREF

RC

VSS