ACT2804 datasheet(13/23 Pages) ACTIVE-SEMI

13 / 23 page

Rev 3, Apr-17-2017

Innovative Power

- 13 -

www.active-semi.com

ACT2804

APPLICATIONS INFORMATION

Fast Charge Current Control

The block diagram in Figure 2 shows how battery

current is sensed for charge current control.

Figure 2: Battery current monitoring

A small percentage of charge current is sensed and

sinked into a resistor connected at pin ICST. In

charge mode, this would allow user to set fast

charge current based on the following equation.

For

example,

IC=1A

with

RCS=25mΩ

and

RICST=8kΩ.

Recommended RICST is shown in following table:

During discharge mode, inputs of battery current

sense amp are flipped to sense discharge current,

and voltage level at pin ICST can be used (by the

system) to monitor the magnitude of discharge

current based on the following equation.

For example: VICST=0.4V with I_DISCHARGE=1A,

and RICST=8kΩ.

LED Threshold Setting

LED1, LED2, LED3 and LED4 thresholds are

adjustable with external resistors RLS1, RLS2, RLS3,

and RLS4 connected from LEDLS1, LEDLS2,

LEDLS3, LEDLS4 to APNG respectively, as shows

in Figure3.

Figure 3: LED threshold setting

The following equation shows how the external

resistor shifts the LED thresholds. The range of

LED1‐LED4 indicator threshold shift from 5.5V‐

8.8V.

VLED Example is given by the below table:

LED Hysteresis Window Setting

The adjustable LED voltage thresholds are set for

HZ mode. In charge mode, the measured battery

voltage is higher than in HZ mode, while in

discharge mode, the measured battery voltage is

lower. To have relatively better “fuel gauge” for

battery, a programmable hysteresis window will

help. When the battery voltage goes up (in charge

mode), the thresholds become higher, when the

battery voltage goes down, lower thresholds are

applied.

ACT2804 provide HYST pin to set hysteresis

window for each indication level as shows in Figure

3 .

RLSx

(kΩ)

VLEDx

(V)

8.2

43.2

7.798

49.1

7.7

7.395

7.3

67.5

7.1

RLSx

(kΩ)

VLEDx

(V)

6.7

108

6.5

120

6.4

135

6.3

180

6.1

270

5.9

)

(

)

(

)

(

1000

)

(





ICST

IC (A)

RICST

Units

RCS=25mΩ

RCS=50mΩ

0.8

kΩ

0.9

8.89

4.44

kΩ

1.0

kΩ

1.1

7.27

3.64

kΩ

1.2

6.67

3.33

kΩ

1.3

6.15

3.08

kΩ

1.4

5.71

2.86

kΩ

1.5

5.33

2.67

kΩ

)

(







ICST

DISCHARGE

ICST

)

(

)

(

108

LSx

)

(







LEDX

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