ACT2804
Rev 2, Feb-04-2016
APPLICATIONS INFORMATION
LEDLS3, LEDLS4 to APNG respectively, as shows
in Figure3.
Fast Charge Current Control
The block diagram in Figure 2 shows how battery
current is sensed for charge current control.
Io
Iin
Output
Cout1
Input
RHYST
RIMC
RLS2 RLS3
VIN
VOUT
RLS1
RLS4
Cin
L
ACT2804
SW
ICST
RCS
25m
BAT
RICST
CBD
Battery1
Battery2
RCBD
47
ACT2804
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.
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.
1000
Ic(A)
(1)
5*RCS (m)*RICST (k)
108k
RLSx (k)
VLEDX (V ) 5.5V
(3)
For example, IC=1A with RCS=25mΩ and
RICST=8kΩ.
Recommended RICST is shown in following table:
RLSx
VLEDx
(V)
RLSx
VLEDx
(V)
RICST
(kΩ)
(kΩ)
IC (A)
Units
RCS=25mΩ
10
RCS=50mΩ
5
72
7
40
43.2
47
8.2
8
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
90
6.7
6.5
6.4
6.3
6.1
5.9
8.89
8
4.44
4
108
120
135
180
270
7.798
7.7
7.27
6.67
6.15
5.71
5.33
3.64
3.33
3.08
2.86
2.67
49.1
57
7.395
7.3
60
67.5
7.1
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.
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.
IDISCHARGE RICST
VICST
(2)
20k
For example: VICST=0.4V with I_DISCHARGE=1A,
and RICST=8kΩ.
LED Threshold Setting
LED1, LED2, LED3 and LED4 thresholds are
ACT2804 provide HYST pin to set hysteresis
window for each indication level as shows in Figure
adjustable with external resistors RLS1, RLS2, RLS3
,
and RLS4 connected from LEDLS1, LEDLS2,
Innovative PowerTM
- 11 -
www.active-semi.com
Copyright © 2016 Active-Semi, Inc.
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
