ACT2823
REV 1, 01-DEC-2016
Charging LED
Threshold - Rising
RCS (m)
RIMC (k)
VIMC (mV ) 2160k IBAT
(5)
100mV Internal
Hysteresis
Charging LED
Threshold - Falling
As an example, if RCS=50mΩ, RIMC=216kΩ, and the
battery charging current is 1.5A, then the ACT2813
increases the LED voltage threshold by 750mV.
VIMC
VHYST
VLEDx
LED Hysteresis Window Setting
The LED Hysteresis Window compensates for the
increase and decrease in battery voltage associated
with charging and discharging. It provides fixed voltage
adjustment to the LED threshold settings. When in the
battery is charging, the LED threshold settings are
increased by the LED hysteresis voltage. When the
battery is discharging, the LED threshold settings are
decreased by the LED hysteresis voltage. This setting
has no effect in HZ Mode. Connecting a resistor
between the HYST pin and AGND program the
hysteresis between adjusts for battery impedances
between 0mV and 720mV. Note that the ACT2823 has
100mV of built in hysteresis that cannot be changed.
VHYST
Discharging LED
Threshold - Rising
VIMC
100mV Internal
Hysteresis
Discharging LED
Threshold - Falling
Figure 6: LED threshold setting
BATTERY TEMPERATURE MONITERING
The following equations calculate the proper RHYST
resistance. Note that LED1 and LED2 use one equation
while LED3 and LED4 use another equation.
The ACT2823 monitors the battery pack temperature by
measuring the voltage at the TH pin. The TH pin is
connected to the thermistor resistor network which
includes a negative temperature coefficient thermistor.
An internal current source provides a bias current to
generate a voltage on the TH pin. The ACT2823
compares the voltage at the TH pin with the internal
VTHH and VTHL thresholds to determine if charging or
discharging is allowed. Charging latches off and triggers
a fault in the I2C register 0x08h when VTH<VTHL or
VTH >VTHH. Charging cannot be started until the fault
condition goes away. After VTH returns to the normal
range, one of the following three conditions can restart
charging.
32.4k
HYST1:2 (V )
27k
RHYST1:2
R HYST 3:4
k
(6)
(7)
V
k
V
HYST 3:4 (V )
Where VHYST is the desired LED hysteresis in volts.
RHYST(1) = 54kΩ to set LED1 hysteresis equal to 600mV.
RHYST(3) = 45kΩ to set LED3 hysteresis equal to 600mV.
The following table provides RHYSTvalues for different
hysteresis voltages.
1. Assert PB when the latch off bit in register 0x05h = 0
2. Clear the fault status bits in register 0x08h standby
3. Recycle input power
LED1
VHYST
LED2
VHYST
LED3
VHYST
LED4
VHYST
RHYST (kΩ)
ICHG=140uA
ACT2823
Floating
270
135
90
0mV
0mV
0mV
0mV
VTCL=1V
+
CHG_HOT
120mV
240mV
360mV
480mV
600mV
720mV
120mV
240mV
360mV
480mV
600mV
720mV
100mV
200mV
300mV
400mV
500mV
600mV
100mV
200mV
300mV
400mV
500mV
600mV
–
+
CHG_COLD
67.5
54
VTCH=2.5V
Li+ Battery
Rb
–
TH
IDIS=100 uA
Pack
45
VTDL=0. 57V
+
–
DIS_HOT
NTC
Ra
LED Trigger Voltage
+
–
DIS_COLD
The battery voltage that triggers each LED to turn on
and off is a function of the LED voltage threshold, the
impedance compensation voltage, the LED hysteresis
setting, and whether the battery is charging or
discharging. The figure below graphically shows the
LED trip points as a function of these inputs.
VTDH=2.5V
Figure 7: Thermistor Resistor Network
R
NTCc : NTC Resistor at cold temperature (Tcold)
NTCh : NTC Resistor at hot temperature (Thot)
R
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16
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
