ACT2804
Rev 2, Feb-04-2016
APPLICATIONS INFORMATION
HYST pin is regulated at 1V. Its input current will
determine hysteresis adjustment equally to all level.
Connect HYST to APGN via a resistor to set
hysteresis window.
TH voltage. The ACT2804 compares the voltage at
the TH pin with the internal VTHH and VTHL
thresholds to determine if charging or discharging is
allowed. When VTH<VTHL or VTH >VTHH, it will be
triggered latch off fault, there is 3 ways to wake up
ACT2804 when VTH returns to the normal range.
Beside the hysteresis window, to avoid comparison
oscillation, fixed 100mV of hysteresis is added to
each LEVEL comparator.
1. Push PB when latch off bit is not set
2. I2C to clear faults in standby
3. Plug Vin to power up
Hysteresis window is given by below equation:
54K
ICHG=140uA
ACT2804
HYST(V )
4
VTCL=1V
RHYST
K
+
CHG_HOT
–
VHYST 4:3 0.5* HYST
VHYST 2:1 0.6* HYST
5
+
CHG_COLD
VTCH=2.5V
Li+ Battery
Pack
Rb
–
TH
IDIS=100uA
VTDL=0.57V
Then RHYST Example is given by the below table:
+
DIS_HOT
LED1
LED2
LED3
VHYST
LED4
VHYST
RHYST (kΩ)
–
VHYST
VHYST
Ra
+
Floating
270
135
90
0mV
0mV
0mV
0mV
NTC
DIS_COLD
VTDH=2.5V
–
120mV
240mV
360mV
480mV
600mV
720mV
120mV
240mV
360mV
480mV
600mV
720mV
100mV
200mV
300mV
400mV
500mV
600mV
100mV
200mV
300mV
400mV
500mV
600mV
Figure 4: Thermistor setting
67.5
54
VTCL ICHG Rchot
V TCH ICHG Rcold
(7)
(8)
45
Battery Impedance Compensation
To avoid the number of LEDs changes between
charge and discharge modes. Internal impedance
compensation circuit is built in. An external resistor
is used to set the impedance from 100mΩ to
800mΩ. RIMC is corresponding to battery
impedance. The LED1-4 thresholds shifted up and
down based on the product of charge/discharge
current and set impedance. RIMC value is given by
below equation.
Ra RNTCh
Ra RNTCh
Rchot Rb
Rcold Rb
(9)
Ra RNTCc
Ra RNTCc
(10)
RNTCc : NTC Resistor at cold temperature (Tcold)
RNTCh : NTC Resistor at hot temperature (Thot)
From (7) (8) (9) and (10) calculate Ra and Rb in
charge mode, as the same method, the resistors in
discharge mode can be calculated.
RCS (m)
RBAT (m)
RIMC (k) 2160k
(6)
For example, use NXRT15XH103 NTC resistor, the
In case not using compensation, float RIMC then
there is no compensation affects to trig-points.
temperature in charge mode is 0℃ to 45℃,we
RIMC example is given by the below table:
know RNTCC=27.219k and 4.917k at 0℃ to 45℃,
respectively. We can calculate Ra=33kΩ and
Rb=2.87kΩ based on the above formulas. As the
same method we can calculate the value when the
RBAT (mΩ)
RCS = 25 mΩ
RCS = 50 mΩ
100
200 300 400 500 600 700
540k 270k 180k 135k 108k 90k 77k
1280k 540k 360k 270k 216k 180k 154k
temperature is -20℃ to 60℃.
BATTERY TEMPERATURE MONITERING
LED Indication
The ACT2804 monitors the battery pack
temperature by measuring TH voltage at the TH pin
as shows in Figure 4. The TH pin is connected to
the thermistor resistor net which includes a negative
-temperature coefficient thermistor. An internal
current source provides a bias current to generate
ACT2804 is designed 5 levels of PT pin voltage into
5 application patterns. A resistor is connected from
PT pin to ground and the voltage at PT pin
programs the LED indication patterns.
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