ACT2801/ACT2801B/ACT2801C
Rev 9, 14-Mar-17
FUNCTIONAL DESCRIPTION
ACT2801/ACT2801B/ACT2801C is
battery charging and discharging
a
complete
power
operation flow chart as shown in Figure 1, and
ACT2801B system operation flow chart as shown in
Figure 2.
management solution for applications of single-cell
lithium-based backup battery pack or power bank.
There is a power path from input to output with
programmable input current limit. When output is
over loaded, the input switch Q1 starts going into
linear mode and thus output voltage starts to drop.
If output voltage drops below 4.25V, the input
switch Q1 turns off and restart in 2 seconds.
Any transitions between boost mode and charge
mode go through HZ mode by turning off all the
switches Q1-Q3 into HZ mode for 2 seconds before
enabling the other mode.
The modes are determined by HZ pin and VIN pin
as shown in the table 1. A valid VIN voltage forces
ACT2801/ACT2801B/ACT2801C into charge mode.
Boost mode is enabled if HZ pin is pulled low and
VIN is invalid or not present. For ACT2801/
ACT2801B, when HZ=0, if PB is pulled low for more
than 30ms, boost converter is enabled. For
ACT2801, during boost on, if PB is pressed more
than 1.5s, boost converter will be off.
With
the
advanced
ACT2801/ACT2801B/
ACT2801C architecture, a synchronous buck/boost
converter is connected from VOUT to switching
node (SW). With the bidirectional architecture, the
converter could be configured as either buck to
charge battery or boost to discharge battery. With
switching charger and discharger, the higher charge
Table 1: Mode Selection
current and higher conversion
achieved.
efficiency are
HZ PIN
VIN Valid
Mode
0
0
0
1
1
0
1
1
Modes of Operation
ACT2801/ACT2801B/ACT2801C has 3 operation
modes: charge mode, boost mode and high-
impedance (HZ) mode. In charge mode, the input
current limit Q1 is enabled and Q2 and Q3 operate
as a buck converter to charge battery. In boost
mode, Q2 and Q3 operate as boost converter to
step battery voltage up to +5V at VOUT, and the
current limit switch Q1 is turned off, and the reverse
current from VOUT to VIN is blocked. In HZ mode,
all the switches are turned off and the drainage
current from battery is very low. ACT2801 system
Boost
Charge
HZ
Charge
Flashlight
ACT2801B has an flashlight function. Once PB is
pressed for 3 seconds, the flashlight is switched on.
The driver will deliver up to 50mA current to the
flashlight. During flashlight on, if PB is pressed for 3
seconds, flashlight will be switched off.
Figure 1:
ACT2801 System Operation Flow Chart
LED Charge Status and
Battery Level Indication
VIN Invalid and HZ=0
Taking 2s
VIN Valid
Boost Mode
(VOUT=5V)
Charge Mode
(4.5V<VIN<5.5V)
Taking 2s
P
B
i
s
p
r
e
s
s
e
d
f
o
:
r
3
0
h
m
s
t
s
i
m
W
0
3
0
r
=
o
Z
f
H
d
r
HZ: 0—>1 or HZ=0
e
V
o
s
LED Battery Level
Indication Turns on
for 5s
V
I
s
N
with: Vbat < 2.9V or PB
is pressed for 1.5s or
Iout < 40mA for 16s
0
I
e
r
N
V
>
I
a
—
n
p
l
1
v
i
d
s
a
:
i
l
i
Z
d
B
H
a
P
n
d
H
Z
=
1
s
m
0
HZ Mode
(Ibat<10µA)
3
r
o
f
d
e
s
s
e
r
p
s
i
B
P
Innovative PowerTM
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