Datasheet

23Maxim Integrated
1.2A Switch-Mode Li+ Chargers with ±22V Input
Rating and JEITA Battery Temperature Monitoring
MAX8900A/MAX8900B/MAX8900C
Done State
The MAX8900_ enters its done state after the charger
has been in the top-off state for t
TO
. In this state, the
switching charger is off and no current is delivered to
the battery. Although the charger is off, the SETI and
DNI pins are biased in the done state and the MAX8900_
consumes the associated current from the battery (I
BAT
= 1.5V/R
SETI
+ 1.5V/R
DNI
+ 3FA). If the system load
presented to the battery is low (<< 100FA), then a typi-
cal system can remain in the done state for many days.
If left in the done state long enough, the battery voltage
decays below the restart threshold (V
RSTRT
) and the
MAX8900_ transitions back into the fast-charge state.
There is no soft-start (di/dt limiting) during the done-to-
fast-charge state transition.
Timer Fault State
The timer fault state occurs when either the prequalifica-
tion or fast-charge timers expire, or SETI/DNI is shorted
to ground (see the Setting the Fast-Charge Current
(SETI) and Setting the Prequalification Current and Done
Threshold (DNI) sections for more details). In this state
the charger is off. The charger can exit the timer fault
state by either cycling CEN or input power.
Battery Hot/Cold State
The battery hot/cold state occurs when the MAX8900_ is
in any of its charge states (dead battery, prequalification,
fast-charge, top-off) and thermistor temperature is either
less than T1 or greater than T4. In this state, the charger
is off and timers are suspended. The MAX8900_ exits
the temperature suspend state and returns to the state
it came from once the thermistor temperature is greater
than T1 and less than T4. The timer resumes once the
MAX8900_ exits this state.
V
IN
Too High State
The V
IN
too high state occurs when the MAX8900_ is in
any of its charge states (dead battery, prequalification,
fast-charge, top-off) and V
IN
exceeds V
OVLO
. In this
state, the charger is off and timers are suspended. The
MAX8900_ exits the V
IN
too high state and returns to the
state it came from when V
IN
decreases below V
OVLO
.
The timer resumes once the MAX8900_ exits this state.
Charge Timer (CT)
As shown in Figure 7, a fault timer prevents the battery
from charging indefinitely. In the dead-battery, prequali-
fication, and fast-charge states, the timer is controlled
by the capacitance at CT (C
CT
). The MAX8900_ sup-
ports values of C
CT
from 0.01FF to 1.0FF. Calculate the
prequalification time (t
PQ
) and fast-charge time (t
FC
) as
follows (Figure 9):
CT
PQ
C
t 30min
0.1 F
= ×
F
CT
FC
C
t 180min
0.1 F
= ×
F
The top-off time (t
TO
) is fixed at 16s:
TO
t 16s=
Connect CT to GND to disable the prequalification/dead-
battery and fast-charge timers. With the internal timers of
the MAX8900_ disabled, an external device, such as a
FP can control the charge time through the CEN input.
Thermal Management
The MAX8900_ is packaged in a 2.44mm x 2.67mm x
0.64mm, 0.4mm pitch WLP package and withstands
a junction temperature of +150NC. The MAX8900_ is
rated for the extended ambient temperature range from
-40NC to +85NC. Table 1 and Application Note 1891:
Wafer-Level Packaging (WLP) and Its Applications
(www.maximintegrated.com/ucsp) show the thermal
characteristics of this package. The MAX8900_ uses
Figure 9. Charge Times vs. C
CT
CHARGE TIMES
vs. CHARGE TIMER CAPACITOR
C
CT
(nF)
CHARGE TIMES (min)
800
t
PQ
t
FC
600200 400
2000
1800
1600
1400
1200
1000
800
600
400
200
0
0 1000
C
CT
(nF)
t
PQ
(min)
t
FC
t
TO
(s)
(min) (hrs)
68 20.4 122.4 2 16
100 30.0 180.0 3 16
150 45.0 270.0 4.5 16
220 66.0 396.0 6.6 16
470 141.0 846.0 14.1 16
1000 300.0 1800.0 30.0 16