Datasheet

MAX8819A/MAX8819B/MAX8819C
PMIC with Integrated Chargers and Smart
Power Selector in a 4mm x 4mm TQFN
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• The battery charger is enabled by the processor dri-
ving the CEN input high. A valid input must be avail-
able at DC. The battery charger is disabled without
a valid input at DC or by driving CEN low.
• The system current has priority over the battery
charger; the battery charger automatically reduces
its charge current to maintain the input current limit
while still providing the system current (I
SYS
).
• The input current limit is tapered down from full cur-
rent to zero current when the die temperature transi-
tions from +100°C to +120°C. Since I
SYS
has priority
over the battery charge current, the battery charge
current tapers down before I
SYS
. The overall result is
self-regulation of die temperature (see the Thermal
Limiting and Overload Protection section for more
information).
• The battery charger stops charging in done mode
as shown in Figures 2 and 3.
Charge Status Output (CHG)
CHG is an open-drain, active-low output that indicates
charger status. As shown in Figures 2 and 3, CHG is
low when the charger is in its prequalification or fast-
charge states. When a timer count is exceeded in
either state, CHG indicates the fault by blinking at a
2Hz rate and remains in that state until the charger is
reset by CEN going low, removal of DC or setting
DLIM[1:2] = 11.
When the MAX8819_ is used with a microprocessor
(μP), connect a pullup resistor between CHG and the
system logic voltage to indicate charge status to the
μP. Alternatively, CHG sinks up to 20mA for an LED
charge indicator.
If the charge status output feature is not required, con-
nect CHG to ground or leave unconnected.
Charge Timer
As shown in Figure 3, a fault timer prevents the battery
from charging indefinitely. In prequalification mode, the
charge time is internally fixed to 33min.
t
PREQUAL
= 33min
In fast-charge mode, the charge timer is internally fixed
to 660min.
t
FSTCHG
= 660min
When the charger exits fast-charge mode, a fixed
33min top-off mode is entered:
t
TOPOFF
= 33min
While in the constant-current fast-charge mode (Figure
2), if the MAX8819_ reduces the battery charge current
due to its internal die temperature or large system loads,
it slows down the charge timer. This feature eliminates
nuisance charge timer faults. When the battery charge
current is between 100% and 50% of its programmed
fast-charge level, the fast-charge timer runs at full
speed. When the battery charge current is between
50% and 20% programmed fast-charge level, the fast-
charge timer is slowed by 2x. Similarly, when the bat-
tery charge current is below 20% of the programmed
fast-charge level, the fast-charge timer is paused. The
fast-charge timer is not slowed or paused when the
charger is in the constant voltage portion of its fast-
charge mode (Figure 2) where the charge current
reduces normally.
FAST-CHARGE, PREQUALIFICATION, AND TOP-OFF
CURRENT vs. CHARGE-SETTING RESISTOR
R
CISET
(kΩ)
CURRENT (mA)
0 5 10 15 20
1
10
100
1000
10,000
I
PREQUAL,
I
TOPOFF
I
CHGMAX
Figure 4. Calculated Charge Currents vs. R
CISET
R
CISET
(kΩ)
I
CHGMAX
(mA)
I
PREQUAL
(mA)
I
TOPOFF
(mA)
3.01 1000 100 100
4.02 746 75 75
4.99 601 60 60
6.04 497 50 50
6.98 430 43 43
8.06 372 37 37
9.09 330 33 33
10 300 30 30
11 273 27 27
12.1 248 25 25
13 231 23 23
14 214 21 21
15 200 20 20
Table 2. Calculated Charge Currents vs.
R
CISET