MAX8934CETI+T Maxim Integrated Products, MAX8934CETI+T Datasheet - Page 24

• Manufacturer Part Number: MAX8934CETI+T
• Description: IC BATTERY CHARGER DUAL 28TQFN
• Manufacturer: Maxim Integrated Products
• Series: Smart Power Selector™r

Specifications of MAX8934CETI+T

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 4.1 V ~ 6.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Dual-Input Linear Chargers, Smart Power Selector
with Advanced Battery Temperature Monitoring
When the MAX8934_ is used with a microprocessor (FP),
connect a pullup resistor between CHG and the logic I/O
voltage to indicate charge status to the FP. Alternatively,
CHG can sink up to 20mA for an LED indicator.
DONE is an open-drain, active-low output that goes low
when charging is complete. The charger enters its DONE
state 15s (60min for the MAX8934B and MAX8934D)
after the charge current falls to the charge-termination
threshold and the charger is in voltage mode. The char-
ger exits the DONE state, and fast-charge resumes, if the
battery voltage subsequently drops 104mV, or if input
power or CEN is cycled. When the MAX8934_ is used in
conjunction with a FP, connect a pullup resistor between
DONE and the logic I/O voltage to indicate charge status
to the FP. Alternatively, DONE can sink up to 20mA for
an LED indicator.
FLT is an open-drain, active-low output that goes low
during a battery fault. The fault state occurs when either
the prequal or fast-charge timer expires. The prequal
and fast-charge fault timers are set by C
While in fast-charge mode, a large system load or device
self-heating can cause the MAX8934_ to reduce charge
current. Under these circumstances, the fast-charge
timer adjusts to ensure that adequate charge time is still
allowed. Consequently, the fast-charge timer is slowed
by 2x if charge current is reduced below 50% of the pro-
grammed fast-charge level. If charge current is reduced
to below 20% of the programmed level, the fast-charge
timer is paused. The fast-charge timer is not adjusted
if the charger is in voltage mode where charge current
reduces due to current tapering under normal charging.
To exit a fault state, toggle CEN or remove and reconnect
the input source(s). Note also that thermistor out of range
or on-chip thermal-limit conditions are not considered
faults. When the MAX8934_ is used in conjunction with a
FP, connect a pullup resistor between FLT and the logic
I/O voltage to indicate fault status to the FP. Alternatively,
FLT can sink up to 20mA for an LED indicator.
24
_____________________________________________________________________________________
TOP OFF: t
FAST CHARGE: t
PREQUAL: t
−
MAX8934B and MAX8934D)
Fault Output (FLT) and Charge Timer
TO
=
PQ
15s (60 minutes for the
Charge DONE Output (DONE)
FC
=
=
30min
300min
×
0.068 F
×
C
0.068 F
CT
CT
C
F
:
CT
F
The MAX8934_ thermistor monitor is configured to
execute JEITA recommendations regarding Li+/Li-Poly
battery charging by adjusting the fast charge current
and/or the charge termination voltage accordingly (see
Figures 6 and 7). Connect the THM input to an external
negative temperature coefficient (NTC) thermistor to
monitor battery or system temperature. Since the therm-
istor monitoring circuit employs an external bias resistor
from THM to THMSW, the thermistor is not limited only
to 10kI (at +25NC). Any thermistor resistance can be
used as long as the value of R
the thermistor’s +25NC resistance. The MAX8934_ THM
thresholds are optimized for a thermistor Beta of 3964
or 3477 (see the Selector Guide). The general relation
of thermistor resistance to temperature is defined by the
following equation:
where:
Charging is suspended when the thermistor tempera-
ture is out of range (V
charge timers are also suspended and hold their state
but no fault is indicated. When the thermistor comes
back into range, charging resumes and the charge timer
continues from where it left off.
The THMEN input controls THMSW and the thermistor
monitor circuitry when the battery charger is disabled,
providing the user with the means to minimize the bat-
tery current drain caused by the thermistor monitor. The
THMEN input is ignored while the battery is charging,
since the thermistor must be monitored at all times.
While charging, the thermistor monitor is used to auto-
matically adjust the charge termination voltage and/or
the fast-charge current, depending on the sensed bat-
tery temperature and the safety region set at the factory.
If the battery temperature exceeds the THM hot overtem-
perature threshold and THMEN is high, the OT flag pulls
low. Typical systems connect OT to a FP input so that the
system can safely shut down.
R
R
A = The material constant of the thermistor
T = The temperature of the thermistor in NC
T
25
= The resistance in ohms of the thermistor at
= The resistance in ohms of the thermistor at
temperature T in Celsius
+25NC
R
T
=
R
25
×
THM_T1
e



β



T 273 C 298 C
+
> V
1
Thermistor Monitor
THMSW
°
THM
-
1
> V
°
is equivalent to



THM_T4



). The