MAX8934GETI+ Maxim Integrated Products, MAX8934GETI+ Datasheet - Page 22

• Manufacturer Part Number: MAX8934GETI+
• Description: IC LI BATT CHARGER DUAL 28TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8934GETI+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 3. Package Thermal Characteristics
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
+25NC). Any thermistor resistance can be used as long
as the value of R
+25NC resistance. The MAX8934G THM thresholds are
optimized for a thermistor Beta of 3964. The general rela-
tion of thermistor resistance to temperature is defined by
the following equation:
where:
Charging is suspended when the thermistor temperature
is out of range (V
The 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
22
R
R
A = The material constant of the thermistor
T = The temperature of the thermistor in NC
T
25
_____________________________________________________________________________________
Continuous Power
= The resistance in ohms of the thermistor at
= The resistance in ohms of the thermistor at
Dissipation
temperature T in NC
+25NC
R
B
B
T
JC
JA
=
R
THMSW
THM_T1
25
×
e



is equivalent to the thermistor’s
β
< V



T 273 C 298 C
+
THM
SINGLE-LAYER PCB
1666.7mW
(derate 20.8mW/NC above +70NC)
48NC/W
3NC/W
1
°
or V
-
THM
1
°






< V
THM_T4
).
28-PIN 4mm x 4mm THIN QFN
the fast-charge current, depending on the sensed bat-
tery temperature. If the battery temperature exceeds the
THM hot overtemperature 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.
The ultra-low quiescent current LDO is always on and is
preset to an output voltage of 3.3V. The LDO provides up
to 30mA output current. When DC and USB are invalid
and the battery is discharging, the LDO output volt-
age tracks V
capacitor connected from LDO to GND is recommended
for most applications.
Good design minimizes ground bounce and voltage
gradients in the ground plane. GND should connect to
the power-ground plane at only one point to minimize the
effects of power-ground currents. Battery ground should
connect directly to the power-ground plane. Connect
GND to the exposed pad directly under the IC. Use mul-
tiple tightly spaced vias to the ground plane under the
exposed pad to help cool the IC. Position input capaci-
tors from DC, SYS, BATT, and USB to the power-ground
plane as close as possible to the IC. Keep high current
traces such as those to DC, SYS, and BATT as short and
wide as possible. Refer to the MAX8934A Evaluation Kit
for a suitable PCB layout example.
SYS
MULTILAYER PCB
2285.7mW
(derate 28.6mW/NC above +70NC)
35NC/W
3NC/W
as it drops below 3.3V. A 1FF ceramic
PCB Layout and Routing
Power Dissipation
Always-On LDO