MAX8900BEWV+T Maxim Integrated Products, MAX8900BEWV+T Datasheet - Page 24

• Manufacturer Part Number: MAX8900BEWV+T
• Description: IC LI-ION/POLY BATT CHRGR 30WLP
• Manufacturer: Maxim Integrated Products

Specifications of MAX8900BEWV+T

• Function: Battery Monitor
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 3.4 V ~ 8.7 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 30-WLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1.2A Switch-Mode Li+ Chargers with ±22V Input
Rating and JEITA Battery Temperature Monitoring
Table 1. 2.44mm x 2.67mm x
0.64mm, 0.4mm Pitch WLP Thermal
Characteristics
thermal management techniques to prevent excessive
battery and die temperatures.
The MAX8900_ adjusts the charge current and termina-
tion voltage as described in the JEITA specification for
safe use of secondary Li+ batteries (A Guide to the Safe
Use of Secondary Lithium Ion Batteries in Notebook-type
Personal Computers, April 20, 2007). As shown in Figure
10, there are four temperature thresholds that change
the battery charger operation: T1, T2, T3, and T4. When
the thermistor input exceeds the extreme temperatures
(< T1 or > T4), the charger shuts off and all respective
charging timers are suspended. While the thermistor
remains out of range, no charging occurs, and the timer
counters hold their state. When the thermistor input
comes back into range, the charge timers continue to
count. The middle thresholds (T2 and T3) do not shut
the charger off, but adjust the current/voltage targets
to maximize charging while reducing battery stress.
Between T3 and T4, the voltage target is reduced (see
V
ever, the charge timers continue to count. Between T1
and T2, the charging current target is reduced to 50%
of its normal operating value; and similarly the charge
timers continue to count.
24
BATREG
Continuous Power
Board Parameters
Dissipation
in the Electrical Characteristics table); how-
B JC
B JA
1619mW
Derate 20.2mW/NC above
+70NC/W
49.4NC/W
9NC/W
• Still air
• 4-layer board
• 1.5oz copper on outer layers
• 1oz copper on inner layers
• 1.6mm thick board (62mil)
• 4in x 4in board
• Four center thermal vias
• FR-4
Thermistor Monitor (THM)
FOUR-LAYER PCB
(JESD51-9:2s2p)
If the thermistor functionality is not required, connect a
1MI resistor from THM to AVL and another 1MI resis-
tor from THM to GND. This biases the THM node to be
½ of the AVL voltage telling the MAX8900_ that the bat-
tery temperature is between the T2 and T3 temperature
range. Furthermore, the high 2MI impedance presents
a minimal load to AVL.
Table 2 shows that the MAX8900_ is compatible with
several standard thermistor values. When using a 10kI
thermistor with a beta of 3380K, the configuration of
Figure 11A provides for temperature trip thresholds that
are very close to the nominal T1, T2, T3, and T4 (see the
Electrical Characteristics table). When using alternate
resistance and/or beta thermistors, the circuit of Figure
11A may result in temperature trip thresholds that are dif-
ferent from the nominal values. In this case, the circuit of
Figure 11B allows for compensating the thermistor to shift
the temperature trip thresholds back to the nominal value.
In general, smaller values of R
trip thresholds down; however, the lower temperature
thresholds are affected more then the higher temperature
thresholds. Furthermore, larger values of R
the temperature trip thresholds up; however, the higher
temperature thresholds are affected more than the lower
temperature thresholds. For assistance with thermistor
calculations, use the spreadsheet at the following link:
www.maxim-ic.com/tools/other/software/MAX8900-
THERMISTOR.XLS
The general relation of thermistor resistance to tempera-
ture is defined by the following equation:
where:
R
R
+25NC.
ß = The material constant of the thermistor, which
T = The temperature of the thermistor in NC.
THRM
25
= The resistance in I of the thermistor at T
typically ranges from 3000K to 5000K.
R
= The resistance in I of the thermistor at tem-
THRM
perature T in Celsius.
=
R
25
xe

β 




T 273 C 298 C
TP
+
shift all the temperature
1
N
-
1
N



TS



shift all
A
=