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参数资料
| 型号： | MAX8677CETG+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/21页 |
| 文件大小： | 0K |
| 描述： | IC USB/AC ADP CHARGER 24-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 功能： | 充电管理 |
| 电池化学： | 锂离子（Li-Ion）、锂聚合物（Li-Pol） |
| 电源电压： | 4.1 V ~ 6.6 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 供应商设备封装： | 24-TQFN-EP（4x4） |
| 包装： | 带卷 (TR) |
1.5A Dual-Input USB/AC Adapter Charger
and Smart Power Selector
R T = R 25 × e ?? β ? ? T + 273 ? 298 ? ? ??
For a typical 10kΩ (at +25°C) thermistor and a 10kΩ
R TB resistor, the charger enters a temperature suspend
state when the thermistor resistance falls below 3.97k Ω
(too hot) or rises above 28.7k Ω (too cold). This corre-
sponds to a 0°C to +50°C range when using a 10k Ω
NTC thermistor with a beta of 3500. The general rela-
tion of thermistor resistance to temperature is defined
by the following equation:
? ? 1 1 ? ?
where:
Power Dissipation
It is important to ensure that the heat generated by the
MAX8677C is dissipated into the PCB. The package’s
exposed paddle must be soldered to the PCB with mul-
tiple vias tightly packed under the exposed paddle to
ensure optimum thermal contact to the ground plane.
This minimizes heat rise in the IC and ensures that
maximum charging current is maintained over the
widest range of external conditions. Table 4 shows the
thermal characteristics of the MAX8677C package.
Table 4. Package Thermal Characteristics
R T = The resistance in Ω of the thermistor at tempe-
rature T in Celsius
SINGLE-LAYER
PCB
MULTILAYER
PCB
R 25 = The resistance in Ω of the thermistor at +25°C
β = The material constant of the thermistor, which
typically ranges from 3000K to 5000K
T = The temperature of the thermistor in °C
Table 3 shows the MAX8677C THM temperature limits
Continuous
Power
Dissipation
θ JA
θ JC
1666.7mW
Derate 20.8mW/°C
above +70°C
48°C/W
2.7°C/W
2222.2mW
Derate 27.8mW/°C
above +70°C
36°C/W
2.7°C/W
for different thermistor material constants.
Some designs might prefer other thermistor tempera-
ture limits. Threshold adjustment can be accommodat-
ed by changing R TB , connecting a resistor in series
and/or in parallel with the thermistor, or using a thermis-
tor with different β . For example, a +45°C hot threshold
and 0°C cold threshold can be realized by using a ther-
mistor with a β of 4250 and connecting 120k Ω in paral-
lel. Since the thermistor resistance near 0°C is much
higher than it is near +50°C, a large parallel resistance
lowers the cold threshold, while only slightly lowering
the hot threshold. Conversely, a small series resistance
raises the cold threshold, while only slightly raising the
hot threshold. Raising R TB lowers both the hot and cold
thresholds, while lowering R TB raises both thresholds.
PCB Layout and Routing
Good design minimizes ground bounce and voltage
gradients in the ground plane, which can result in insta-
bility or regulation errors. 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 paddle directly under the IC. Use
multiple tightly spaced vias to the ground plane under
the exposed paddle to help cool the IC. Position input
capacitors from DC, SYS, BAT, 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 BAT, as
short and wide as possible. Refer to the MAX8677C
evaluation kit for a suitable PCB layout example.
Table 3. Fault Temperatures for Different Thermistors
Thermistor β (K)
R TB (k Ω ) (Figure 7)
Resistance at +25°C (k Ω )
Resistance at +50°C (k Ω )
Resistance at 0°C (k Ω )
Nominal Hot-Trip Temperature (°C)
Nominal Cold-Trip Temperature (°C)
3000
10
10
4.59
25.14
55
-3
3250
10
10
4.30
27.15
53
-1
3500
10
10
4.03
29.32
51
0
3750
10
10
3.78
31.66
49
2
4250
10
10
3.32
36.91
46
4.5
Chip Information
PROCESS: BiCMOS
______________________________________________________________________________________
19
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