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| 型号： | MAX8971EWP+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/39页 |
| 文件大小： | 0K |
| 描述： | IC DCDC CHRGR LI+ 1CELL 20WLP |
| 标准包装： | 2,500 |
| 功能： | 充电管理，过压/欠压保护 |
| 电池化学： | 锂离子（Li-Ion）、锂聚合物（Li-Pol） |
| 电源电压： | 4 V ~ 7.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | * |
| 封装/外壳： | * |
| 供应商设备封装： | * |
| 包装： | * |
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MAX8971
Industry's Smallest 1.55A
1-Cell Li+ DC-DC Charger
Detailed Description
The MAX8971 is a JEITA-compliant Li+ switching
battery charger that safely charges a single Li+ cell
in accordance with JEITA specifications. The IC
accepts an input supply range from 4V to 7.5V, but
disables charging if the supply voltage exceeds +7.5V,
protecting against unqualified or faulty AC adapters.
The step-down converter supplies up to 1.5A to the bat-
tery. The IC includes charger features thermistor monitor,
charger status and fault outputs. Also included are interrupt
signals to the processor. Flexibility is maintained with
adjustable charge current, input current limit, and a
minimum battery voltage (when charging is scaled back
to hold the battery voltage up) through an I 2 C interface.
DC Input—Fast-Hysteretic
Step-Down Regulator
If a valid DC input is present, battery charging is
supplied by the high-frequency step-down regulator from
DC. The step-down regulation point is then controlled
by three feedback signals: maximum step-down output
current programmed by the input current limit, maxi-
mum charger current programmed for the fast-charge
current, and maximum die temperature. The feedback
signal requiring the smallest current controls the average
output current in the inductor. This scheme minimizes
total power dissipation for battery charging, and allows
the battery to absorb any load transients with minimum
voltage disturbance.
A proprietary hysteretic current PWM control scheme
ensures fast switching and physically tiny external
components. The feedback control signal that requires
the smallest input current, controls the center of the peak
and valley currents in the inductor. The ripple current
is internally set to provide 4MHz operation. When the
input voltage decreases near the output voltage, very
high duty cycle occurs. Due to minimum off-time, 4MHz
operation is not achievable. The controller then provides
minimum off-time, peak current regulation. Similarly,
when the input voltage is too high to allow 4MHz opera-
tion due to the minimum off-time, the controller becomes
a minimum on-time, valley current regulator. In this
way, ripple current in the inductor is always as small as
possible to reduce ripple voltage-on battery for a given
Maxim Integrated
capacitance. The ripple current is made to vary with
input voltage and output voltage in a way that reduces
frequency variation. However, the frequency still varies
somewhat with operating conditions.
Soft-Start
To prevent input current transients, the rate of change
of the input current (di/dt) and charge current is
limited. When the input is valid the charge current ramps
from 0mA to the fast-charge current value in 1.5ms.
Charge current also soft-starts when transitioning from
the prequalification state to the fast-charge state. There
is no di/dt limiting when transitioning from the done state
to the fast-charge state.
PVL and AVL
PVL is a 5V linear regulator that the IC uses to power the
gate drivers for its step-down charger. PVL also charges
the BST capacitor. The PVL linear regulator is on when
DC is greater than ~2.5V, otherwise it is off. Bypass PVL
with a 1 F F ceramic capacitor to PG. Powering external
loads from PVL is not recommended.
As shown in Figure 1, AVL is a filtered output from the
PVL linear regulator that the IC uses to power
its internal analog circuits. The filter consists of an
internal 10 I resistor, and the AVL external bypass
capacitor (4.7 F F). This filter creates a 100kHz lowpass fil-
ter that cleans the 4MHz switching noise from the analog
portion of the IC. Connect a 4.7 F F ceramic capacitor
from AVL to GND. Powering external loads with AVL is
not recommended.
Thermistor Input (THM)
The THM input connects to an external negative
temperature coefficient (NTC) thermistor to monitor
battery or system temperature. Charging is suspended
when the thermistor temperature is out of range. The
charge timers are 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.
Since the thermistor monitoring circuit employs an
external bias resistor from THM to AVL, the thermistor
is not limited only to 10k I (at +25 N C). Any resistance
thermistor can be used as long as the value is equivalent
to the thermistors +25 N C resistance. For example, with a
16
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8971QEWP+T | 功能描述:电池管理 Switch-Mode Li+ Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX8973AEWI+ | 制造商:Maxim Integrated Products 功能描述:HIGH CURRENT, MULTI-PHASE DC/DC STEP-DOWN CONVERTER - Rail/Tube |
| MAX8973AEWI+T | 制造商:Maxim Integrated Products 功能描述:HIGH CURRENT, MULTI-PHASE DC/DC STEP-DOWN CONVERTER - Tape and Reel |
| MAX8982AEWO+T | 制造商:Maxim Integrated Products 功能描述:POWER MANAGEMENT IC FOR ICERA E400/E450 PLATFORM-MINI CARD - Tape and Reel |
| MAX8982EWO+T | 功能描述:PMIC 解决方案 PMIC for ICERA E400/E450 Platform RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
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