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| 型号： | MAX1909ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 28/30页 |
| 文件大小： | 0K |
| 描述： | IC CHARGER BATTERY 28-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： | 多化学 |
| 电源电压： | 8 V ~ 28 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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Multichemistry Battery Chargers with Automatic
System Power Selector
??
I RMS = I CHG ?
?
?
?
The ripple current is determined by:
Δ IL = V BATT t OFF / L
where:
t OFF = 2.5μs (V DCIN - V BATT ) / V DCIN for
V BATT < 0.88 V DCIN
or:
t OFF = 0.3μs for V BATT > 0.88 V DCIN
Figure 11 illustrates the variation of the ripple current
vs. battery voltage when the circuit is charging at 3A
with a fixed input voltage of 19V.
Higher inductor values decrease the ripple current.
Smaller inductor values require high-saturation current
capabilities and degrade efficiency. Designs that set
LIR = Δ IL / I CHG = 0.3 usually result in a good balance
between inductor size and efficiency.
Input-Capacitor Selection
The input capacitor must meet the ripple current
requirement (I RMS ) imposed by the switching currents.
Nontantalum chemistries (ceramic, aluminum, or OS-
CON) are preferred due to their resilience to power-up
surge currents.
? V BATT ( V DCIN ? V BATT ) ?
V DCIN
The input capacitors should be sized so that the
temperature rise due to ripple current in continuous
conduction does not exceed approximately 10°C. The
maximum ripple current occurs at 50% duty factor or
V DCIN = 2 ? V BATT , which equates to 0.5 ? I CHG . If the
application of interest does not achieve the maximum
value, size the input capacitors according to the
worst-case conditions.
Output-Capacitor Selection
The output capacitor absorbs the inductor ripple cur-
rent and must tolerate the surge current delivered from
the battery when it is initially plugged into the charger.
As such, both capacitance and ESR are important
parameters in specifying the output capacitor as a filter
and to ensure the stability of the DC-DC converter (see
the Compensation section). Beyond the stability
requirements, it is often sufficient to make sure that the
output capacitor’s ESR is much lower than the battery’s
ESR. Either tantalum or ceramic capacitors can be
used on the output. Ceramic devices are preferable
because of their good voltage ratings and resilience to
surge currents.
Applications Information
Startup Conditioning Charge for
Overdischarged Cells
It is desirable to charge deeply discharged Li+ batter-
ies at a low rate to improve cycle life. The
MAX1909/MAX8725 automatically reduces the charge
current when the voltage per cell is below 3.1V. The
charge current-sense voltage is set to 4.5mV (I CHG =
300mA with RS2 = 15m Ω ) until the battery voltage rises
above the threshold. There is approximately 300mV for
3 cell, 400mV for 4 cell of hysteresis to prevent the
charge-current magnitude from chattering between the
two values.
For the MAX8725, control the ICTL voltage to set a con-
ditioning charge rate.
Layout and Bypassing
Bypass DCIN with a 1μF capacitor to ground (Figure 1).
D4 protects the MAX1909/MAX8725 when the DC
power source input is reversed. A signal diode for D4 is
adequate because DCIN only powers the LDO and the
internal reference. Bypass LDO, DHIV, DLOV, and
other pins as shown in Figure 1.
Good PC board layout is required to achieve specified
noise, efficiency, and stable performance. The PC
board layout artist must be given explicit instructions—
preferably, a sketch showing the placement of the
power-switching components and high-current routing.
Refer to the PC board layout in the MAX1909/MAX8725
evaluation kit for examples. A ground plane is essential
for optimum performance. In most applications, the cir-
cuit is located on a multilayer board, and full use of the
four or more copper layers is recommended. Use the
top layer for high-current connections, the bottom layer
for quiet connections, and the inner layers for an unin-
terrupted ground plane.
Use the following step-by-step guide:
1) Place the high-power connections first, with their
grounds adjacent:
a) Minimize the current-sense resistor trace
lengths, and ensure accurate current sensing
with Kelvin connections.
b) Minimize ground trace lengths in the high-current
paths.
c) Minimize other trace lengths in the high-current
paths.
d) Use >5mm wide traces.
28
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| MAX190ACWG | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX190ACWG+ | 功能描述:模数转换器 - ADC 12Bit 75ksps 5V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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