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| 型号： | MAX8765ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 26/30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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MAX1908/MAX8724/MAX8765/MAX8765A
Low-Cost Multichemistry Battery Chargers
Choose crossover frequency f CO_CS to be 1/5th the
MAX1908/MAX8724/MAX8765/MAX8765A switching
frequency:
where:
t OFF = 2.5μs × (V DCIN – V BATT )/V DCIN
V BATT < 0.88 × V DCIN
f CO _ CS =
GMS
2 π C CS
= 80 kHz
or:
t OFF = 0.3μs
f CO _ CS =
= 16 kHz
Solving for C CS , C CS = 2nF.
To be conservative, set C CS = 10nF, which sets the
crossover frequency at:
GMS
2 π 10 nF
The compensation pole, f P_CS is set at:
V BATT > 0.88 × V DCIN
Figure 11 illustrates the variation of ripple current vs.
battery voltage when charging at 3A with a fixed 19V
input voltage.
Higher inductor values decrease the ripple current.
Smaller inductor values require higher saturation cur-
rent capabilities and degrade efficiency. Designs for
ripple current, I RIPPLE = 0.3 × I CHG usually result in a
good balance between inductor size and efficiency.
f P _ CS =
1
2 π R OGMS × C CS
= 0 . 0016 Hz
Input Capacitor
Input capacitor C1 must be able to handle the input
ripple current. At high charging currents, the DC-DC
Component Selection
Table 3 lists the recommended components and refers
to the circuit of Figure 2. The following sections
describe how to select these components.
Inductor Selection
Inductor L1 provides power to the battery while it is
being charged. It must have a saturation current of at
least the charge current (I CHG ), plus 1/2 the current rip-
ple I RIPPLE :
I SAT = I CHG + (1/2) I RIPPLE
Ripple current varies according to the equation:
I RIPPLE = (V BATT ) × t OFF /L
converter operates in continuous conduction. In this
case, the ripple current of the input capacitor can be
approximated by the following equation:
I C 1 = I CHG D ? D 2
where:
I C1 = input capacitor ripple current.
D = DC-DC converter duty ratio.
I CHG = battery-charging current.
Input capacitor C1 must be sized to handle the maxi-
mum ripple current that occurs during continuous con-
duction. The maximum input ripple current occurs at
1.5
1.0
RIPPLE CURRENT vs.
BATTERY VOLTAGE
3 CELLS
4 CELLS
50% duty cycle; thus, the worst-case input ripple cur-
rent is 0.5 × I CHG . If the input-to-output voltage ratio is
such that the DC-DC converter does not operate at a
50% duty cycle, then the worst-case capacitor current
occurs where the duty cycle is nearest 50%.
The input capacitor ESR times the input ripple current
sets the ripple voltage at the input, and should not
exceed 0.5V ripple. Choose the ESR of C1 according to:
0.5
V DCIN = 19V
ESR C 1 <
0.5 V
I C 1
0
VCTL = ICTL = LDO
The input capacitor size should allow minimal output
voltage sag at the highest switching frequency:
8
9
10 11 12 13 14 15 16 17 18
V BATT (V)
Figure 11. Ripple Current vs. Battery Voltage
26
I C1
2
= C 1
dV
dt
Maxim Integrated
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| MAX876ACPA+ | 功能描述:基准电压& 基准电流 10V Precision Voltage Reference RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel |
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