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| 型号： | MAX8765ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/30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
In normal operation, the controller starts a new cycle by
turning on the high-side n-channel MOSFET and
turning off the low-side n-channel MOSFET. When the
charge current is greater than the control point (LVC),
CCMP goes high and the off-time is started. The
Discontinuous Conduction
The MAX1908/MAX8724/MAX8765/MAX8765A enter dis-
continuous-conduction mode when the output of the LVC
control point falls below 0.15V. For RS2 = 0.015 ? , this
corresponds to 0.5A:
off-time turns off the high-side n-channel MOSFET and
turns on the low-side n-channel MOSFET. The opera-
tional frequency is governed by the off-time and is
dependent upon V DCIN and V BATT . The off-time is set
by the following equations:
IMIN =
for RS2 = 0.015 ? .
0 . 15 V
20 × RS 2
= 0 . 5 A
t OFF = 2 . 5 μ s × DCIN BATT
V ? V
V DCIN
In discontinuous mode, a new cycle is not started until
the LVC voltage rises above 0.15V. Discontinuous-
mode operation can occur during conditioning charge
of overdischarged battery packs, when the charge cur-
t ON =
L × I RIPPLE
V CSSN ? V BATT
rent has been reduced sufficiently by the CCS control
loop, or when the battery pack is near full charge (con-
stant-voltage-charging mode).
I RIPPLE = BATT OFF
where:
V × t
L
MOSFET Drivers
The low-side driver output DLO switches between
PGND and DLOV. DLOV is usually connected through
a filter to LDO. The high-side driver output DHI is boot-
strapped off LX and switches between V LX and V BST .
When the low-side driver turns on, BST rises to one
f =
1
t ON + t OFF
diode voltage below DLOV.
Filter DLOV with a lowpass filter whose cutoff frequency
is approximately 5kHz (Figure 1):
These equations result in fixed-frequency operation
over the most common operating conditions.
At the end of the fixed off-time, another cycle begins if
f C =
1
2 π RC
=
1
2 π × 33 ? × 1 μ F
= 4 . 8 kHz
f =
L × I RIPPLE
( V CSSN BATT )
the control point (LVC) is greater than 0.15V, IMIN =
high, and the peak charge current is less than 6A (RS2
= 0.015 ? ), IMAX = high. If the charge current exceeds
IMAX, the on-time is terminated by the IMAX compara-
tor. IMAX governs the maximum cycle-by-cycle current
limit and is internally set to 6A (RS2 = 0.015 ? ). IMAX
protects against sudden overcurrent faults.
If, during the off-time, the inductor current goes to zero,
ZCMP = high, both the high- and low-side MOSFETs
are turned off until another cycle is ready to begin.
There is a minimum 0.3μs off-time when the (V DCIN -
V BATT ) differential becomes too small. If V BATT ≥ 0.88 ×
V DCIN , then the threshold for minimum off-time is
reached and the t OFF is fixed at 0.3μs. A maximum on-
time of 5ms allows the controller to achieve > 99% duty
cycle in continuous-conduction mode. The switching
frequency in this mode varies according to the equation:
1
+ 0 . 3 μ s
? V
Maxim Integrated
Dropout Operation
The MAX1908/MAX8724/MAX8765/MAX8765A have 99%
duty-cycle capability with a 5ms (max) on-time and 0.3μs
(min) off-time. This allows the charger to achieve dropout
performance limited only by resistive losses in the DC-DC
converter components (D1, N1, RS1, and RS2, Figure 1).
Replacing diode D1 with a p-channel MOSFET driven by
ACOK improves dropout performance (Figure 2). The
dropout voltage is set by the difference between DCIN
and CSIN. When the dropout voltage falls below 100mV,
the charger is disabled; 200mV hysteresis ensures that
the charger does not turn back on until the dropout volt-
age rises to 300mV.
Compensation
Each of the three regulation loops—input current limit,
charging current limit, and charging voltage limit—are
compensated separately using CCS, CCI, and CCV,
respectively.
21
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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 |
| 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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