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参数资料
| 型号： | MAX745EAP+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/8页 |
| 文件大小： | 0K |
| 描述： | IC BATTERY CHARGER LI+ 20-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 功能： | 充电管理 |
| 电池化学： | 锂离子（Li-Ion） |
| 电源电压： | 6 V ~ 24 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 20-SSOP |
| 包装： | 带卷 (TR) |
Switch-Mode Lithium-Ion
Battery Charger
MOSFET Drivers
The MAX745 drives external N-channel MOSFETs to
switch the input source generating the battery voltage or
current. Since the high-side N-channel MOSFET’s gate
must be driven to a voltage higher than the input source
voltage, a charge pump is used to generate such a volt-
age. The capacitor (C7) charges through D2 to approxi-
mately 5V when the synchronous rectifier (M1B) turns on
(Figure 1). Since one side of C7 is connected to LX (the
source of M1A), the high-side driver (DHI) drives the gate
up to the voltage at BST, which is greater than the input
voltage while the high-side MOSFET is on.
The synchronous rectifier (M1B) behaves like a diode
but has a smaller voltage drop, improving efficiency. A
small dead time is added between the time when the
high-side MOSFET is turned off and when the synchro-
nous rectifier is turned on, and vice versa. This
prevents crowbar currents during switching transitions.
Place a Schottky rectifier from LX to ground (D1, across
M1B’s drain and source) to prevent the synchronous
rectifier’s body diode from conducting during the dead
time. The body diode typically has slower switching-
recovery times, so allowing it to conduct degrades
efficiency. D1 can be omitted if efficiency is not a
concern, but the resulting increased power dissipation
in the synchronous rectifier must be considered.
Since the BST capacitor is charged while the synchro-
nous rectifier is on, the synchronous rectifier may not be
replaced by a rectifier. The BST capacitor will not fully
charge without the synchronous rectifier, leaving the high-
Minimum Input Voltage
The input voltage to the charger circuit must be greater
than the maximum battery voltage by approximately 2V
so the charger can regulate the voltage properly. The
input voltage can have a large AC-ripple component
when operating from a wall cube. The voltage at the low
point of the ripple waveform must still be approximately
2V greater than the maximum battery voltage.
Using components as indicated in Figure 1, the minimum
input voltage can be determined by the following formula:
[ V BATT + V D6 + I CHG (R DS(ON) + R L + R1)]
V IN x
0.89
where: V IN is the input voltage;
V D6 is the voltage drop across D6
(typically 0.4V to 0.5V);
I CHG is the charging current;
R DS(ON) is the high-side
MOSFET M1A’s on-resistance;
R L is the the inductor’s series resistance;
R1 is the current-sense resistor R1’s value.
__________________Pin Configuration
TOP VIEW
side MOSFET with insufficient gate drive to turn on.
However, the synchronous rectifier can be replaced with
a small MOSFET (such as a 2N7002) to guarantee that
the BST capacitor is allowed to charge. In this case, the
majority of the high charging currents are carried by D1,
IBAT 1
DCIN 2
VL 3
CCV 4
20 BST
19 LX
18 DHI
17 DLO
and not by the synchronous rectifier.
Internal Regulator and Reference
The MAX745 uses an internal low-dropout linear regula-
tor to create a 5.4V power supply (VL), which powers its
internal circuitry. The VL regulator can supply up to
25mA. Since 4mA of this current powers the internal cir-
cuitry, the remaining 21mA can be used for external cir-
cuitry. MOSFET gate-drive current comes from VL,
which must be considered when drawing current for
other functions. To estimate the current required to drive
CCI 5
THM/SHDN 6
REF 7
VADJ 8
SETI 9
GND 10
MAX745
SSOP
16 PGND
15 CS
14 BATT
13 STATUS
12 CELL0
11 CELL1
the MOSFETs, multiply the sum of the MOSFET gate
charges by the switching frequency (typically 300kHz).
Bypass VL with a 4.7 μ F capacitor to ensure stability.
The MAX745 internal 4.2V reference voltage must be
bypassed with a 0.1 μ F or greater capacitor.
___________________Chip Information
TRANSISTOR COUNT: 1695
SUBSTRATE CONNECTED TO GND
8
_______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX745EVKIT | 功能描述:电池管理 Evaluation Kit for the MAX745 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 |
| MAX7461EUK | 制造商:Maxim Integrated Products 功能描述:LOSS-OF-SYNC ALARM - Rail/Tube |
| MAX7461EUK+ | 制造商:Maxim Integrated Products 功能描述:LOSS OF SYNC ALARM 5PIN SOT-23 - Rail/Tube |
| MAX7461EUK+T | 功能描述:视频 IC Loss-Of-Sync Alarm RoHS:否 制造商:Fairchild Semiconductor 工作电源电压:5 V 电源电流:80 mA 最大工作温度:+ 85 C 封装 / 箱体:TSSOP-28 封装:Reel |
| MAX7461EUK-T | 功能描述:视频 IC RoHS:否 制造商:Fairchild Semiconductor 工作电源电压:5 V 电源电流:80 mA 最大工作温度:+ 85 C 封装 / 箱体:TSSOP-28 封装:Reel |
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