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| 型号： | MAX8745ETJ+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/36页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PWR SUP QUAD 32TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 6 V ~ 26 V |
| 输出数： | 4 |
| 输出电压： | 3.3V，5V，1 V ~ 26 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
Table 2. Component Suppliers
The MAX8744/MAX8745 switch-mode power supplies
(SMPS) require a 5V bias supply in addition to the high-
SUPPLIER
AVX
Central Semiconductor
Fairchild
International Rectifier
KEMET
NEC/Tokin
Panasonic
Philips
Pulse
Renesas
SANYO
Sumida
Taiyo Yuden
TDK
TOKO
Vishay (Dale, Siliconix)
WEBSITE
www.avx.com
www.centralsemi.com
www.fairchildsemi.com
www.irf.com
www.kemet.com
www.nec-tokin.com
www.panasonic.com/industrial
www.philips.com
www.pulseeng.com
www.renesas.com
www.edc.sanyo.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.tokoam.com
www.vishay.com
power input supply (battery or AC adapter). This 5V bias
supply is generated by the controller’s internal 5V linear
regulator (LDO5). This bootstrapped LDO allows the
controller to power up independently. The gate-driver
input supply is connected to the fixed 5V linear-regulator
output (LDO5). Therefore, the 5V LDO supply must pro-
vide LDO5 (PWM controller) and the gate-drive power,
so the maximum supply current required is:
I BIAS = I CC + f SW (Q G(LOW) + Q G(HIGH) )
= 5mA to 50mA (typ)
where I CC is 0.7mA (typ), f SW is the switching frequency,
and Q G(LOW) and Q G(HIGH) are the MOSFET data
sheet’s total gate-charge specification limits at V GS = 5V.
SMPS to LDO Bootstrap Switchover
When the 5V main output voltage is above the LDO5
bootstrap-switchover threshold and has completed
soft-start, an internal 1 Ω (typ) p-channel MOSFET
shorts CSL5 to LDO5, while simultaneously shutting
down the LDO5 linear regulator. This bootstraps the
device, powering the internal circuitry and external
Detailed Description
The MAX8744/MAX8745 standard application circuit
(Figure 1) generates the 5V/5A and 3.3V/5A typical of the
main supplies in a notebook computer. The input supply
range is 7V to 24V. See Table 1 for component selec-
tions, while Table 2 lists the component manufacturers.
The MAX8744/MAX8745 contain two interleaved, fixed-
frequency, step-down controllers designed for low-volt-
age power supplies. The optimal interleaved architecture
guarantees out-of-phase operation, reducing the input
capacitor ripple. One internal LDO generates the keep-
alive 5V power. The MAX8744/MAX8745 have an auxil-
iary LDO with an adjustable output for generating either
the 3.3V keep-alive supply or regulating the low-power
12V system supply.
Fixed 5V Linear Regulator (LDO5)
An internal linear regulator produces a preset 5V low-
current output. LDO5 powers the gate drivers for the
external MOSFETs, and provides the bias supply
required for the SMPS analog controller, reference, and
logic blocks. LDO5 supplies at least 100mA for exter-
nal and internal loads, including the MOSFET gate
drive, which typically varies from 5mA to 50mA,
depending on the switching frequency and external
MOSFETs selected. Bypass LDO5 with a 4.7μF or
greater ceramic capacitor (1μF per 25mA of load) to
guarantee stability under the full-load conditions.
loads from the 5V SMPS output (CSL5), rather than
through the linear regulator from the battery. Boot-
strapping reduces power dissipation due to gate
charge and quiescent losses by providing power from
a 90%-efficient switch-mode source, rather than from a
much-less-efficient linear regulator. The current capa-
bility increases from 100mA to 200mA when the LDO5
output is switched over to CSL5. When ON5 is pulled
low, the controller immediately disables the bootstrap
switch and reenables the 5V LDO.
Reference (REF)
The 2V reference is accurate to ±1% over temperature
and load, making REF useful as a precision system ref-
erence. Bypass REF to GND with a 0.1μF or greater
ceramic capacitor. The reference sources up to 50μA
and sinks 5μA to support external loads. If highly accu-
rate specifications are required for the main SMPS out-
put voltages, the reference should not be loaded.
Loading the reference reduces the LDO5, CSL5
(OUT5), CSL3 (OUT3), and OUTA output voltages
slightly because of the reference load-regulation error.
System Enable/Shutdown ( SHDN )
Drive SHDN below the precise SHDN input falling-edge
trip level to place the MAX8744/MAX8745 in its low-
power shutdown state. The controller consumes only
8μA of quiescent current while in shutdown mode.
When shutdown mode activates, the reference turns off
after the controller completes the shutdown sequence
______________________________________________________________________________________
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX874C/D | 功能描述:基准电压& 基准电流 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 |
| MAX874CPA | 功能描述:基准电压& 基准电流 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 |
| MAX874CPA+ | 功能描述:基准电压& 基准电流 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 |
| MAX874CSA | 功能描述:基准电压& 基准电流 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 |
| MAX874CSA+ | 功能描述:基准电压& 基准电流 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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