参数资料
| 型号： | MAX8756ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 26/30页 |
| 文件大小： | 0K |
| 描述： | IC CNTRL DUAL PS 28-TQFN |
| 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： | 4 V ~ 26 V |
| 输出数： | 2 |
| 输出电压： | 1.5V，1.8V，1 V ~ 2.3 V |
| 工作温度： | 0°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（4x4） |
| 包装： | 带卷 (TR) |
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Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
Choose a Schottky diode (D L ) with a forward-voltage
drop low enough to prevent the low-side MOSFET’s
( Δ I UP ). This results in a minimum operating voltage
defined by the following equation:
V IN ( MIN ) = V OUT + V CHG + h ?
? 1 ? ( V OUT + V DIS )
body diode from turning on during the dead time. As a
general rule, select a diode with a DC current rating
equal to 1/3 the load current. This diode is optional and
can be removed if efficiency is not critical.
? 1
? D MAX
?
?
Boost Capacitors
The boost capacitors (C BST ) must be selected large
enough to handle the gate-charging requirements of
the high-side MOSFETs. Typically, 0.1μF ceramic
capacitors work well for low-power applications driving
medium-sized MOSFETs. However, high-current appli-
cations driving large, high-side MOSFETs require boost
capacitors larger than 0.1μF. For these applications,
select the boost capacitors to avoid discharging the
capacitor more than 200mV while charging the high-
side MOSFETs’ gates:
where V CHG and V DIS are the parasitic voltage drops in
the charge and discharge paths, respectively. A rea-
sonable minimum value for h is 1.5, while the absolute
minimum input voltage is calculated with h = 1.
Maximum Input Voltage
The MAX8716/MAX8717/MAX8756/MAX8757 controller
includes a minimum on-time specification, which deter-
mines the maximum input operating voltage that main-
tains the selected switching frequency (see the
Electrical Characteristics table). Operation above this
maximum input voltage results in pulse-skipping opera-
C BST =
Q GATE
200 mV
tion, regardless of the operating mode selected by
SKIP . At the beginning of each cycle, if the output volt-
age is still above the feedback threshold voltage, the
controller does not trigger an on-time pulse, effectively
C BST =
= 0 . 065 μ F
V IN ( SKIP ) = V OUT ? ?
where Q GATE is the total gate charge specified in the
high-side MOSFET’s data sheet. For example, assume
the FDS6612A n-channel MOSFET is used on the high
side. According to the manufacturer’s data sheet, a sin-
gle FDS6612A has a maximum gate charge of 13nC
(V GS = 5V). Using the above equation, the required
boost capacitance would be:
13 nC
100 mV
Selecting the closest standard value, this example
requires a 0.1μF ceramic capacitor.
Applications Information
Duty-Cycle Limits
Minimum Input Voltage
The minimum input operating voltage (dropout voltage)
is restricted by the maximum duty-cycle specification
(see the Electrical Characteristics table). For the best
dropout performance, use the slowest switching-fre-
quency setting (FSEL = GND). However, keep in mind
that the transient performance gets worse as the step-
down regulators approach the dropout voltage, so bulk
output capacitance must be added (see the voltage
sag and soar equations in the Design Procedure sec-
tion). The absolute point of dropout occurs when the
inductor current ramps down during the off-time
( Δ I DOWN ) as much as it ramps up during the on-time
skipping a cycle. This allows the controller to maintain
regulation above the maximum input voltage, but forces
the controller to effectively operate with a lower switch-
ing frequency. This results in an input threshold voltage
at which the controller begins to skip pulses (V IN(SKIP) ):
? 1 ?
? ? OSC t ON ( MIN ) ?
where f OSC is the switching frequency selected by FSEL.
PCB Layout Guidelines
Careful PCB layout is critical to achieving low switching
losses and clean, stable operation. The switching
power stage requires particular attention (Figure 10). If
possible, mount all the power components on the top
side of the board, with their ground terminals flush
against one another. Follow these guidelines for good
PCB layout:
? Keep the high-current paths short, especially at the
ground terminals. This practice is essential for sta-
ble, jitter-free operation.
? Keep the power traces and load connections short.
This practice is essential for high efficiency. Using
thick copper PCBs (2oz vs. 1oz) can enhance full-
load efficiency by 1% or more. Correctly routing PCB
traces is a difficult task that must be approached in
terms of fractions of centimeters, where a single m Ω
of excess trace resistance causes a measurable effi-
ciency penalty.
26
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相关代理商/技术参数 |
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|---|---|
| MAX8757ETG+ | 制造商:Maxim Integrated Products 功能描述:INTERLEAVED HI-EFF AND DUAL PS CNTRLR 24TQFN EP - Rail/Tube |
| MAX8757ETI+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX8758ETG+ | 功能描述:LCD 驱动器 Step-Up Regulator RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX8758ETG+T | 功能描述:LCD 驱动器 Step-Up Regulator RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX8758ETJ | 功能描述:LCD 驱动器 Step-Up Regulator RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
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