参数资料
| 型号： | MAX8756ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/30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
shows the input-capacitor RMS current vs. input volt-
age for an application that requires 5V/5A and 3.3V/5A.
This shows the improvement of the 40/60 optimal inter-
leaving over 50/50 interleaving and in-phase operation.
For most applications, nontantalum chemistries (ceramic,
aluminum, or OS-CON) are preferred due to their resis-
tance to power-up surge currents typical of systems
with a mechanical switch or connector in series with the
input. Choose a capacitor that has less than 10°C tem-
perature rise at the RMS input current for optimal relia-
bility and lifetime.
Power MOSFET Selection
Most of the following MOSFET guidelines focus on the
challenge of obtaining high load-current capability
when using high-voltage (> 20V) AC adapters. Low-
The optimum occurs when the switching losses equal
the conduction (R DS(ON) ) losses. High-side switching
losses do not become an issue until the input is greater
than approximately 15V.
Calculating the power dissipation in high-side
MOSFETs (N H ) due to switching losses is difficult, since
it must allow for difficult-to-quantify factors that influ-
ence the turn-on and turn-off times. These factors
include the internal gate resistance, gate charge,
threshold voltage, source inductance, and PCB layout
characteristics. The following switching-loss calculation
provides only a very rough estimate and is no substi-
tute for breadboard evaluation, preferably including
verification using a thermocouple mounted on N H :
PD (N H SWITCHING) =
? ? ? I ? +
current applications usually require less attention.
The high-side MOSFET (N H ) must be able to dissipate
the resistive losses plus the switching losses at both
? V IN(MAX) I LOAD f SW ? ? Q G(SW) ?
? η TOTAL ? ? GATE ?
C OSS V IN2 f SW
2
PD ( N L RESISTIVE ) = ? 1 ? ? ? ? ( I LOAD ) R DS ( ON )
? V IN ( MAX ) ? ? ?
?
) 2 R
PD ( N H RESISTIVE ) = OUT ( I LOAD DS ( ON )
I LOAD = I LIMIT ? ?
? Δ I INDUCTOR ?
?
?
?
V IN(MIN) and V IN(MAX) . Ideally, the losses at V IN(MIN)
should be roughly equal to the losses at V IN(MAX) , with
lower losses in between. If the losses at V IN(MIN) are
significantly higher, consider increasing the size of N H .
Conversely, if the losses at V IN(MAX) are significantly
higher, consider reducing the size of N H . If V IN does
not vary over a wide range, optimum efficiency is
achieved by selecting a high-side MOSFET (N H ) that
has conduction losses equal to the switching losses.
Choose a low-side MOSFET (N L ) that has the lowest
possible on-resistance (R DS(ON) ), comes in a moder-
ate-sized package (i.e., 8-pin SO, DPAK, or D 2 PAK),
and is reasonably priced. Ensure that the
MAX8716/MAX8717/MAX8756/MAX8757 DL_ gate dri-
ver can supply sufficient current to support the gate
charge and the current injected into the parasitic drain-
to-gate capacitor caused by the high-side MOSFET
turning on; otherwise, cross-conduction problems may
occur. Switching losses are not an issue for the low-
side MOSFET since it is a zero-voltage switched device
when used in the step-down topology.
Power MOSFET Dissipation
Worst-case conduction losses occur at the duty-factor
extremes. For the high-side MOSFET (N H ), the worst-
case power dissipation due to resistance occurs at
minimum input voltage:
V
V IN
Generally, use a small high-side MOSFET to reduce
switching losses at high input voltages. However, the
R DS(ON) required to stay within package power-dissi-
pation limits often limits how small the MOSFET can be.
where C OSS is the N H , MOSFET's output capacitance,
Q G(SW) 2 , is the change needed to turn on the
N H MOSFET, and I GATE is the peak gate-drive
source/sink current (1A typ).
Switching losses in the high-side MOSFET can become
a heat problem when maximum AC adapter voltages
are applied, due to the squared term in the switching-
loss equation (C x V IN 2 x f SW ). If the high-side MOSFET
chosen for adequate R DS(ON) at low battery voltages
becomes extraordinarily hot when subjected to
V IN(MAX) , consider choosing another MOSFET with
lower parasitic capacitance.
For the low-side MOSFET (N L ), the worst-case power
dissipation always occurs at maximum battery voltage:
? ? V ? ?
OUT 2
?
The absolute worst case for MOSFET power dissipation
occurs under heavy-overload conditions that are
greater than I LOAD(MAX) but are not high enough to
exceed the current limit and cause the fault latch to trip.
To protect against this possibility, “overdesign” the cir-
cuit to tolerate:
2
where I LIMIT is the peak current allowed by the current-
limit circuit, including threshold tolerance and sense-
resistance variation. The MOSFETs must have a
relatively large heatsink to handle the overload power
dissipation.
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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