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| 型号： | MAX17480EVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 41/48页 |
| 文件大小： | 0K |
| 描述： | EVALUATION KIT FOR MAX17480 |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 3，非隔离 |
| 输入电压： | 4 ~ 26 V |
| 稳压器拓扑结构： | 降压 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX17480 |
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AMD 2-/3-Output Mobile Serial
VID Controller
(
) 2 ? ? C I RSS f SW ? ? I LOAD
? ?
PD (N H Switching) = V IN ( MAX )
? ? V ? ? ? I ? 2
PD (N L Resistive) = ? 1 ? ?? ? ? ? LOAD ? R DS ( ON )
?
PD (N H Resistive) = ? OUT ? I LOAD DS ( O N )
= I PEAK ( MAX ) ? ??
??
?
?
Core 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-
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(MIN) and V IN(MAX) . Calculate both of these sums.
Ideally, the losses at V IN(MIN) should be roughly equal to
losses at V IN(MAX) , with lower losses in between. If the
losses at V IN(MIN) are significantly higher than the losses
at V IN(MAX) , consider increasing the size of N H (reducing
R DS(ON) but with higher C GATE ). Conversely, if the loss-
es at V IN(MAX) are significantly higher than the losses at
V IN(MIN) , consider reducing the size of N H (increasing
R DS(ON) to lower C GATE ). If V IN does not vary over a
wide range, the minimum power dissipation occurs
where the resistive losses equal the switching losses.
Choose a low-side MOSFET that has the lowest possible
on-resistance (R DS(ON) ), comes in a moderate-sized
package (i.e., one or two 8-pin SOs, DPAK, or D2PAK),
and is reasonably priced. Make sure that the DL gate dri-
ver can supply sufficient current to support the gate
charge and the current injected into the parasitic gate-to-
drain capacitor caused by the high-side MOSFET turning
on; otherwise, cross-conduction problems might occur
(see the Core SMPS MOSFET Gate Drivers section).
Core MOSFET Power 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 the
minimum input voltage:
? V ? 2
R
? V IN ?
where I LOAD is the per-phase current.
Generally, a small high-side MOSFET is desired to
reduce switching losses at high input voltages.
However, the R DS(ON) required to stay within package
power dissipation often limits how small the MOSFET
can be. Again, the optimum occurs when the switching
losses equal the conduction (R DS(ON) ) losses. High-
side switching losses do not usually become an issue
until the input is greater than approximately 15V.
Calculating the power dissipation in the high-side
MOSFET (N H ) due to switching losses is difficult since it
must allow for difficult quantifying factors that influence
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 substitute for breadboard
evaluation, preferably including verification using a
thermocouple mounted on N H :
:
GAT E
where C RSS is the reverse transfer capacitance of N H ,
I GATE is the peak gate-drive source/sink current (1A,
typ), and I LOAD is the per-phase current.
Switching losses in the high-side MOSFET can become
an insidious heat problem when maximum AC adapter
voltages are applied, due to the squared term in the C
x V IN 2 x f SW switching-loss equation. If the high-side
MOSFET chosen for adequate R DS(ON) at low battery
voltages becomes extraordinarily hot when biased from
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 input voltage:
OUT
? ?
? ? V IN ( MAX ) ? ? ? η TOTAL ?
The worst case for MOSFET power dissipation occurs
under heavy overloads that are greater than
I LOAD(MAX) , but are not quite high enough to exceed
the current limit and cause the fault latch to trip. To pro-
tect against this possibility, the circuit can be “overde-
signed” to tolerate:
? I INDUCTOR ? I LOAD ( MAX ) LIR ?
I LOAD ( MAX ) = I PEAK ( MAX ) ?
2 2
where I PEAK(MAX) is the maximum valley current
allowed by the current-limit circuit, including threshold
tolerance and on-resistance variation. The MOSFETs
must have a good-sized heatsink to handle the over-
load power dissipation.
Choose a Schottky diode (D L ) with a forward voltage
low enough to prevent the low-side MOSFET body
diode from turning on during the dead time. As a gen-
eral rule, select a diode with a DC current rating equal
to 1/3 the load current per phase. This diode is optional
and can be removed if efficiency is not critical.
Core 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,
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX17480EVKIT+ | 功能描述:电源管理IC开发工具 MAX17480 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX17480GTL+ | 功能描述:显示驱动器和控制器 2-/3-Output Mobile erial VID Ctlr RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX17480GTL+T | 功能描述:显示驱动器和控制器 2-/3-Output Mobile erial VID Ctlr RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX17482GTL+ | 功能描述:电压模式 PWM 控制器 NDA IC RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX17482GTL+T | 功能描述:电压模式 PWM 控制器 NDA IC RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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