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| 型号： | MAX1980ETP+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 24/33页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 20-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 系列： | Quick-PWM™ |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 50% |
| 电源电压： | 4.5 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 20-WQFN 裸露焊盘 |
| 包装： | 管件 |
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Quick-PWM Slave Controller with
Driver Disable for Multiphase DC-DC Converter
Switching ) = ( V IN ( MAX ) ) 2 C RSS f SW I LOAD
I GATE η
? V IN
? ? SW switching-loss equation. If the high-side
If the master/slave converter is operated as the second
stage of a two-stage power-conversion system, tanta-
lum input capacitors are acceptable. In either configu-
ration, choose an input capacitor that exhibits less than
+10 ° C temperature rise at the RMS input current for
optimal circuit longevity.
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-cur-
rent 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 .
Conversely, if the losses at V IN(MAX) are significantly
higher than the losses at V IN(MIN) , consider reducing
the size of N H . If V IN does not vary over a wide range,
the minimum power dissipation occurs where the resis-
tive losses equal the switching losses.
Choose a low-side MOSFET that has the lowest possi-
ble on-resistance (R DS(ON) ), comes in a moderate-
sized package (i.e., one or two SO-8s, DPAK or
D 2 PAK), and is reasonably priced. Make sure that the
Calculating the power dissipation of 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 volt-
age, source inductance, and PC board layout charac-
teristics. 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
where C RSS is the reverse transfer capacitance of N H
and I GATE is the peak gate-drive source/sink current
(1A typ).
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
2
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:
? ? ? I
?
? V
?
? 1 ? ? ? ? LOAD ? R DS ( ON )
?
? V IN ( MAX ) ? ? ? ?
? ?
DL gate driver can supply sufficient current to support
the gate charge and the current injected into the para-
sitic gate-to-drain capacitor caused by the high-side
MOSFET turning on; otherwise, cross-conduction prob-
PD ( N L Re sistive ) =
OUT
η ?
2
? V
? ? I
?
PD ( N H Re sistive ) = ? OUT ? ? LOAD ? R DS ( ON )
I LOAD VALLEY ( MAX ) + ?
? I LOAD ( MAX ) LIR ?
?
lems may occur.
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:
2
? V IN ? ? η ?
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 don ’ t usually become an issue
until the input is greater than approximately 15V.
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 protect against this
possibility, “ overdesign ” the circuit to tolerate:
= η I
? 2 ?
where I VALLEY(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 (D1) with a forward voltage low
enough to prevent the low-side MOSFET 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 η ) of
the load current. This diode is optional and can be
removed if efficiency is not critical.
24
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1980ETP+ | 功能描述:DC/DC 开关控制器 PWM Slave Controller w/Driver Disable RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1980ETP+T | 功能描述:DC/DC 开关控制器 PWM Slave Controller w/Driver Disable RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1980ETP+TG075 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1980ETP-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1980ETP-TG075 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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