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| 型号： | MAX1980ETP+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 23/33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
For in-phase operation, the maximum ESR to meet rip-
ple requirements is:
Unstable operation manifests itself in two related but
distinctly different ways: double-pulsing and feedback
loop instability. Double-pulsing occurs due to noise on
? ( V IN ? V OUT )
R ESR ≤
V RIPPLE
I LOAD ( MAX ) LIR
=
V RIPPLE
? η ? ? V OUT ?
? ? ?
? f SW L ? ? V IN ?
the output or because the ESR is so low that there isn ’ t
enough voltage ramp in the output voltage signal. This
“ fools ” the error comparator into triggering a new cycle
immediately after the minimum off-time period has
f ESR ≤ SW
where f ESR =
? V V ? V
OUT ( IN OUT )
? I
?
I RMS = ? LOAD ? ?
?
?
? V V ? V
OUT IN OUT )
(
I RMS = I LOAD ? ?
?
?
The actual capacitance value required relates to the
physical size needed to achieve low ESR, as well as to
the chemistry of the capacitor technology. Thus, the
capacitor is usually selected by ESR and voltage rating
rather than by capacitance value (this is true of tanta-
lums, OS-CONs, and other electrolytics).
When using low-capacity filter capacitors such as
ceramic or polymer types, capacitor size is usually
determined by the capacity needed to prevent V SAG
and V SOAR from causing problems during load tran-
sients. Generally, once enough capacitance is added to
meet the overshoot requirement, undershoot at the ris-
ing load edge is no longer a problem (see the V SAG and
V SOAR equations in the Transient Response section).
Output Capacitor Stability Considerations
For Quick-PWM controllers, stability is determined by
the value of the ESR zero relative to the switching fre-
quency. The boundary of instability is given by the fol-
lowing equation:
f
π
1
2 π R ESR C OUT
For a standard 300kHz application, the ESR zero fre-
quency must be well below 95kHz, preferably below
50kHz. Tantalum, Sanyo POSCAP, and Panasonic SP
capacitors in wide-spread use at the time of publication
have typical ESR zero frequencies below 30kHz. In the
standard application used for inductor selection, the
ESR needed to support a 30mV P-P ripple is 30mV/(40A
x 0.3) = 2.5m ? . Eight 270μF/2.0V Panasonic SP capac-
itors in parallel provide 1.9m ? (max) ESR. Their typical
combined ESR results in a zero at 39kHz.
Do not put high-value ceramic capacitors directly
across the output without taking precautions to ensure
stability. Ceramic capacitors have a high ESR zero fre-
quency and may cause erratic, unstable operation.
However, it ’ s easy to add enough series resistance by
placing the capacitors a couple of centimeters down-
stream from the junction of the inductor and FB pin.
expired. Double-pulsing is more annoying than harmful,
resulting in nothing worse than increased output ripple.
However, it can indicate the possible presence of loop
instability due to insufficient ESR. Loop instability can
result in oscillations at the output after line or load
steps. Such perturbations are usually damped, but can
cause the output voltage to rise above or fall below the
tolerance limits.
The easiest method for checking stability is to apply a
very fast zero-to-max load transient and carefully
observe the output voltage ripple envelope for over-
shoot and ringing. It can help to simultaneously monitor
the switching waveforms (V LX and/or I INDUCTOR ). Don ’ t
allow more than one cycle of ringing after the initial
step-response under/overshoot.
Input Capacitor Selection
The input capacitor must meet the ripple current require-
ment (I RMS ) imposed by the switching currents. The
MAX1980 multiphase slave controllers operate out-of-
phase (POL = V CC or float), staggering the turn-on times
of each phase. This minimizes the input ripple current by
dividing the load current among independent phases:
?
?
? η ? ? V IN ?
for out-of-phase operation.
When operating the MAX1980 in-phase (POL = GND),
the high-side MOSFETs turn on simultaneously, so
input capacitors must support the combined input rip-
ple currents of each phase:
?
? V IN ?
for in-phase operation.
For most applications, nontantalum chemistries (ceramic,
aluminum, or OS-CON) are preferred because of their
resilience to inrush surge currents typical of systems with
a mechanical switch or connector in series with the input.
______________________________________________________________________________________
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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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