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| 型号： | MAX17410GTM+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 41/45页 |
| 文件大小： | 0K |
| 描述： | IC CTLR QPWM 2PH FOR IMV 48TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 系列： | * |
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Dual-Phase, Quick-PWM Controller
for IMVP6+ CPU Core Power Supplies
I RMS = ?
η TOTAL OUT ( V IN - η TOT A L 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
? I LOAD ?
?
? η TOTAL V IN ?
V V
capacitors in wide-spread use at the time of publication
have typical ESR zero frequencies below 50kHz. In the
standard application circuit, the ESR needed to support
a 30mV P-P ripple is 30mV/(40A x 0.3) = 2.5m Ω . Four
330μF/2.5V Panasonic SP (type SX) capacitors in paral-
lel provide 1.5m Ω (max) ESR. With a 2m Ω droop and
0.5m Ω PCB resistance, the typical combined ESR
results in a zero at 30kHz.
Ceramic capacitors have a high ESR zero frequency,
but applications with significant voltage positioning can
take advantage of their size and low ESR. Do not put
high-value ceramic capacitors directly across the out-
put without verifying that the circuit contains enough
voltage positioning and series PCB resistance to
ensure stability. When only using ceramic output
capacitors, output overshoot (V SOAR ) typically deter-
mines the minimum output capacitance requirement.
Unstable operation manifests itself in two related but dis-
tinctly different ways: double-pulsing and feedback loop
instability. Double-pulsing occurs due to noise on the out-
put or because the ESR is so low that there is not 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 expired. Double-
pulsing is more annoying than harmful, resulting in noth-
ing 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 inductor current with an AC current probe. Do not
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
requirement (I RMS ) imposed by the switching currents.
The multiphase Quick-PWM controllers operate out-of-
phase, while the Quick-PWM slave controllers provide
selectable out-of-phase or in-phase on-time triggering.
Out-of-phase operation reduces the RMS input current
by dividing the input current between several stag-
gered stages. For duty cycles less than 100%/ η TOTAL
per phase, the I RMS requirements may be determined
by the following equation:
where η TOTAL is the total number of out-of-phase
switching regulators. The worst-case RMS current
requirement occurs when operating with V IN =
2 η TOTAL V OUT . At this point, the above equation simpli-
fies to I RMS = 0.5 x I LOAD / η TOTAL .
For most applications, non-tantalum chemistries
(ceramic, aluminum, or OS-CON) are preferred due to
their resistance to inrush surge currents typical of sys-
tems with a mechanical switch or connector in series
with the input. If the Quick-PWM controller is operated
as the second stage of a two-stage power-conversion
system, tantalum input capacitors are acceptable. In
either configuration, 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-
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 possi-
ble on-resistance (R DS(ON) ), comes in a moderate-
sized package (i.e., one or two 8-pin SOs, DPAK, or
D 2 PAK), and is reasonably priced. Make sure that the
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-
lems may occur (see the MOSFET Gate Driver section).
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX17411GTM+ | 功能描述:电流型 PWM 控制器 IMVP7 CPU & Graphics Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX17411GTM+T | 功能描述:电流型 PWM 控制器 IMVP7 CPU & Graphics Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX17411RGTM+ | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX17411RGTM+T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX17411RGTM+TW | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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