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| 型号： | MAX17410GTM+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 43/45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
R FB =
R SENSE m ( FB )
? + V ?
V FB DROOP DIS
V IN ( MIN ) = η TOTAL ?
?
Current-Balance Compensation (CCI)
The current-balance compensation capacitor (C CCI )
integrates the difference between the main and sec-
ondary current-sense voltages. The internal compensa-
tion resistor (R CCI = 200k Ω ) improves transient
response by increasing the phase margin. This allows
the dynamics of the current-balance loop to be opti-
mized. Excessively large capacitor values increase the
integration time constant, resulting in larger current dif-
ferences between the phases during transients.
Excessively small capacitor values allow the current
loop to respond cycle-by-cycle but can result in small
DC current variations between the phases. Likewise,
excessively large resistor values can also cause DC
current variations between the phases. Small resistor
values reduce the phase margin, resulting in marginal
stability in the current-balance loop. For most applica-
tions, a 470pF capacitor from CCI to the switching reg-
ulator’s output works well.
Connecting the compensation network to the output
(V OUT ) allows the controller to feed-forward the output
voltage signal, especially during transients. To reduce
noise pick-up in applications that have a widely distrib-
uted layout, it is sometimes helpful to connect the com-
pensation network to the quiet analog ground rather
than V OUT .
Voltage Positioning and
Loop Compensation
Voltage positioning dynamically lowers the output volt-
age in response to the load current, reducing the out-
put capacitance and processor ’s power dissipation
requirements. The controller uses a transconductance
amplifier to set the transient and DC output-voltage
droop (Figure 2) as a function of the load. This adjusta-
bility allows flexibility in the selected current-sense
resistor value or inductor DCR, and allows smaller cur-
rent-sense resistance to be used, reducing the overall
power dissipated.
Steady-State Voltage Positioning
Connect a resistor (R FB ) between FB and V OUT to set
the DC steady-state droop (load line) based on the
required voltage-positioning slope (R DROOP ):
R DROOP
G
where the effective current-sense resistance (R SENSE )
depends on the current-sense method (see the Current
Sense section), and the voltage-positioning amplifier’s
transconductance (G m(FB) ) is typically 1.2mS as defined
in the Electrical Characteristics table. The controller uses
the CSPAVG pin to get the average inductor current
from the positive current-sense averaging network.
When the inductors’ DCR is used as the current-sense
element (R SENSE = R DCR ), the current-sense inputs
should include an NTC thermistor to minimize the tem-
perature dependence of the voltage-positioning slope.
Minimum Input Voltage Requirements
and Dropout Performance
The output-voltage adjustable range for continuous-
conduction operation is restricted by the nonadjustable
minimum off-time one-shot and the number of phases.
For best dropout performance, use the slower (200kHz)
on-time settings. When working with low input voltages,
the duty-factor limit must be calculated using worst-
case values for on- and off-times. Manufacturing toler-
ances and internal propagation delays introduce an
error to the on-times. This error is greater at higher fre-
quencies. Also, keep in mind that transient response
performance of buck regulators operated too close to
dropout is poor, and bulk output capacitance must
often be added (see the V SAG equation in the
Transient Response section).
The absolute point of dropout is when the inductor cur-
rent ramps down during the minimum off-time ( Δ I DOWN )
as much as it ramps up during the on-time ( Δ I UP ). The
ratio h = Δ I UP / Δ I DOWN is an indicator of the ability to
slew the inductor current higher in response to
increased load, and must always be greater than 1. As
h approaches 1, the absolute minimum dropout point,
the inductor current cannot increase as much during
each switching cycle and V SAG greatly increases
unless additional output capacitance is used.
A reasonable minimum value for h is 1.5, but adjusting
this up or down allows trade-offs between V SAG , output
capacitance, and minimum operating voltage. For a
given value of h, the minimum operating voltage can be
calculated as:
- V
? ? 1 - η TOTAL h × t OF F ( MIN ) f SW ? ?
+ V CHG - V DIS + V DROOP
where η TOTAL is the total number of out-of-phase
switching regulators, V FB is the voltage-positioning
droop, V DIS and V CHG are the parasitic voltage drops
in the discharge and charge paths (see the on-time
one-shot parameter), t OFF(MIN) is from the Electrical
Characteristics table. The absolute minimum input volt-
age is calculated with h = 1.
______________________________________________________________________________________
43
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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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