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| 型号： | MAX8707ETL+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 27/37页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR MULTIPHASE 40TQFN |
| 标准包装： | 2,500 |
| 应用： | 控制器，AMD Hammer CPU 电源 |
| 输入电压： | 4.5 ~ 5.5 V |
| 输出数： | 4 |
| 输出电压： | 0.8 ~ 1.55 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 40-WFQFN 裸露焊盘 |
| 供应商设备封装： | 40-TQFN-EP（6x6） |
| 包装： | 带卷 (TR) |
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Multiphase, Fixed-Frequency Controller for
AMD Hammer CPU Core Power Supplies
results in high light-load efficiency. Trade-offs in PFM
noise vs. light-load efficiency are made by varying the
inductor value. Generally, low inductor values produce
a broader efficiency vs. load curve, while higher values
result in higher full-load efficiency (assuming that the
coil resistance remains fixed) and less output voltage
ripple. Penalties for using higher inductor values
include larger physical size and degraded load-tran-
sient response (especially at low input-voltage levels).
Current Sense
The output current of each phase is sensed differential-
t ON(SKIP) =
V OUT
V IN f SW
I IDLE
I LOAD ≈ I LOAD(SKIP)
2
ly. Each phase of the MAX8707 has an independent
return path for fully differential current-sense. A low off-
0
ON-TIME
TIME
set voltage and high-gain (10V/V) differential current
amplifier at each phase allow low-resistance current-
sense resistors to be used to minimize power dissipa-
tion. Sensing the current at the output of each phase
offers advantages, including less noise sensitivity, more
Figure 6. Pulse-Skipping/Discontinuous Crossover Point
accurate current sharing between phases, and the flexi-
bility of using either a current-sense resistor or the DC
resistance of the output inductor.
L ESL
R SENSE
= R EQ C SENSE
Using the DC resistance (R DCR ) of the output inductor
allows higher efficiency. In this configuration, the initial
tolerance and temperature coefficient of the inductor ’ s
DCR must be accounted for in the output-voltage
droop-error budget. This current-sense method uses an
RC filtering network to extract the current information
from the output inductor ( Figure 7). The time constant
of the RC network should match the inductor ’ s time
constant (L/R DCR ):
where L ESL is the equivalent series inductance of the
current-sense resistor, R SENSE is the current-sense
resistance value, C SENSE is the compensation capaci-
tor, and R EQ is the equivalent compensation resistance.
Current Balance
The fixed-frequency, multiphase, current-mode archi-
tecture automatically forces the individual phases to
remain current balanced. After the oscillator triggers an
on-time, the controller does not terminate the on-time
L
R DCR
= R EQ C SENSE
until the amplified differential current-sense voltage
reaches the integrated threshold voltage (V REF - V TRC ).
This control scheme regulates the peak inductor cur-
where C SENSE is the sense capacitor and R EQ is the
equivalent sense resistance. To minimize the current-
sense error due to the current-sense inputs ’ bias cur-
rent (I CSP _ and I CSN _), choose R EQ less than 2k ? and
use the above equation to determine the sense capaci-
tance (C SENSE ). Choose capacitors with 5% tolerance
and resistors with 1% tolerance specifications.
Temperature compensation is recommended for this
current-sense method.
When using a current-sense resistor for accurate out-
put-voltage positioning (CRSP to CRSN for the
MAX8707), differential RC-filter circuits should be used
to cancel the equivalent series inductance of the cur-
rent-sense resistor ( Figure 7). Similar to inductor DCR-
sensing methods, the RC filter ’ s time constant should
match the L/R time constant formed by the current-
sense resistor ’ s parasitic inductance:
rent of each phase, forcing them to remain properly
balanced. Therefore, the average inductor-current vari-
ation depends mainly on the variation in the current-
sense element and inductance value.
Peak/Average Current Limit
The MAX8707 current-limit circuit employs a fast peak
inductor current-sensing algorithm. Once the current-
sense signal (CSP to CSN) of the active phase exceeds
the peak current-limit threshold, the PWM controller ter-
minates the on-time. The MAX8707 also includes a
slower average current sense that uses a current-sense
resistor between CRSP and CRSN to accurately limit
the inductor current. When this average current-sense
threshold is exceeded, the current-limit circuit lowers
the peak current-limit threshold, effectively lowering the
average inductor current. See the Current Limit section
in the Design Procedure section.
______________________________________________________________________________________
27
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| MAX8708ETJ | 制造商:Maxim Integrated Products 功能描述:AMD CPU CORE SUPPLY - Rail/Tube |
| MAX8708ETJ-T | 制造商:Maxim Integrated Products 功能描述:AMD CPU CORE SUPPLY - Tape and Reel |
| MAX8709AETI | 功能描述:显示驱动器和控制器 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 |
| MAX8709AETI+ | 功能描述:显示驱动器和控制器 CCFL Backlight Controller w/SMBus 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 |
| MAX8709AETI+T | 功能描述:显示驱动器和控制器 CCFL Backlight Controller w/SMBus 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 |
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