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| 型号： | MAX8550ETI+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/29页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUP DDR INTEG 28TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 应用： | 控制器，DDR |
| 输入电压： | 2 V ~ 28 V |
| 输出数： | 2 |
| 输出电压： | 1.8V，2.5V，0.7 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 管件 |
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MAX8550/MAX8551
Integrated DDR Power-Supply Solutions for
Desktops, Notebooks, and Graphic Cards
light-load efficiency are made by varying the inductor
value. Generally, low inductor values produce a broad-
er efficiency vs. load curve, while higher values result in
higher full-load efficiency (assuming that the coil resis-
tance remains fixed) and less output voltage ripple.
Penalties for using higher inductor values include larger
physical size and degraded load-transient response,
especially at low input-voltage levels.
DC output accuracy specifications refer to the thresh-
old of the error comparator. When the inductor is in
continuous conduction, the MAX8550/MAX8551 regu-
late the valley of the output ripple, so the actual DC out-
put voltage is higher than the trip level by 50% of the
output ripple voltage. In discontinuous conduction
( SKIP = GND and I LOAD < I LOAD( SKIP ) ), the output volt-
age has a DC regulation level higher than the error-
comparator threshold by approximately 1.5% due to
slope compensation.
Forced-PWM Mode ( SKIP = AV DD in
MAX8550 Only)
The low-noise forced-PWM mode ( SKIP = AV DD ) dis-
ables the zero-crossing comparator, which controls the
low-side switch on-time. This forces the low-side gate-
drive waveform to constantly be the complement of the
high-side gate-drive waveform, so the inductor current
reverses at light loads while DH maintains a duty factor
of V OUT / V IN . Forced-PWM mode keeps the switching
frequency fairly constant. However, forced-PWM opera-
tion comes at a cost where the no-load V DD bias cur-
current-limit sensing, the actual peak current is greater
than the valley current-limit threshold by an amount
equal to the inductor current ripple. Therefore, the exact
current-limit characteristic and maximum load capability
are a function of the current-sense resistance, inductor
value, and input voltage. When combined with the
undervoltage-protection circuit, this current-limit method
is effective in almost every circumstance.
In forced-PWM mode, the MAX8550/MAX8551 also
implement a negative current limit to prevent excessive
reverse inductor currents when the buck regulator output
is sinking current. The negative current-limit threshold is
set to approximately 120% of the positive current limit
and tracks the positive current limit when V ILIM is adjust-
ed. The current-limit threshold is adjusted with an exter-
nal resistor-divider at ILIM. A 2μA to 20μA divider current
is recommended for accuracy and noise immunity.
The current-limit threshold adjustment range is from
25mV to 200mV. In the adjustable mode, the current-
limit threshold voltage (from PGND1 to LX) is precisely
1/10th the voltage seen at ILIM. The threshold defaults
to 50mV when ILIM is connected to AV DD . The logic
threshold for switchover to the 50mV default value is
approximately AV DD - 1V.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors do not corrupt the differ-
ential current-sense signals seen between LX and GND.
rent remains between 2mA and 20mA due to the
external MOSFET’s gate charge and switching frequen-
cy. Forced-PWM mode is most useful for reducing
audio frequency noise, improving load-transient
? I
? t
=
V IN - V OUT
L
I PEAK
response, and providing sink-current capability for
dynamic output-voltage adjustment.
Current-Limit Buck Regulator (ILIM)
Valley Current Limit
The current-limit circuit for the buck regulator portion of
the MAX8550/MAX8551 employs a unique “valley” cur-
rent-sensing algorithm that senses the voltage drop
across LX and PGND1 and uses the on-resistance of
the rectifying MOSFET (Q2 in the Typical Applications
I LOAD = I PEAK / 2
Circuit, Figure 8) as the current-sensing element. If the
magnitude of the current-sense signal is above the val-
0
ON-TIME
TIME
ley current-limit threshold, the PWM controller is not
allowed to initiate a new cycle (Figure 4). With valley
14
Figure 2. Pulse-Skipping/Discontinuous Crossover Point
Maxim Integrated
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8550ETI+ | 功能描述:电压模式 PWM 控制器 Integrated DDR Power Supply Solution RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX8550ETI+T | 功能描述:电压模式 PWM 控制器 Integrated DDR Power Supply Solution RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX8550ETI-T | 功能描述:PMIC 解决方案 RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
| MAX8550EVKIT | 功能描述:电源管理IC开发工具 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX8551ETI | 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 |
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