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| 型号： | MAX8632ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/29页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUPPLY DDR 28-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，DDR |
| 输入电压： | 2 V ~ 28 V |
| 输出数： | 1 |
| 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： | 带卷 (TR) |
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Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards
The overshoot during a full-load to no-load transient
due to stored inductor energy can be calculated as:
If the calculated V IN(MIN) is greater than the required
minimum input voltage, then the operating frequency
V SOAR =
? I LOAD ( MAX ) 2 × L
2 × C OUT × V OUT
must be reduced or output capacitance added to
obtain an acceptable V SAG . If operation near dropout is
anticipated, calculate V SAG to be sure of adequate
transient response.
Applications Information
Dropout Performance (Buck)
The output-voltage adjustable range for continuous-
conduction operation is restricted by the nonadjustable
minimum off-time one-shot. For best dropout perfor-
mance, use the slower (200kHz) on-time setting. When
working with low input voltages, the duty-factor limit
must be calculated using worst-case values for on- and
A dropout design example follows:
V OUT = 2.5V
f SW = 600kHz
K = 1.7μs
t OFF(MIN) = 450ns
V DROP1 = V DROP2 = 100mV
h = 1.5
V IN ( MIN ) = ?
2 . 5 V + 0 . 1 V
? + 0 . 1 V - 0 . 1 V = 4 . 3 V
? 1 . 5 × 450 ns ? ?
? ? ?
? ? ?
off-times. Manufacturing tolerances and internal propa-
gation delays introduce an error to the TON K-factor.
This error is greater at higher frequencies (see Table
1). Also, keep in mind that transient-response perfor-
mance 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 Design
?
?
?
? 1 -
? ?
? 1 . 7 μ s
?
?
Procedure section).
The absolute point of dropout is when the inductor cur-
rent ramps down during the minimum off-time ( ? I DOWN )
as much as it ramps up during the on-time ( ? I UP ). The
ratio h = ? I UP / ? I DOWN indicates the controller’s 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:
Voltage Positioning (Buck)
In applications where fast-load transients occur, the
output voltage changes instantly by R ESR × C OUT ×
? I LOAD . Voltage positioning allows the use of fewer out-
put capacitors for such applications, and maximizes
the output-voltage AC and DC tolerance window in
tight-tolerance applications.
Figure 9 shows the connection of OUT and FB in a volt-
age-positioned circuit. In nonvoltage-positioned cir-
cuits, the MAX8632 regulates at the output capacitor. In
voltage-positioned circuits, the MAX8632 regulates on
the inductor side of the voltage-positioning resistor.
V OUT is reduced to:
V OUT ( VPS ) = V OUT ( NO _ LOAD ) - R POS × I LOAD
V IN ( MIN ) = ?
? h × t OFF ( MIN ) ? ?
?
? ?
? ?
?
?
?
? 1 -
? ?
V OUT + V DROP 1 ?
? K
?
?
?
+ V DROP 2 - V DROP 1
PC Board Layout Guidelines
Careful PC board layout is critical to achieve low
switching losses and clean, stable operation. The
switching power stage requires particular attention. If
possible, mount all the power components on the top
side of the board, with their ground terminals flush
where V DROP1 and V DROP2 are the parasitic voltage
drops in the discharge and charge paths ( see the On-
Time One-Shot (TON) section), t OFF(MIN) is from the
Electrical Characteristics , and K is taken from Table 1.
The absolute minimum input voltage is calculated with
h = 1.
against one another. Follow these guidelines for good
PC board layout:
? Keep the high-current paths short, especially at the
ground terminals. This practice is essential for sta-
ble, jitter-free operation.
? Keep the power traces and load connections short.
This practice is essential for high efficiency. Using
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8632EVKIT | 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 |
| MAX8633ELA+ | 制造商:Maxim Integrated Products 功能描述: |
| MAX8633ELA+T | 功能描述:低压差稳压器 - LDO Dual 300mA Pin-Prog LDO RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX8633ETA+ | 制造商:Maxim Integrated Products 功能描述:LDO REG 1.5V TO 3V 0.3A 8TDFN EP - Rail/Tube |
| MAX8633ETA+T | 功能描述:低压差稳压器 - LDO Dual 300mA Pin-Prog LDO RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
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