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参数资料
| 型号： | MAX1820XEUB+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 13/18页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK WCDMA 10-MSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 应用： | 转换器，WCDMA 功率放大器应用 |
| 输入电压： | 2.6 V ~ 5.5 V |
| 输出数： | 1 |
| 输出电压： | 0.4 V ~ 3.4 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 10-µMAX |
| 包装： | 管件 |
WCDMA Cellular Phone 600mA
Buck Regulators
Applications Information
Setting the Output Voltage (MAX1820)
The MAX1820 is optimized for highest system efficiency
when applying power to a linear PA in WCDMA hand-
sets. When transmitting at less than full power, the sup-
ply voltage to the PA is reduced (from 3.4V to as low as
0.4V) to greatly reduce battery current. Figure 4 shows
the typical WCDMA PA load profile. The use of a DC-
DC converter such as the MAX1820 dramatically
reduces battery drain in these applications.
3.4
3.0
1.0
0.4
Compensation and Stability
The MAX1820/MAX1821 are externally compensated
by placing a resistor and a capacitor (R C and C1) in
series, from COMP to GND (Figure 3). The capacitor
integrates the current from the transimpedance amplifi-
er, averaging output capacitor ripple. This sets the
device speed for transient responses and allows the
use of small ceramic output capacitors because the
phase-shifted capacitor ripple does not disturb the cur-
rent regulation loop. The resistor sets the proportional
gain of the output error voltage by a factor g m ? R C .
Increasing this resistor also increases the sensitivity of
the control loop to the output capacitor ripple.
This resistor and capacitor set a compensation zero
that defines the system’s transient response. The load
pole is a dynamic pole, shifting the pole frequency with
changes in load. As the load decreases, the pole fre-
quency shifts to the left. System stability requires that
the compensation zero must be placed properly to
ensure adequate phase margin (at least 30° at unity
gain). The following is a design procedure for the com-
pensation network:
1) Select an appropriate converter bandwidth (f C ) to
stabilize the system while maximizing transient
30
300
WCDMA PA SUPPLY CURRENT (mA)
600
response. This bandwidth should not exceed 1/5 of
the switching frequency. Use 100kHz as a reason-
able starting point.
? V O(MAX) ? ? 1 ? ? R2 ? ? 1 ?
? ? ? g m × R1+R2 ? ? ? 2 × π × f ?
C1 = ? ? ?
R1 = R2 ? OUT - 1 ?
TION C1 = ?
? ? 50 μ s ×
? ? ?
? 0.6A ? ? 0 . 75 ? ? ?
151k ? +199k ? ?
× ?
? = 341pF
Figure 4. Typical WCDMA PA Load Profile
The MAX1820 ’s output voltage is dynamically
adjustable from 0.4V to V BATT by the use of the REF
input. The gain from V REF to V OUT is internally set to
1.76. V OUT can be adjusted during operation by driving
REF with an external DAC. The MAX1820 output
responds to full-scale change in voltage and current in
<30μs.
Setting the Output Voltage (MAX1821)
The MAX1821 is intended for general-purpose step-
down applications where high efficiency is a priority.
Select an output voltage between 1.25V and V BATT by
connecting FB to a resistive divider between the output
and GND (Figure 3). Select feedback resistor R2 in the
5k ? to 30k ? range. R1 is then given by:
? V ?
? V FB ?
where V FB = 1.25V.
2) Calculate the compensation capacitor, C1, based
on this bandwidth:
? I O(MAX) ? ? R CS ? ? C ?
Resistors R1 and R2 are internal to the MAX1820; use
R1 = 151k ? and R2 = 199k ? as nominal values for cal-
culations. These resistors are external to the MAX1821
(see the Setting the Output Voltage section). Using
V OMAX = 3.4V, I OMAX = 0.6A, g m = 50μs, R CS = 0.75 ? ,
C1 is evaluated as:
? 3.4V ? ? 1 ? ? 1 99 k ? ?
3
? 1 ?
? 2 × 3 . 14 × 100 kHz ?
Selecting the nearest standard value of 330pF corre-
sponds to a 103kHz bandwidth, which is still accept-
able per the above criteria.
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1820XEUB+ | 功能描述:直流/直流开关调节器 WCDMA 600mA Buck Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1820XEUB+T | 功能描述:直流/直流开关调节器 WCDMA 600mA Buck Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1820XEUB-T | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX1820YEBC | 制造商:Maxim Integrated Products 功能描述:WCDMA CELLULAR PHONE 600MA BUCK REG - Rail/Tube |
| MAX1820YEBC+ | 制造商:Maxim Integrated Products 功能描述:CONV DC-DC SGL-OUT STEP DOWN 12UCSP - Rail/Tube |
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