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参数资料
| 型号： | MAX1587AETL+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/30页 |
| 文件大小： | 0K |
| 描述： | IC POWER MANAGEMENT 40-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 应用： | 手持/移动设备 |
| 电源电压： | 2.6 V ~ 5.5 V |
| 工作温度： | -40°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： | 管件 |
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High-Efficiency, Low-I Q PMICs with
Dynamic Core for PDAs and Smart Phones
source and reduces switching noise in the controller.
The impedance of the input capacitor at the switching
Table 4. Compensation Parameters
frequency should be less than that of the input source
so high-frequency switching currents do not pass
through the input source.
The output capacitor keeps output ripple small and
ensures control-loop stability. The output capacitor
must also have low impedance at the switching fre-
PARAMETER
Error-Amplifier
Transconductance, gmEA
Current-Sense Amp
Transresistance, R CS
REG1
87μS
0.5V/A
REG2
87μS
0.75V/A
REG3
68μS
1.25V/A
quency. Ceramic, polymer, and tantalum capacitors
are suitable, with ceramic exhibiting the lowest ESR
Table 5. Typical Compensation Values
and lowest high-frequency impedance.
Output ripple with a ceramic output capacitor is
approximately:
V RIPPLE = I L(PEAK) [1/(2 π x f OSC x C OUT )]
If the capacitor has significant ESR, the output ripple
component due to capacitor ESR is:
V RIPPLE(ESR) = I L(PEAK) x ESR
Output capacitor specifics are also discussed in the
Compensation and Stability section.
Compensation and Stability
The relevant characteristics for REG1, REG2, and
COMPONENT OR
PARAMETER
V OUT
Output Current
Inductor
Load-Step Droop
Loop Crossover Freq (f C )
C C
R C
C OUT
REG1
3.3V
1300mA
3.3μH
3%
100kHz
330pF
240k Ω
22μF
REG2
2.5V
900mA
6.8μH
3%
100kHz
270pF
240k Ω
22μF
REG3
1.3V
500mA
10μH
3%
100kHz
330pF
240k Ω
22μF
REG3 compensation are:
1) Transconductance (from FB_ to CC_), gm EA
2) Current-sense amplifier transresistance, R CS
3) Feedback regulation voltage, V FB (1.25V)
4) Step-down output voltage, V OUT , in V
5) Output load equivalent resistance, R LOAD = V OUT /
I LOAD
The key steps for step-down compensation are:
1) Set the compensation RC zero to cancel the R LOAD
C OUT pole.
2) Set the loop crossover at or below approximately
1/10th the switching frequency.
For example, with V IN(MAX) = 5V, V OUT = 2.5V for
REG2, and I OUT = 800mA, then R LOAD = 3.125 Ω . For
REG2, R CS = 0.75V/A and gm EA = 87μS.
Choose the crossover frequency, f C ≤ f OSC /10. Choose
100kHz. Then calculate the value of the compensation
capacitor, C C :
C C = (V FB /V OUT ) x (R LOAD /R CS ) x (gm EA /(2 π x f C ))
= (1.25/2.5) x (3.125/0.75) x (87 x 10 -6 /(6.28
x 100,000)) = 289pF
Choose 330pF, the next highest standard value.
Now select the compensation resistor, R C , so transient-
droop requirements are met. As an example, if 3% tran-
sient droop is allowed for the desired load step, the
input to the error amplifier moves 0.03 x 1.25V, or
37.5mV. The error-amplifier output drives 37.5mV x
gm EA , or I EAO = 37.5mV x 87μS = 3.26μA across R C to
provide transient gain. Find the value of R C that allows
the required load-step swing from:
R C = R CS x I IND(PK) /I EAO
where I IND(PK) is the peak inductor current. In a step-
down DC-DC converter, if L IDEAL is used, output cur-
rent relates to inductor current by:
I IND(PK) = 1.25 x I OUT
So for an 800mA output load step with V IN = 3.6V and
V OUT = 2.5V:
R C = R CS x I IND(PK) /I EAO = (0.75V/A) x
(1.25 x 0.8A)/3.26μA = 230k Ω
We choose 240k Ω . Note that the inductor does not limit
the response in this case since it can ramp at (V IN -
V OUT )/L, or (3.6V - 2.5V)/3.3μH = 242mA/μs.
The output filter capacitor is then selected so that the
C OUT R LOAD pole cancels the R C C C zero:
C OUT x R LOAD = R C x C C
For the example:
R LOAD = V OUT x I LOAD = 2.5V/0.8A =
3.125 Ω
C OUT = R C x C C /R LOAD = 240k Ω x 330pF/
3.125 Ω = 25μF
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| MAX1587AETL+ | 功能描述:直流/直流开关调节器 PMICs w/Dynamic Core for PDAs 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 |
| MAX1587AETL+T | 功能描述:直流/直流开关调节器 PMICs w/Dynamic Core for PDAs 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 |
| MAX1587AETL-T | 功能描述:直流/直流开关调节器 PMICs w/Dynamic Core for PDAs 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 |
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