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| 型号： | ADP1821ARQZ-R7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 17/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 16-QSOP |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 720kHz |
| 占空比： | 90% |
| 电源电压： | 3.7 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 标准包装 |
| 产品目录页面： | 791 (CN2011-ZH PDF) |
| 其它名称： | ADP1821ARQZ-R7DKR |
ADP1821
Solving for C I in Equation 33 yields
Next calculate C I
C I =
1
π R Z f LC
(35)
C I =
1
2 π R Z f Z 1
(43)
Use the larger value of C I from Equation 34 or Equation 35.
Because of the finite output current drive of the error amplifier,
C I needs to be less than 10 nF. If it is larger than 10 nF, choose a
larger R TOP and recalculate R Z and C I until C I is less than 10 nF.
Because of the finite output current drive of the error amplifier,
C I needs to be less than 10 nF. If it is larger than 10 nF, choose a
larger R TOP and recalculate R Z and C I until C I is less than 10 nF.
Since C HF << C I , combining Equation 29 and Equation 39 yields
=
(44)
C HF =
Next, choose the high frequency pole f P1 to be ? of f SW .
1
f P 1 f SW
2
Since C HF << C I , Equation 29 is simplified to
(36)
1
π f SW R Z
Next calculate the feedforward capacitor C FF. Assume R FF << R TOP ,
then Equation 28 is simplified to
f P 1 =
1
2 π R Z C HF
(37)
f Z 2 =
1
2 π C FF R TOP
(45)
Solving for C HF in Equation 36 and Equation 37 yields
Solving C FF in Equation 45 yields
C HF =
1
π f SW R Z
(38)
C FF =
1
2 π R TOP f Z 2
(46)
Type III Compensator
where f Z2 is obtained from Equation 40 or Equation 41.
G
(dB)
–1
S
LO
PE
+1
S
LO
PE
–1
SL
O
PE
The feedforward resistor, R FF , can be calculated by combining
Equation 30 and Equation 39
–90°
PHASE
f Z
f P
R FF =
1
π C FF f SW
(47)
–270°
C HF
Check that the calculated component values are reasonable.
For instance, capacitors smaller than about 10 pF should be
R FF
C FF
R Z
C I
avoided. In addition, the ADP1821 error amplifier has finite
output current drive, so R Z values less than 3 kΩ and C I values
FROM
V OUT
R TOP
R BOT
EA
COMP
TO PWM
greater than 10 nF should be avoided. If necessary, recalculate
the compensation network with a different starting value of R TOP . If
C HF is too small, start with a smaller value of R TOP . If R Z is too
VREF
VRAMP
small and C I is too big, start with a larger value of R TOP .
0V
Figure 19. Type III Compensation
If the output capacitor ESR zero frequency is greater than ? of
the crossover frequency, use Type III compensator as shown in
In general, aluminum electrolytic capacitors have high ESR,
therefore, a Type II compensation is adequate. However, if
several aluminum electrolytic capacitors are connected in
parallel, producing a low effective ESR, then Type III compensation
is needed. In addition, ceramic capacitors have very low ESR, on
the order of a few milliohms, requiring Type III compensation for
f P 1 = f P 2 =
1
2
f SW
(39)
ceramic output capacitors. Type III compensation offers better
performance than Type II in terms of more low frequency gain,
= =
f Z 1 = f Z 2 =
f CO f SW
4 40
1
2 π R Z C I
(40)
more phase margin, and less high frequency gain at the
crossover frequency.
or
f Z 1 = f Z 2 =
f LC
2
=
1
2 π R Z C I
(41)
Use the lower zero frequency from Equation 40 or Equation 41.
Calculate the compensator resistor, R Z , by
V IN f LC
R Z =
R TOP V RAMP f Z 1 f CO
2
(42)
Rev. C | Page 17 of 24
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADP1821-BL1-EVZ | 制造商:Analog Devices 功能描述:Evaluation Board For Step-Down DC-To-DC Controller 制造商:Analog Devices 功能描述:BLANK ADISIMPOWER EVAL ADP1821 - Boxed Product (Development Kits) |
| ADP1821-BL2-EVZ | 制造商:Analog Devices 功能描述:Evaluation Board For Step-Down DC-To-DC Controller 制造商:Analog Devices 功能描述:BLANK ADISIMPOWER EVAL ADP1821 - Boxed Product (Development Kits) |
| ADP1821-EVAL | 功能描述:电源管理IC开发工具 Evaluation Board I.C. 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 |
| ADP1822 | 制造商:AD 制造商全称:Analog Devices 功能描述:PWM, Step-Down DC-to-DC Controller with Margining and Tracking |
| ADP1822ARQZ-R7 | 功能描述:IC REG CTRLR BUCK PWM VM 24-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:75 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.3 V ~ 13.5 V 降压:是 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:0°C ~ 70°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:管件 产品目录页面:1051 (CN2011-ZH PDF) 其它名称:296-2543-5 |
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