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参数资料
| 型号： | MAX8855ETJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 5A DL 32TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 3.24 V |
| 输入电压： | 2.35 V ~ 3.6 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 1MHz ~ 2MHz |
| 电流 - 输出： | 5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
Dual, 5A, 2MHz Step-Down Regulators
V RIPPLE ( C ) =
f P 1 _ LC = f P 2 _ LC =
2 π × L × C O × ? O
? R O + R L ?
V RIPPLE ( ESL ) = × ESL
f Z _ ESR =
Output-Capacitor Selection
The key selection parameters for the output capacitor
are capacitance, ESR, ESL, and voltage-rating require-
ments. These affect the overall stability, output ripple
voltage, and transient response of the DC-DC convert-
er. The output ripple occurs due to variations in the
charge stored in the output capacitor, the voltage drop
due to the capacitor’s ESR, and the voltage drop due to
the capacitor’s ESL. Calculate the output-voltage ripple
due to the output capacitance, ESR, and ESL as:
V RIPPLE = V RIPPLE ( C ) + V RIPPLE ( ESR ) + V RIPPLE ( ESL )
where the output ripple due to output capacitance,
ESR, and ESL is:
I P ? P
8 × C OUT × f S
V RIPPLE ( ESR ) = I P ? P × ESR
I P ? P
t ON
After a short time, the controller responds by regulating
the output voltage back to its predetermined value. The
controller response time depends on the closed-loop
bandwidth. A higher bandwidth yields a faster
response time, preventing the output from deviating fur-
ther from its regulating value. See the Compensation
Design and Safe-Starting into a Prebiased Output sec-
tions for more details.
Compensation Design
The power-stage transfer function consists of one dou-
ble pole and one zero. The double pole is introduced
by the output filtering inductor, L, and the output filter-
ing capacitor, C O . The ESR of the output filtering
capacitor determines the zero. The double pole and
zero frequencies are given as follows:
1
? R + ESR ?
?
1
2 π × ESR × C O
where R L is equal to the sum of the output inductor’s
V RIPPLE ( ESL ) = × ESL
or:
I P ? P
t OFF
DC resistance and the internal switch resistance,
R DS(ON) . A typical value for R DS(ON) is 35m Ω . R O is the
output load resistance, which is equal to the rated out-
put voltage divided by the rated output current. ESR is
the total ESR of the output-filtering capacitor. If there is
I P ? P = IN OUT × OUT
whichever is greater.
It should be noted that the above ripple voltage compo-
nents add vectrorially rather than algebraically, thus
making V RIPPLE a conservative estimate.
The peak inductor current (I P-P ) is:
V ? V V
f S × L V IN
Use these equations for initial capacitor selection.
Determine final values by testing a prototype or an eval-
uation circuit. A smaller ripple current results in less out-
put-voltage ripple. Since the inductor ripple current is a
function of the inductor value, the output-voltage ripple
decreases with larger inductance. Use ceramic capaci-
tors for low ESR and low ESL at the switching frequency
of the converter. The low ESL of ceramic capacitors
makes ripple voltages due to ESL negligible.
Load-transient response depends on the selected out-
put capacitance. During a load transient, the output
more than one output capacitor of the same type in par-
allel, the value of the ESR in the above equation is
equal to that of the ESR of a single-output capacitor
divided by the total number of output capacitors.
The high-switching-frequency range of the MAX8855/
MAX8855A allows the use of ceramic output capacitors.
Since the ESR of ceramic capacitors is typically very
low, the frequency of the associated transfer-function
zero is higher than the unity-gain crossover frequency,
f C , and the zero cannot be used to compensate for the
double pole created by the output filtering inductor and
capacitor. The double pole produces a gain drop of
40dB and a phase shift of 180° per decade. The error
amplifier must compensate for this gain drop and phase
shift to achieve a stable high-bandwidth closed-loop
system. Therefore, use type III compensation as shown
in Figure 4. Type III compensation possesses three
poles and two zeros with the first pole, f P1_EA , located at
0Hz (DC). Locations of other poles and zeros of type III
compensation are given by:
instantly changes by ESR x Δ I LOAD . Before the con-
troller can respond, the output deviates further,
depending on the inductor and output capacitor values.
f Z 1 _ EA =
1
2 π × R 7 × C 9
14
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8855ETJ+ | 功能描述:直流/直流开关调节器 Dual 5A 2MHz Step-Down 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 |
| MAX8855ETJ+T | 功能描述:直流/直流开关调节器 Dual 5A 2MHz Step-Down 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 |
| MAX8855EVKIT+ | 功能描述:电源管理IC开发工具 MAX8855 Eval Kit 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 |
| MAX8856ETD+ | 制造商:Maxim Integrated Products 功能描述:USB/AC ADAPTER, LI+ LINEAR BATTERY CHARGER WITH INTEGRATED - Bulk |
| MAX8856ETD+T | 功能描述:电池管理 USB/AC Adapter Li+ Linear Bat Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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