参数资料
| 型号： | MAX1945REUI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 6A 28TSSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 1.8V，2.5V，可调 |
| 输入电压： | 2.6 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 400kHz ~ 1.2MHz |
| 电流 - 输出： | 6A |
| 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： | 28-SOIC（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 28-TSSOP 裸露焊盘 |
1MHz, 1% Accurate, 6A Internal Switch
Step-Down Regulators
Compensation Design
The double pole formed by the inductor and the output
capacitor of most voltage-mode controllers introduces
a large phase shift, which requires an elaborate com-
pensation network to stabilize the control loop. The
MAX1945R/MAX1945S controllers utilize a current-
mode control scheme that regulates the output voltage
by forcing the required current through the external
inductor, eliminating the double pole caused by the
inductor and output capacitor, and greatly simplifying
the compensation network. A simple Type 1 compensa-
tion with a single compensation resistor (R C ) and com-
pensation capacitor (C C ) creates a stable and high
bandwidth loop (Figure 1).
An internal transconductance error amplifier compen-
sates the control loop. Connect a series resistor and
capacitor between COMP (the output of the error
amplifier) and GND, to form a pole-zero pair. The external
inductor, internal current-sense circuitry, output capaci-
tor, and external compensation circuit determine the
loop-system stability. Choose the inductor and output
capacitor based on performance, size, and cost.
Additionally, select the compensation resistor and capac-
itor to optimize control-loop stability. The component val-
ues shown in the typical application circuit yield stable
operation over a broad range of input-to-output voltages.
Compensating the voltage feedback loop depends on
the type of output capacitors used. Common capaci-
tors for output filtering: ceramic capacitors, polymer
capacitors such as POSCAPs and SPCAPs, and elec-
trolytic capacitors. Use either ceramic or polymer
capacitors. Use polymer capacitors as the output
capacitor when selecting 500kHz operation. At 500kHz
switching, the voltage feedback loop is slower (about
50kHz to 60kHz) when compared to 1MHz switching.
Therefore, a polymer capacitor’s high capacitance for a
given footprint improves the output response during a
step load change. Because of its relative low ESR fre-
quencies (about 20kHz to 80kHz), use Type 2 compen-
sation. The additional high-frequency pole introduced
in Type 2 compensation offsets the ESR zero intro-
duced by the polymer capacitors to provide continuous
attenuation above the ESR zero frequencies of the poly-
mer capacitors. However, the presence of the parasitic
capacitance at COMP and the high output impedance
of the error amplifier already provide the required atten-
uation above the ESR frequencies. The following steps
outline the design process of compensating the
MAX1945 with polymer output capacitors with the com-
ponents in the application circuits Figures 1 and 2.
Regulator DC Gain:
G DC = ? V OUT / ? V COMP = gmc ? R OUT
Load Impedance Pole Frequency:
fp LOAD = 1/(2 ? π ? C OUT ? (R OUT + R ESR ))
Load Impedance Zero Frequency:
fz ESR = 1/(2 ? π ? C OUT ? R ESR )
where R OUT = V OUT /I OUT(MAX) , and gmc = 18.2S.
The feedback divider has a gain of G FB = V FB /V OUT ,
where V FB = 0.8V. The transconductance error amplifi-
er has a DC gain, G EA(DC) , of 70dB. The compensation
capacitor, C C , and the output resistance of the error
amplifier, R OEA (20M ? ), set the dominant pole. C C and
R C set a compensation zero. Calculate the dominant
pole frequency as:
fp = 1/(2 π ? C C ? R OEA )
Determine the compensation zero frequency as:
fz EA = 1/(2 π ? C C ? R C )
For best stability and response performance, set the
closed-loop unity-gain frequency much higher than the
load-impedance pole frequency. The closed-loop unity-
gain crossover frequency must be less than one-fifth of
the switching frequency. Set the crossover frequency to
10% to 15% of the switching frequency. The loop-gain
equation at unity-gain frequency, f C , is given by:
G EA ? G DC ? (f PLOAD /f C ) ? (V FB /V OUT ) = 1
where G EA = gm EA ? R C , and gm EA = 50μS, the
transconductance of the voltage-error amplifier.
Calculate R C as:
R C = (V OUT ? f C )/(gm EA ? V FB ? ? G DC ? f PLOAD )
14
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1946ETA+T | IC USB SW SGL AUTORESET 8TDFN |
| MAX1947ETA25+T | IC REG BST SYNC 2.5V 0.25A 8TDFN |
| MAX1951AESA+T | IC REG BUCK SYNC ADJ 2A 8SOIC |
| MAX1951ESA+W | IC REG BUCK SYNC ADJ 2A 8SOIC |
| MAX1954AEUB+T | IC REG CTRLR BUCK PWM CM 10-UMAX |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1945SEUI | 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 |
| MAX1945SEUI+ | 功能描述:直流/直流开关调节器 1MHz 1% 6A Step-Down PWM 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 |
| MAX1945SEUI+T | 功能描述:直流/直流开关调节器 1MHz 1% 6A Step-Down PWM 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 |
| MAX1945SEUI-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 |
| MAX1946ETA | 制造商:Maxim Integrated Products 功能描述:SINGLE USB SWITCH WITH AUTORESET AND FAULT BL - Rail/Tube |
发布紧急采购，3分钟左右您将得到回复。