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| 型号： | MAX1951AESA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 2A 8SOIC |
| 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： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 5.5 V |
| 输入电压： | 2.6 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
1MHz, 2A, 2.6V to 5.5V Input, PWM DC-DC
Step-Down Regulator with Enable
nominal state. The controller response time depends on
the closed-loop bandwidth. A higher bandwidth yields
a faster response time, thus preventing the output from
deviating further from its regulating value.
Compensation Design
The double pole formed by the inductor and output
capacitor of most voltage-mode controllers introduces a
large phase shift that requires an elaborate compensation
network to stabilize the control loop. The MAX1951A uti-
lizes 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 single compensation resistor (R 1 ) and compen-
sation capacitor (C 2 ) in Figure 2 creates a stable and
high-bandwidth loop.
An internal transconductance error amplifier compen-
sates the control loop. Connect a series resistor and
capacitor between COMP (the output of the error ampli-
fier) and GND to form a pole-zero pair. The external
inductor, internal current-sensing circuitry, output
capacitor, and the external compensation circuit deter-
mine the loop system stability. Choose the inductor and
output capacitor based on performance, size, and cost.
Additionally, select the compensation resistor and
capacitor to optimize control-loop stability. The compo-
nent values shown in the typical application circuit
(Figure 2) yield stable operation over a broad range of
input-to-output voltages.
The basic regulator loop consists of a power modulator,
an output feedback divider, and an error amplifier. The
power modulator has DC gain set by g mc x R LOAD , with
a pole-zero pair set by R LOAD , the output capacitor
(C OUT ), and its ESR. The following equations define the
power modulator:
Modulator gain:
G MOD = ? V OUT / ? V COMP = g mc x R LOAD
fp EA = 1/(2 π x C 2 x R OEA )
Determine the compensation zero frequency as:
fz EA = 1/(2 π x C 2 x R 1 )
For best stability and response performance, set the
closed-loop unity-gain frequency much higher than the
modulator pole frequency. In addition, set the closed-
loop crossover unity-gain frequency less than, or equal
to 1/5 of the switching frequency. However, set the
maximum zero crossing frequency to less than 1/3 of
the zero frequency set by the output capacitance and
its ESR when using POSCAP, SPCAP, OSCON, or other
electrolytic capacitors. The loop-gain equation at the
unity-gain frequency is:
G EA(fc) x G MOD(fc) x V FB /V OUT = 1
where G EA(fc) = gm EA x R 1 , and G MOD(fc) = g mc x
R LOAD x fp MOD /f C, where gm EA = 60μS .
R 1 calculated as:
R 1 = V OUT x K/(gm EA x V FB x G MOD(fc) )
where K is the correction factor due to the extra phase
introduced by the current loop at high frequencies
(>100kHz). K is related to the value of the output
capacitance (see Table 1 for values of K vs. C). Set the
error-amplifier compensation zero formed by R 1 and C 2
at the modulator pole frequency at maximum load. C 2
is calculated as follows:
C 2 = (2 x V OUT x C OUT /(R 1 x I OUT(MAX) )
As the load current decreases, the modulator pole also
decreases; however, the modulator gain increases
accordingly, resulting in a constant closed-loop unity-
gain frequency. Use the following numerical example to
calculate R 1 and C 2 values of the typical application
circuit of Figure 2.
V OUT = 1.5V
I OUT(MAX) = 2A
Table 1. K Value
Values are for output inductance from 1.2μH
Modulator pole frequency:
fp MOD = 1/(2 x π x C OUT x (R LOAD + ESR))
Modulator zero frequency:
fz ESR = 1/(2 x π x C OUT x ESR)
where R LOAD = V OUT /I OUT(MAX) and gmc = 4.2S.
C OUT (μF)
10
22
DESCRIPTION
K
0.55 to 2.2μH. Do not use output inductors larger
0.47 than 2.2μH. Use f C = 200kHz to calculate R 1 .
The feedback divider has a gain of G FB = V FB /V OUT ,
where V FB is equal to 0.8V. The transconductance error
amplifier has a DC gain, G EA(DC), of 70dB. The com-
pensation capacitor, C 2, and the output resistance of
the error amplifier, R OEA (20M ? ), set the dominant
pole. C 2 and R 1 set a compensation zero. Calculate the
dominant pole frequency as:
C OUT = 10μF
R ESR = 0.010 ?
gm EA = 60μS
gmc = 4.2S
f SWITCH = 1MHz
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1951ESA | 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 |
| MAX1951ESA+ | 功能描述:直流/直流开关调节器 1MHz 2A 2.6-5.5V PWM DC/DC Step-Down 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 |
| MAX1951ESA+T | 功能描述:直流/直流开关调节器 1MHz 2A 2.6-5.5V PWM DC/DC Step-Down 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 |
| MAX1951ESA+TW | 功能描述:直流/直流开关调节器 1MHz 2A 2.6-5.5V PWM DC/DC Step-Down 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 |
| MAX1951ESA+W | 功能描述:直流/直流开关调节器 1MHz 2A 2.6-5.5V PWM DC/DC Step-Down 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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