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参数资料
| 型号： | MAX8643AETG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 13/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 3A 24TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 75 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 3.2 V |
| 输入电压： | 2.35 V ~ 3.6 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 500kHz ~ 2MHz |
| 电流 - 输出： | 3A |
| 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： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 24-TQFN-EP（4x4） |
3A, 2MHz Step-Down Regulator
with Integrated Switches
Due to the underdamped nature of the output LC dou-
COMPENSATION
TRANSFER
FUNCTION
DOUBLE POLE
OPEN-LOOP
GAIN
THIRD
POLE
ble pole, set the two zero frequencies of the type III
compensation less than the LC double-pole frequency
to provide adequate phase boost. Set the two zero fre-
quencies to 80% of the LC double-pole frequency.
Hence:
GAIN (dB)
POWER-STAGE
TRANSFER
SECOND
POLE
R 1 =
1
0 . 8 x C 1
x
L x C O x ( R O + ESR )
R L + R O
FUNCTION
FIRST AND SECOND ZEROS
C 3 =
1
0 . 8 x R 3
x
L x C O x ( R O + ESR )
R L + R O
Figure 4. Type III Compensation Illustration
Setting the second compensation pole, f P2_EA , at
f Z_ESR yields:
f Z 2 _ EA =
1
2 π x R 3 x C 3
R 2 =
C O x ESR
C 3
f P 3 _ EA =
1
2 π x R 1 x C 2
Set the third compensation pole at 1/2 of the switching
frequency to gain some phase margin. Calculate C2 as
f P 2 _ EA =
C 2 =
1
2 π x R 2 x C 3
The above equations are based on the assumptions that
C1>>C2 and R3>>R2 are true in most applications.
Placements of these poles and zeros are determined by
the frequencies of the double pole and ESR zero of the
power transfer function. It is also a function of the
desired closed-loop bandwidth. The following section
outlines the step-by-step design procedure to calculate
the required compensation components for the
MAX8643A. When the output voltage of the MAX8643A
is programmed to a preset voltage, R3 is internal to the
IC and R4 does not exist (Figure 3b).
When externally programming the MAX8643A (Figure
3a), the output voltage is determined by:
follows:
1
π x R 1 x f S × 2
The above equations provide accurate compensation
when the zero-cross frequency is significantly higher
than the double-pole frequency. When the zero-cross
frequency is near the double-pole frequency, the actual
zero-cross frequency is higher than the calculated fre-
quency. In this case, lowering the value of R1 reduces
the zero-cross frequency. Also, set the third pole of the
type III compensation close to the switching frequency
if the zero-cross frequency is above 200kHz to boost
the phase margin. The recommended range for R3 is
2k ? to 10k ? . Note that the loop compensation remains
unchanged if only R4’s resistance is altered to set dif-
ferent outputs.
R 4 =
0 . 6 × R 3
( V OUT ? 0 . 6 )
Soft-Starting into a Prebiased Output
When the PREBIAS pin is left unconnected, the
MAX8643A is capable of soft-starting up into a prebiased
The zero-cross frequency of the closed-loop, f C , should
be between 10% and 20% of the switching frequency,
f S . A higher zero-cross frequency results in faster tran-
sient response. Once f C is chosen, C1 is calculated
from the following equation:
output without discharging the output capacitor. This
type of operation is also termed monotonic startup.
However, in order to avoid output voltage glitches during
soft-start, it should be ensured that the inductor current
is in continuous conduction mode during the end of the
soft-start period. This is done by satisfying the following
2 x π x R 3 x ( 1 + L ) × f C
C O × ≥ P ? P
C 1 =
1 . 5625 V IN
R
R O
equation:
V O I
t SS 2
______________________________________________________________________________________
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8643AETG/V+ | 功能描述:直流/直流开关调节器 3A 2MHz Step-Down Regulator w/Switch 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 |
| MAX8643AETG/V+T | 功能描述:直流/直流开关调节器 3A 2MHz Step-Down Regulator w/Switch 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 |
| MAX8643AETG+ | 功能描述:直流/直流开关调节器 3A 2MHz Step-Down Regulator w/Switch 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 |
| MAX8643AETG+T | 功能描述:直流/直流开关调节器 3A 2MHz Step-Down Regulator w/Switch 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 |
| MAX8643ETG+ | 功能描述:直流/直流开关调节器 3A 2MHz Step-Down Regulator w/Switch 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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