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| 型号： | MAX8553EEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/24页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR BUCK PWM 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 系列： | Quick-PWM™ |
| 应用： | 控制器，DDR，DDR2 |
| 输入电压： | 4.5 V ~ 28 V |
| 输出数： | 1 |
| 输出电压： | 可调 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-QSOP |
| 包装： | 带卷 (TR) |
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
Setting the Current Limit
Constant Current Limit
The adjustable current limit accommodates MOSFETs
with a wide range of on-resistance values. The current-
limit threshold is adjusted with an external resistor con-
nected from ILIM to GND (R ILIM_ ). The adjustment
range is 50mV to 200mV measured across the low-side
MOSFET. The value of R ILIM is calculated using the fol-
lowing formula:
MAX8553
DH
V OUT
R ILIM = 10 × × R DS ( ON )
LX
I VALLEY
5 μ A
DL
where I VALLEY is the valley current limit and R DS(ON) is
the on-resistance of the low-side MOSFET. To avoid
reaching the current at a lower current than expected,
use the maximum value for R DS(ON) at elevated junc-
tion temperature. Refer to the MOSFET manufacturer’s
data sheet for maximum values.
R ILIM
R FOBK
ILIM
PGND
Foldback Current Limit
Foldback current limit is used to reduce power dissipa-
tion during overload and short-circuit conditions. This is
accomplished by lowering the current-limit threshold as
the output voltage drops due to the overload.
To use foldback current limit, connect a resistor
(R FOBK ) from ILIM to the output, and connect a resistor
(R ILIM ) from ILIM to GND ( Figure 5). The values of R ILIM
and R FOBK are calculated as follows:
First, select the percentage of foldback, P FB . This per-
cent corresponds to the current limit when V OUT equals
zero divided by the current limit when V OUT equals its
nominal voltage. Typical values range from 15% to
Figure 5. Setting the Foldback Current Limit with Two
Resistors, RILIM and RFOBK
Adjusting the Switching Frequency
The switching frequency of the MAX8553/MAX8554 can
be lowered from the value set by FSEL by adding a
resistor voltage-divider to EN/HSD (HSD) as shown in
Figure 6. This voltage-divider lowers the voltage the IC
measures on EN/HSD (HSD), which increases the on-
time. The switching frequency with the added resistor-
divider is calculated as follows:
30%. To solve for the resistor values, use the following
equations:
f S ?
1
K × N
×
R 2
R 1 + R 2
R FOBK =
P FB × V OUT
5 μ A ( 1 - P FB )
where K = 1.7μs and N is given in Tables 1 and 2. To set
the frequency, select a value for R2 between 10k ? and
100k ? , then calculate R1 from the following equation:
R ILIM =
10 × R DS ( ON ) × I VALLEY × ( 1 - P FB ) × R FOBK
V OUT - ( 10 × R DS ( ON ) × I VALLEY × ( 1 - P FB ) )
R 1 =
1
K × N
×
R 2
f S
- R 2
If R ILIM results in a negative number, select another low-
side MOSFET with lower R DS(ON) or increase P FB or a
combination of both for the best compromise of cost,
With the minimum input voltage, make sure that the
voltage present at EN/HSD (HSD) is greater than 1.5V
when the resistor-divider is used:
efficiency, and lower short-circuit power dissipation.
V IN(MIN) × R2
R 1 + R 2
> 1 . 5 V
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8554EEE | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX8554EEE+ | 功能描述:电流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX8554EEE+T | 功能描述:电流型 PWM 控制器 4.5-28V Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX8554EEE-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX8554EVKIT | 功能描述:电流型 PWM 控制器 Evaluation Kit for the MAX8553 MAX8554 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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