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参数资料
| 型号： | MAX1843ETI+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 2.7A 28TQFN |
| 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： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 1.5V，1.8V，2.5V，可调 |
| 输入电压： | 3 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 2.7A |
| 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： | 28-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Synchronous Rectification in TQFN Package
Soft-Start
Soft-start allows a gradual increase of the internal cur-
rent limit to reduce input surge currents at startup and
at exit from shutdown. A timing capacitor, C SS , placed
from SS to GND sets the rate at which the internal cur-
rent limit is changed. Upon power-up, when the device
SHDN
0
1.8V
comes out of undervoltage lockout (2.6V typ) or after
the SHDN pin is pulled high, a 4μA constant-current
source charges the soft-start capacitor and the voltage
V SS (V)
0
0.7V
on SS increases. When the voltage on SS is less than
approximately 0.7V, the current limit is set to zero. As
I LIMIT (A)
I LIMIT
the voltage increases from 0.7V to approximately 1.8V,
the current limit is adjusted from 0 to the current-limit
threshold (see the Electrical Characteristics ). The volt-
age across the soft-start capacitor changes with time
according to the equation:
0
Figure 5. Soft-Start Current-Limit Over Time
t
V SS =
4 μ A × t
C SS
Circuit Layout and Grounding
Good layout is necessary to achieve the MAX1843’s
intended output power level, high efficiency, and low
V SS ? 0 . 7 V
SSI LIMIT = × I LIMIT
The soft-start current limit varies with the voltage on the
soft-start pin, SS, according to the equation:
1 . 1 V
where I LIMIT is the current threshold from the Electrical
Characteristics .
The constant-current source stops charging once the
voltage across the soft-start capacitor reaches 1.8V
(Figure 5).
Frequency Variation with Output Current
The operating frequency of the MAX1843 is determined
primarily by t OFF (set by R TOFF ), V IN , and V OUT as
shown in the following formula:
f PWM = (V IN - V OUT - V PMOS ) / [t OFF (V IN - V PMOS +
V NMOS )]
However, as the output current increases, the voltage
drop across the nMOS and pMOS switches increases
and the voltage across the inductor decreases. This
causes the frequency to drop. The change in frequency
can be approximated with the following formula:
? f PWM = -I OUT x R PMOS / (V IN x t OFF )
where R PMOS is the resistance of the internal MOSFETs
(90m ? typ).
noise. Good layout includes the use of ground planes,
careful component placement, and correct routing of
traces using appropriate trace widths. The following
points are in order of decreasing importance:
1) Minimize switched-current and high-current ground
loops. Connect the input capacitor’s ground, the out-
put capacitor ’s ground, and PGND. Connect the
resulting island to GND at only one point.
2) Connect the input filter capacitor less than 5mm
away from IN. The connecting copper trace carries
large currents and must be at least 1mm wide,
preferably 2.5mm.
3) Place the LX node components as close together
and as near to the device as possible. This reduces
resistive and switching losses as well as noise.
4) Ground planes are essential for optimum perfor-
mance. In most applications, the circuit is located on
a multilayer board and full use of the four or more
layers is recommended. For heat dissipation, con-
nect the exposed backside pad to a large analog
ground plane, preferably on a surface of the board
that receives good airflow. If the ground plane is
located on the IC surface, make use of the N.C. pins
adjacent to GND to lower thermal resistance to the
ground plane. If the ground is located elsewhere,
use several vias to lower thermal resistance. Typical
applications use multiple ground planes to minimize
thermal resistance. Avoid large AC currents through
the analog ground plane.
Chip Information
TRANSISTOR COUNT: 3662
______________________________________________________________________________________
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1843ETI+ | 功能描述:直流/直流开关调节器 2.7A 1MHz 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 |
| MAX1843ETI+T | 功能描述:直流/直流开关调节器 2.7A 1MHz 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 |
| MAX1844EEP | 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 |
| MAX1844EEP+ | 功能描述:电流型 PWM 控制器 Step-Down 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 |
| MAX1844EEP+T | 功能描述:电流型 PWM 控制器 Step-Down 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 |
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