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参数资料
| 型号： | MAX1897ETP+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/33页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 20-TQFN |
| 标准包装： | 60 |
| 系列： | Quick-PWM™ |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 电源电压： | 4.5 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 20-WQFN 裸露焊盘 |
| 包装： | 管件 |
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Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
The slave includes a precision current-limit comparator
that supplements the master ’ s current-limit circuitry.
I PEAK
I LOAD
I LIMIT
The MAX1887/MAX1897 uses CM+ and CM- to differ-
entially sense the master ’ s inductor current across a
current-sense resistor, providing a more accurate cur-
rent limit. When the master ’ s current-sense voltage
exceeds the current limit set by ILIM in the slave (see
the Dual-Mode ILIM Input section), the open-drain cur-
rent-limit comparator pulls LIMIT low (Figure 2). Once
the master triggers the current limit, a pulse-width mod-
ulated output signal appears at LIMIT. This signal is fil-
0
I LIMIT(VALLEY) = I LOAD(MAX)
TIME
(
2 - LIR
2 η
)
tered and used to adjust the master ’ s current-limit
threshold.
High-Side, Gate Driver Supply (BST)
The gate drive voltage for the high-side, N-channel
MOSFET is generated by the flying capacitor boost cir-
Figure 3. “ Valley ” Current-Limit Threshold Point
There also is a negative current limit that prevents
excessive reverse inductor currents when V OUT is sink-
ing current. The negative current-limit threshold is set to
approximately 150% of the positive current-limit thresh-
old, and tracks the positive current limit when ILIM is
adjusted.
The MAX1887/MAX1897 uses CS+ and CS- to differen-
tially measure the current across an external sense
resistor (R CS ) connected between the inductor and out-
put capacitors. This configuration provides precise cur-
rent balancing, current limiting, and voltage positioning
cuit (Figure 4). The capacitor between BST and LX is
alternately charged from the external 5V bias supply
(V DD ) and placed in parallel with the high-side MOSFET ’ s
gate-source terminals.
On startup, the synchronous rectifier (low-side MOSFET)
forces LX to ground and charges the boost capacitor to
5V. On the second half of each cycle, the switch-mode
power supply turns on the high-side MOSFET by closing
an internal switch between BST and DH. This provides
the necessary gate-to-source voltage to turn on the high-
side switch, an action that boosts the 5V gate drive signal
above the system ’ s main supply voltage (V+).
with a 1% current-sense resistor. Reducing the sense
voltage decreases power dissipation but increases the
relative measurement error.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors don ’ t corrupt the current-
sense signals measured at CS+ and CS-. The IC should
V+
C BYP
D BST
INPUT
(V IN )
be mounted relatively close to the current-sense resistor
with short, direct traces making a Kelvin sense connec-
tion.
BST
(R BST )*
C BST
Master Current-Limit Adjustment (LIMIT)
The Quick-PWM controllers that may be used as the
master controller typically use the low-side MOSFET ’ s
on-resistance as its current-sense element. This depen-
dence on a loosely specified resistance with a large
DH
LX
N H
L
temperature coefficient causes inaccurate current limit-
ing. As a result, high current-limit thresholds are need-
ed to guarantee full-load operation under worst-case
conditions. Furthermore, the inaccurate current limit
mandates the use of MOSFETs and inductors with
excessively high current and power dissipation ratings.
MAX1887
MAX1897
( )* OPTIONAL–THE RESISTOR REDUCES
THE SWITCHING-NODE RISE TIME.
Figure 4. High-Side Gate Driver Boost Circuitry
______________________________________________________________________________________
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1897ETP+ | 功能描述:电流型 PWM 控制器 Integrated Circuits (ICs) 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 |
| MAX1897ETP+T | 功能描述:电流型 PWM 控制器 Integrated Circuits (ICs) 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 |
| MAX1897ETP-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 |
| MAX1898EUB41 | 功能描述:电池管理 Linear Charger for 1-Cell Li+ Battery RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX1898EUB41+ | 功能描述:电池管理 Linear Charger for 1-Cell Li+ Battery RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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