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| 型号： | MAX8764ETP+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/23页 |
| 文件大小： | 0K |
| 描述： | IC CNTRL STP DWN HS 20-TQFN |
| 标准包装： | 60 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 2 V ~ 28 V |
| 输出数： | 1 |
| 输出电压： | 1.8V，2.5V，1 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WQFN 裸露焊盘 |
| 供应商设备封装： | 20-TQFN-EP（5x5） |
| 包装： | 管件 |
High-Speed, Step-Down Controller with
Accurate Current Limit for Notebook Computers
V SAG =
where
( ? I LOAD(MAX) ) 2 × L
2 × C OUT × DUTY (V IN(MIN) - V OUT )
a)
LX
b)
LX
DUTY =
K (V OUT + 0.075V)/ V IN
K (V OUT + 0.075V)/ V OUT + min off - time
MAX8764
DL
MAX8764
DL
and minimum off-time = 400ns (typ) (see Table 5 for K
values).
The amount of overshoot during a full-load to no-load
transient due to stored inductor energy can be calculated
as:
CS
CS
L =
V OUT
f x LIR x I LOAD ( MAX )
Figure 8. Current-Sense Circuits
transient requirements, yet have high enough ESR to sat-
Setting the Current Limit
For most applications, set the MAX8764 current limit by
the following procedure:
1) Determine the minimum (valley) inductor current
I L(MIN) under conditions when V IN is small, V OUT is
large, and load current is maximum. The minimum
inductor current is I LOAD minus half the ripple cur-
isfy stability requirements.
For CPU core voltage converters and other applications
where the output is subject to violent load transients, the
output capacitor’s size depends on how much ESR is
needed to prevent the output from dipping too low under
a load transient. Ignoring the sag due to finite capaci-
tance:
rent (Figure 4).
2) The sense resistor determines the achievable
current-limit accuracy. There is a trade-off between
R ESR ≤
V DIP
I LOAD(MAX)
current-limit accuracy and sense-resistor power dis-
sipation. Most applications employ a current-sense
voltage of 50mV to 100mV. Choose a sense resistor
In nonCPU applications, the output capacitor’s size often
depends on how much ESR is needed to maintain an
acceptable level of output voltage ripple:
so that:
R SENSE = CS Threshold Voltage / I L(MIN)
R ESR ≤
V P-P
LIR × I LOAD(MAX)
Extremely cost-sensitive applications that do not
require high-accuracy current sensing can use the on-
resistance of the low-side MOSFET switch in place of
the sense resistor by connecting CS to LX (Figure 8b).
Use the worst-case value for R DS(ON) from the MOSFET
Q2 data sheet, and add a margin of 0.5%/°C for the
rise in R DS(ON) with temperature. Then use that
R DS(ON) value and I L(MIN) from step 1 above to deter-
mine the CS threshold voltage. If the default 100mV
threshold is unacceptable, set the value as in step 2
above.
In all cases, ensure an acceptable CS threshold volt-
age despite inaccuracies in resistor values.
Output Capacitor Selection
The output filter capacitor must have low enough effective
series resistance (ESR) to meet output ripple and load-
The actual microfarad capacitance value required relates
to the physical size needed to achieve low ESR, as well
as to the chemistry of the capacitor technology. Thus, the
capacitor is usually selected by ESR and voltage rating
rather than by capacitance value (this is true of tantalums,
OS-CONs, and other electrolytics).
When using low-capacity filter capacitors, such as
ceramic or polymer types, capacitor size is usually deter-
mined by the capacity needed to prevent V SAG and
V SOAR from causing problems during load transients.
Generally, once enough capacitance is added to meet
the overshoot requirement, undershoot at the rising load
edge is no longer a problem (also, see the V SAG and
V SOAR equation in the Transient Response section).
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8764ETP+ | 功能描述:电流型 PWM 控制器 High-Speed 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 |
| MAX8764ETP+T | 功能描述:电流型 PWM 控制器 High-Speed 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 |
| MAX8764ETP-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 |
| MAX8765AETI+ | 功能描述:电池管理 Multichemistry Battery Charger 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 |
| MAX8765AETI+T | 功能描述:电池管理 Multichemistry Battery Charger 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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