- 您现在的位置：买卖IC网 > PDF目录1839 > MAX1715EEI (Maxim Integrated Products)IC REG CTRLR BUCK PWM 28-QSOP PDF资料下载
参数资料
| 型号： | MAX1715EEI |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 18/25页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 28-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| PWM 型： | 控制器 |
| 输出数： | 2 |
| 频率 - 最大： | 620kHz |
| 占空比： | 100% |
| 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： | -40°C ~ 85°C |
| 封装/外壳： | 28-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
The inductor ripple current also impacts transient-
response performance, especially at low V IN - V OUT dif-
ferentials. Low inductor values allow the inductor
current to slew faster, replenishing charge removed
from the output filter capacitors by a sudden load step.
The amount of output sag is also a function of the maxi-
mum duty factor, which can be calculated from the on-
time and minimum off-time:
ture. A good general rule is to allow 0.5% additional
resistance for each °C of temperature rise.
Examining the 8A circuit example with a maximum
R DS(ON) = 12m Ω at high temperature reveals the fol-
lowing:
I LIMIT(LOW) = 90mV / 12m Ω = 7.5A
7.5A is greater than the valley current of 6.6A, so the
where
V SAG =
( Δ I LOAD ( MAX ) ) 2 × L
2 × C F × DUTY ( V IN ( MIN ) - V OUT )
circuit can easily deliver the full-rated 8A using the
default 100mV nominal ILIM threshold.
Output Capacitor Selection
The output filter capacitor must have low enough effec-
DUTY =
K (V OUT + 0.075V) V IN
K (V OUT + 0.075V) V OUT + min off - time
tive series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR
to satisfy stability requirements. Also, the capacitance
value must be high enough to absorb the inductor
where minimum off-time = 400ns typ (see Table 5).
Inductor Selection
The switching frequency (on-time) and operating point
(% ripple or LIR) determine the inductor value as fol-
lows:
energy going from a full-load to no-load condition with-
out tripping the overvoltage protection circuit.
In CPU V CORE converters and other applications where
the output is subject to violent load transients, the out-
put capacitor ’s size depends on how much ESR is
needed to prevent the output from dipping too low
L =
V OUT (V IN - V OUT )
V IN × f × LIR × I LOAD(MAX)
under a load transient. Ignoring the sag due to finite
capacitance:
Example: I LOAD(MAX) = 8A, V IN = 7V, V OUT = 1.6V, f =
300kHz, 35% ripple current or LIR = 0.35:
R ESR ≤
V DIP
I LOAD ( MAX )
L =
1.6V (7 - 1 × 6)
7 × 300kHz × 0.33 × 8A
= 1.6 μ H
In non-CPU applications, the output capacitor’s size
depends on how much ESR is needed to maintain an
acceptable level of output voltage ripple:
Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite
cores are often the best choice; although powdered
R ESR ≤
Vp - p
LIR × I LOAD ( MAX )
iron is inexpensive and can work well at 200kHz. The
core must be large enough not to saturate at the peak
inductor current (I PEAK ):
I PEAK = I LOAD(MAX) + [(LIR / 2) ? I LOAD(MAX) ]
Determining the Current Limit
The minimum current-limit threshold must be great
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The val-
ley of the inductor current occurs at I LOAD(MAX) minus
half of the ripple current; therefore:
I LIMIT(LOW) > I LOAD(MAX) - (LIR / 2) I LOAD(MAX)
where I LIMIT(LOW) = minimum current-limit threshold
voltage divided by the R DS(ON) of Q2. For the
MAX1715, the minimum current-limit threshold (100mV
default setting) is 90mV. Use the worst-case maximum
value for R DS(ON) from the MOSFET Q2 data sheet, and
add some margin for the rise in R DS(ON) with tempera-
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 volt-
age 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
determined by the capacity needed to prevent VSAG
and VSOAR from causing problems during load tran-
sients. Also, the capacitance must be great enough to
prevent the inductor’s stored energy from launching the
output above the overvoltage protection threshold.
Generally, once enough capacitance is added to meet
the overshoot requirement, undershoot at the rising
load edge is no longer a problem (see the VSAG equa-
tion in the Design Procedure ).
18
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1716EEG+ | IC REG CTRLR BUCK PWM CM 24-QSOP |
| MAX1717EEG+ | IC REG CTRLR BUCK PWM CM 24-QSOP |
| MAX1720EUT | IC REG SWITCHD CAP INV ADJ 6TSOP |
| MAX1721EUT-T | IC REG SWITCHED CAP INV SOT23-6 |
| MAX1724EZK50-T | IC REG BST SYNC 5V .15A TSOT23-5 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1715EEI+ | 功能描述:DC/DC 开关控制器 Dual Step-Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1715EEI+T | 功能描述:DC/DC 开关控制器 Dual Step-Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1715EEI-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1715EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX1715 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1716EEG | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
发布紧急采购，3分钟左右您将得到回复。