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| 型号： | MAX1716EEG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 22/33页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 100% |
| 电源电压： | 2 V ~ 28 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： | 24-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
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High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
mal frequency is largely a function of maximum input
voltage, due to MOSFET switching losses that are pro-
portional to frequency and V+ 2 . The optimum frequency
is also a moving target, due to rapid improvements in
MOSFET technology that are making higher frequen-
cies more practical.
Inductor operating point: This choice provides trade-
offs between size vs. efficiency. Low inductor values
cause large ripple currents, resulting in the smallest
size, but poor efficiency and high output noise. The
minimum practical inductor value is one that causes the
circuit to operate at the edge of critical conduction
(where the inductor current just touches zero with every
cycle at maximum load). Inductor values lower than this
grant no further size-reduction benefit.
The MAX1716/MAX1854/MAX1855 ’ s pulse-skipping
algorithm initiates skip mode at the critical-conduction
point. Thus, the inductor operating point also deter-
mines the load-current value at which PFM/PWM
switchover occurs. The optimum point is usually found
between 20% and 50% ripple current.
The inductor ripple current impacts transient-response
performance, especially at low V IN - V OUT differentials.
Low inductor values allow the inductor current to slew
faster, replenishing charge removed from the output fil-
ter capacitors by a sudden load step. The amount of
output sag is also a function of the maximum duty fac-
tor, which can be calculated from the on-time and mini-
mum off-time:
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
iron is inexpensive and can work well at 200kHz. The
core must be large enough not to saturate at the peak
inductor current (IPEAK).
I PEAK = I LOAD(MAX) + (I LOAD(MAX) × LIR / 2)
Setting 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) - (I LOAD(MAX) × LIR / 2)
where I LIMIT(LOW) equals the minimum current-limit
threshold voltage divided by R SENSE . For the 120mV
default setting, the minimum current-limit threshold is
110mV.
Connect ILIM to V CC for a default 120mV current-limit
threshold. In the adjustable mode, the current-limit
threshold is precisely 1/10th the voltage seen at ILIM.
For an adjustable threshold, connect a resistive divider
from REF to GND, with ILIM connected to the center
tap. The external 0.5V to 2.0V adjustment range corre-
sponds to a current-limit threshold of 50mV to 200mV.
When adjusting the current limit, use 1% tolerance
resistors and a 10μA divider current to prevent a signifi-
cant increase of errors in the current-limit value.
( I LOAD 1 ? I LOAD 2 ) 2 × L × ? ? K × OUT ? ? t OFF ( MIN ) ?
?
?
2 × C OUT OUT × ? K × ?
× V
? ? t OFF ( MIN ) ?
?
?
V SAG =
? ? V + ? V OUT ? ?
? ? V ? ?
? V + ?
? V + ?
Output Capacitor Selection
The output filter capacitor must have low enough effec-
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
( )
? SW
where t OFF(MIN) is the minimum off-time (see Electrical
Characteristics ), and K is from Table 3.
Inductor Selection
The switching frequency and operating point (% ripple
or LIR) determine the inductor value as follows:
V OUT × V + ? V OUT
L =
V + × × LIR × I LOAD ( MAX )
Example: I LOAD(MAX) = 18A, V IN = 7V, V OUT = 1.6V,
f SW = 300kHz, 30% ripple current or LIR = 0.3.
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 typically 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 capacitance:
R ESR = V STEP(MAX) / I LOAD(MAX)
The actual μF 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
L =
1 . 6 V × ( 7 V ? 1 . 6 V )
7 V × 300 kHz × 0 . 30 × 18 A
= 0 . 76 μ H
capacitor is usually selected by ESR and voltage rating
rather than by capacitance value (this is true of tanta-
lums, OS-CONs, and other electrolytics).
22
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1716EEG+ | 功能描述:DC/DC 开关控制器 Adj Synchronous Step-Down 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+T | 功能描述:DC/DC 开关控制器 Adj Synchronous Step-Down 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-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 |
| MAX17175ETG+ | 制造商:Maxim Integrated Products 功能描述:BOOST REG W/INTEGRATED CHARGE PUMPS SWITCH CONTROL & HIGH-CU - Rail/Tube |
| MAX1717BEEG | 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 |
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