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| 型号： | MAX1717EEG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/33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： | 1MHz |
| 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： | 24-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
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Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
V SAG =
2 × C OUT × V OUT ? K ? IN OUT ? ? t OFF ( MIN ) ?
? ? V IN ? ?
The amount of output sag is also a function of the
maximum duty factor, which can be calculated from
the on-time and minimum off-time:
? V ?
( I LOAD 1 ? I LOAD 2 ) 2 × L ? K OUT + t OFF ( MIN ) ?
? V IN ?
? ? V ? V ? ?
? ?
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:
ture. A good general rule is to allow 0.5% additional
resistance for each °C of temperature rise.
Examining the Figure 1 example with a Q 2 maximum
R DS(ON) = 5.5m Ω at T J = +25°C and 7.5m Ω at T J =
+100°C reveals the following:
I LIMIT(LOW) = 90mV / 7.5m Ω = 11.9A
and the required valley current limit is:
I LIMIT(LOW) > 14A - (0.3012) 14A = 11.9A
Therefore, the circuit can deliver the full-rated 14A
using the default ILIM threshold.
When delivering 14A of output current, the worst-case
power dissipation of Q2 is 1.48W. With a thermal resis-
tance of 60°C/W and each MOSFET dissipating 0.74W,
L =
V IN ×
V OUT ( V IN ? V OUT )
f SW × LIR × I LOAD ( MAX )
the temperature rise of the MOSFETs is 60°C/W x
0.74W = 44.5°C, and the maximum ambient tempera-
ture is +100°C - 44.5°C = +55.5°C. To operate at a
higher ambient temperature, choose lower R DS(ON)
MOSFETs or reduce the thermal resistance. You could
Example: I LOAD(MAX) = 14A, V IN = 7V, V OUT = 1.6V,
f SW = 300kHz, 30% ripple current or LIR = 0.30.
also raise the current-limit threshold, allowing operation
with a higher MOSFET junction temperature.
Connect ILIM to V CC for a default 100mV current-limit
threshold. For an adjustable threshold, connect a resistor
L =
1 . 6 V ( 7 V ? 1 . 6 V )
7 V × 300 kHz × 0 . 30 × 14 A
= 0 . 98 μ H
divider from REF to GND, with ILIM connected to the cen-
ter tap. The external adjustment range of 0.5V to 3V cor-
responds to a current-limit threshold of 50mV to 300mV.
When adjusting the current limit, use 1% tolerance resis-
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 (I PEAK ).
I PEAK = I LOAD(MAX) + (LIR / 2) I LOAD(MAX)
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 valley
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)
tors and a 10μA divider current to prevent a significant
increase of errors in the current-limit tolerance.
Output Capacitor Selection
The output filter capacitor must have low enough effective
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 energy
going from a full-load to no-load condition without tripping
the OVP circuit.
In CPU V CORE converters and other applications where
the output is subject to violent load transients, the output
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
where I LIMIT(LOW) equals the minimum current-limit
threshold voltage divided by the R DS(ON) of Q2. For the
capacitance:
R ESR ≤ V STEP / I LOAD(MAX)
MAX1717, 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.
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1717EEG+ | 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 |
| MAX1717EEG+C71058 | 功能描述:DC/DC 开关控制器 Step-Down Controller for Notebook CPU 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 |
| MAX1717EEG+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 |
| MAX1717EEG-C71058 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1717EEG-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 |
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