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参数资料
| 型号： | MAX1791EUB+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 300kHz |
| 电源电压： | 5 V ~ 20 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
High-Efficiency, 10-Pin μMAX, Step-Down
Controllers for Notebooks
Examining the 2A circuit example with a maximum
R DS(ON) = 52m ? at +85°C temperature reveals the fol-
lowing:
I VALLEY = 90mV / 52m ? = 1.73A
Checking the corresponding I LOAD(MAX) reveals:
once enough capacitance is added to meet the over-
shoot requirement, undershoot at the rising load edge
is no longer a problem (see the V SAG equation in the
Design Procedure section).
The amount of overshoot due to stored inductor energy
can be calculated as:
I LOAD(MAX) = =
I VALLEY
1 - 0.5 LIR
1.73A
1 - 0.5 × 0.35
= 2.1A
? V ≤
LI PEAK 2
2 CV OUT
A current-sense resistor can be connected from CS to
GND to set the current limit for the device. The
MAX1762/MAX1791 use the sense resistor instead of
the R DS(ON) of Q2 to limit the current. The maximum
value of the sense resistor can be calculated with the
equation:
where I PEAK is the peak inductor current.
Stability Considerations
Stability is determined by the value of the ESR zero
(f ESR ) relative to the switching frequency (f). The point
of instability is given by the following equation:
I LIMIT = 90mV / R SENSE
Output Capacitor Selection
The output filter capacitor must have low enough effec-
where:
? ESR ≤
?
π
tive series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR
to satisfy stability requirements. In CPU V CORE convert-
? ESR ≤
1
2 × π × R ESR × C OUT
ers and other applications where the output is subject
to large 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 capacitance:
For a typical 300kHz application, the ESR zero frequen-
cy must be well below 95kHz, preferably below 50kHz.
Tantalum, Sanyo POSCAP, and Panasonic SP capaci-
tors in widespread use at the time of publication have
typical ESR zero frequencies of 20kHz. In the design
example used for inductor selection, the ESR needed
R ESR ≤
V DIP
? I LOAD(MAX)
to support a specified ripple voltage is found by the
equation:
where V DIP is the maximum tolerable transient voltage
drop. In non-CPU applications, the output capacitor’s
R ESR =
V RIPPLE(p-p)
? LIR × I LOAD
size depends on how much ESR is needed to maintain
an acceptable level of output voltage ripple:
where LIR is the inductor ripple current ratio, and I LOAD
is the average DC load. Using a LIR = 0.35 and an
R ESR ≤
V P-P
LIR × I LOAD(MAX)
average load current of 2A, the ESR needed to support
50mV P-P ripple is 71m ? .
Do not use high-value ceramic capacitors directly
where V P-P is the peak-to-peak output voltage ripple.
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 tantalum, SP, POS, and other electrolytic-type
capacitors).
When using low-capacity filter capacitors such as
ceramics, capacitor size is usually determined by the
capacity needed to prevent V SAG and V SOAR from
causing problems during load transients. Generally,
across the fast feedback inputs (FB to GND) without
taking precautions to ensure stability. Large ceramic
capacitors can have a high-ESR zero frequency and
cause erratic, unstable operation. However, it is easy to
add enough series resistance by placing the capaci-
tors a couple of inches downstream from the junction of
the inductor and FB pin.
Unstable operation manifests itself in two related but dis-
tinctly different ways: double-pulsing and fast-feedback
loop instability. Double pulsing occurs due to noise on
the output or because the ESR is so low that there is not
enough voltage ramp in the output voltage signal. This
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1791EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX1791 MAX1762 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 |
| MAX1792EUA15 | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1792EUA15+ | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1792EUA15+T | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1792EUA15-T | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
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