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参数资料
| 型号： | MAX797CSE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 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，混合 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 96% |
| 电源电压： | 4.5 V ~ 30 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： | 0°C ~ 70°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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Step-Down Controllers with
Synchronous Rectifier for CPU Power
Three key inductor parameters must be specified:
inductance value (L), peak current (I PEAK ), and DC
resistance (R DC ). The following equation includes a
constant LIR, which is the ratio of inductor peak-to-
peak AC current to DC load current. A higher value of
LIR allows smaller inductance, but results in higher
losses and ripple. A good compromise between size
and losses is found at a 30% ripple current to load cur-
rent ratio (LIR = 0.3), which corresponds to a peak
inductor current 1.15 times higher than the DC load
current.
may be used in place of I PEAK if the inductor value has
been set for LIR = 0.3 or less (high inductor values)
and 300kHz operation is selected. Low-inductance
resistors, such as surface-mount metal-film resistors,
are preferred.
80mV
R SENSE = ————
I PEAK
Input Capacitor Value
Place a small ceramic capacitor (0.1μF) between V+
where:
V OUT (V IN(MAX) - V OUT )
L = ———————————
V IN(MAX) x f x I OUT x LIR
f = switching frequency, normally 150kHz or
300kHz
I OUT = maximum DC load current
LIR = ratio of AC to DC inductor current,
typically 0.3
and GND, close to the device. Also, connect a low-ESR
bulk capacitor directly to the drain of the high-side
MOSFET. Select the bulk input filter capacitor accord-
ing to input ripple-current requirements and voltage rat-
ing, rather than capacitor value. Electrolytic capacitors
that have low enough ESR to meet the ripple-current
requirement invariably have more than adequate
capacitance values. Aluminum-electrolytic capacitors
such as Sanyo OS-CON or Nichicon PL are preferred
√ V OUT (V IN - V OUT )
The peak inductor current at full load is 1.15 x I OUT if
the above equation is used; otherwise, the peak current
can be calculated by:
V OUT (V IN(MAX) - V OUT )
I PEAK = I LOAD + ———————————
2 x f x L x V IN(MAX)
The inductor’s DC resistance is a key parameter for effi-
ciency performance and must be ruthlessly minimized,
preferably to less than 25m ? at I OUT = 3A. If a stan-
dard off-the-shelf inductor is not available, choose a
core with an LI 2 rating greater than L x I PEAK2 and wind
it with the largest diameter wire that fits the winding
area. For 300kHz applications, ferrite core material is
strongly preferred; for 150kHz applications, Kool-mu
(aluminum alloy) and even powdered iron can be
acceptable. If light-load efficiency is unimportant (in
desktop 5V-to-3V applications, for example) then low-
permeability iron-powder cores, such as the
Micrometals type found in Pulse Engineering’s 2.1μH
PE-53680, may be acceptable even at 300kHz. For
high-current applications, shielded core geometries
(such as toroidal or pot core) help keep noise, EMI, and
switching-waveform jitter low.
Current-Sense Resistor Value
The current-sense resistor value is calculated accord-
ing to the worst-case-low current-limit threshold voltage
(from the Electrical Characteristics table) and the peak
inductor current. The continuous-mode peak inductor-
current calculations that follow are also useful for sizing
the switches and specifying the inductor-current satu-
ration ratings. In order to simplify the calculation, I LOAD
over tantalum types, which could cause power-up
surge-current failure, especially when connecting to
robust AC adapters or low-impedance batteries. RMS
input ripple current is determined by the input voltage
and load current, with the worst possible case occur-
ring at V IN = 2 x V OUT :
————————
I RMS = I LOAD x ——————————
V IN
I RMS = I LOAD / 2 when V IN is 2 x V OUT
Output Filter Capacitor Value
The output filter capacitor values are generally deter-
mined by the ESR (effective series resistance) and volt-
age rating requirements rather than actual capacitance
requirements for loop stability. In other words, the low-
ESR electrolytic capacitor that meets the ESR require-
ment usually has more output capacitance than is
required for AC stability. Use only specialized low-ESR
capacitors intended for switching-regulator applications,
such as AVX TPS, Sprague 595D, Sanyo OS-CON, or
Nichicon PL series. To ensure stability, the capacitor
must meet both minimum capacitance and maximum
ESR values as given in the following equations:
V REF (1 + V OUT / V IN(MIN) )
C F > ––––––––––––––––———–––
V OUT x R SENSE x f
R SENSE x V OUT
R ESR < ————————
V REF
(can be multiplied by 1.5, see note below)
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX797EPE | 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 |
| MAX797EPE+ | 制造商:Maxim Integrated Products 功能描述: |
| MAX797ESE | 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 |
| MAX797ESE/GG8 | 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 |
| MAX797ESE/GG8-T | 制造商:Maxim Integrated Products 功能描述:STEP DOWN CONTROLLER - Tape and Reel |
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