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| 型号： | MAX1847EEE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK INV CM 16QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 345kHz |
| 占空比： | 98% |
| 电源电压： | 3 V ~ 16.5 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1410 (CN2011-ZH PDF) |
High-Efficiency, Current-Mode,
Inverting PWM Controller
tance as possible. For continuous inductor current, the
power loss in the inductor resistance (P LR ) is approxi-
mated by:
Power MOSFET Selection
The MAX1846/MAX1847 drive a wide variety of P-chan-
nel power MOSFETs (PFETs). The best performance,
? ?
P LR L x ?
I LOAD
?
~ R
? I ? D MAX ?
2
especially with input voltages below 5V, is achieved
with low-threshold PFETs that specify on-resistance
with a gate-to-source voltage (V GS ) of 2.7V or less.
When selecting a PFET, key parameters include:
( )
L MIN = ? V IN ( MIN ) x R CS / M S ?
( ) ( )
? 2 xD ?
MAX MAX ?
? ?
?
where R L is the inductor series resistance.
Once the peak inductor current is calculated, the cur-
rent sense resistor, R CS , is determined by:
R CS = 85mV / I LPEAK
For high peak inductor currents (>1A), Kelvin-sensing
connections should be used to connect CS and PGND
to R CS . Connect PGND and GND together at the
ground side of R CS . A lowpass filter between R CS and
CS may be required to prevent switching noise from
tripping the current-sense comparator at heavy loads.
Connect a 100 ? resistor between CS and the high side
of R CS , and connect a 1000pF capacitor between CS
and GND.
Checking Slope-Compensation Stability
In a current-mode regulator, the cycle-by-cycle stability
is dependent on slope compensation to prevent sub-
harmonic oscillation at duty cycles greater than 50%.
For the MAX1846/MAX1847, the internal slope compen-
sation is optimized for a minimum inductor value (L MIN )
with respect to duty cycle. For duty cycles greater then
50%, check stability by calculating LMIN using the fol-
lowing equation:
?? ??
x ? 1 / 1 ? D
where V IN(MIN) is the minimum expected input voltage,
M s is the Slope Compensation Ramp (41 mV/μs) and
D MAX is the maximum expected duty cycle. If L MIN is
larger than L, increase the value of L to the next stan-
dard value that is larger than L MIN to ensure slope
compensation stability.
Choosing the Inductor Core
Choosing the most cost-effective inductor usually
requires optimizing the field and flux with size. With
higher output voltages the inductor may require many
turns, and this can drive the cost up. Choosing an
inductor value at L MIN can provide a good solution if
discontinuous inductor current can be tolerated.
Powdered iron cores can provide the most economical
solution but are larger in size than ferrite.
? Total gate charge (Q G )
? Reverse transfer capacitance (C RSS )
? On-resistance (R DS(ON) )
? Maximum drain-to-source voltage (V DS(MAX) )
? Minimum threshold voltage (V TH(MIN) )
At high-switching rates, dynamic characteristics (para-
meters 1 and 2 above) that predict switching losses
may have more impact on efficiency than R DS(ON ),
which predicts DC losses. Q G includes all capacitance
associated with charging the gate. In addition, this
parameter helps predict the current needed to drive the
gate at the selected operating frequency. The power
MOSFET in an inverting converter must have a high
enough voltage rating to handle the input voltage plus
the magnitude of the output voltage and any spikes
induced by leakage inductance and ringing.
An RC snubber circuit across the drain to ground might
be required to reduce the peak ringing and noise.
Choose R DS(ON)(MAX) specified at V GS < V IN(MIN) to be
one to two times R CS . Verify that V IN(MAX) < V GS(MAX)
and V DS(MAX) > V IN(MAX) - V OUT + V D . Choose the rise-
and fall-times (t R , t F ) to be less than 50ns.
Output Capacitor Selection
The output capacitor (C OUT ) does all the filtering in an
inverting converter. The output ripple is created by the
variations in the charge stored in the output capacitor
with each pulse and the voltage drop across the
capacitor’s equivalent series resistance (ESR) caused
by the current into and out of the capacitor. There are
two properties of the output capacitor that affect ripple
voltage: the capacitance value, and the capacitor’s
ESR. The output ripple due to the output capacitor’s
value is given by:
V RIPPLE-C = (I LOAD D MAX T OSC ) / C OUT
The output ripple due to the output capacitor’s ESR is
given by:
V RIPPLE-R = I LPP R ESR
These two ripple voltages are additive and the total out-
put ripple is:
V RIPPLE-T = V RIPPLE-C + V RIPPLE-R
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1847EEE+ | 功能描述:电流型 PWM 控制器 Current-Mode Invert PWM Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1847EEE+ | 制造商:Maxim Integrated Products 功能描述:PWM CONTROLLER ((NW)) |
| MAX1847EEE+T | 功能描述:电流型 PWM 控制器 Current-Mode Invert PWM Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1847EEE-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1848EKA | 制造商:Maxim Integrated Products 功能描述:HIGH-EFFICIENCY UNIFORM-BRIGHTNESS - Rail/Tube |
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