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| 型号： | LTM4608IV#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/26页 |
| 文件大小： | 0K |
| 描述： | IC DC/DC UMODULE 8A 68-LGA |
| 产品培训模块： | Power Module vs. Discrete DC to DC |
| 软件下载： | LTM4608 Spice Model |
| 产品目录绘图： | LTM Series_9x15x2.8 |
| 设计资源： | LTM4608IV#PBF Footprint.bxl |
| 特色产品： | μModule Products |
| 标准包装： | 170 |
| 系列： | µModule® |
| 类型： | 非隔离（POL） |
| 输出数： | 1 |
| 电压 - 输入（最小）： | 2.7V |
| 电压 - 输入（最大）： | 5.5V |
| Voltage - Output 1： | 0.6 ~ 5 V |
| 电流 - 输出（最大）： | 8A |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 68-LGA |
| 尺寸/尺寸： | 0.59" L x 0.35" W x 0.11" H（15.0mm x 9.0mm x 2.8mm） |
| 包装： | 托盘 |
| 工作温度： | -40°C ~ 85°C |
| 效率： | 98% |
| 产品目录页面： | 2711 (CN2011-ZH PDF) |
LTM4608
APPLICATIONS INFORMATION
? D ? ( 1 – D )
I CIN(RMS) =
Withoutconsideringtheinductorcurrentripple,theRMS
current of the input capacitor can be estimated as:
I OUT(MAX)
η %
In the above equation, η % is the estimated efficiency of
the power module. The bulk capacitor can be a switcher-
rated electrolytic aluminum capacitor, polymer capacitor
for bulk input capacitance due to high inductance traces
or leads. If a low inductance plane is used to power the
device, then only one 10μF ceramic is required. The three
internal 10μF ceramics are typically rated for 2A of RMS
ripple current, so the ripple current at the worse case for
8A maximum current is 4A or less.
Output Capacitors
The LTM4608 is designed for low output voltage ripple
noise. The bulk output capacitors defined as C OUT are
chosen with low enough effective series resistance (ESR)
to meet the output voltage ripple and transient require-
ments. C OUT can be a low ESR tantalum capacitor, a low
ESR polymer capacitor or ceramic capacitor. The typical
output capacitance range is from 47μF to 220μF. Additional
output filtering may be required by the system designer,
if further reduction of output ripple or dynamic transient
spikes is desired. Table 3 shows a matrix of different output
voltages and output capacitors to minimize the voltage
droop and overshoot during a 3A/μs transient. The table
optimizes total equivalent ESR and total bulk capacitance
to optimize the transient performance. Stability criteria are
considered in the Table 3 matrix, and the Linear Technology
LTpowerCAD? Design Tool is available for stability analysis.
Multiphase operation will reduce effective output ripple as
a function of the number of phases. Application Note 77
discusses this noise reduction versus output ripple cur-
rent cancellation, but the output capacitance will be more
a function of stability and transient response. The Linear
Technology LTpowerCAD Design Tool will calculate the
output ripple reduction as the number phases implemented
increases by N times.
Burst Mode Operation
The LTM4608 is capable of Burst Mode operation in which
the power MOSFETs operate intermittently based on load
demand, thus saving quiescent current. For applications
where maximizing the efficiency at very light loads is a
high priority, Burst Mode operation should be applied. To
enable Burst Mode operation, simply tie the MODE pin to
V IN . During this operation, the peak current of the inductor
is set to approximately 20% of the maximum peak current
value in normal operation even though the voltage at the
I TH pin indicates a lower value. The voltage at the I TH pin
drops when the inductor’s average current is greater than
the load requirement. As the I TH voltage drops below 0.2V,
the BURST comparator trips, causing the internal sleep
line to go high and turn off both power MOSFETs.
In sleep mode, the internal circuitry is partially turned off,
reducing the quiescent current to about 450μA. The load cur-
rent is now being supplied from the output capacitor. When
the output voltage drops, causing I TH to rise above 0.25V,
the internal sleep line goes low, and the LTM4608 resumes
normal operation. The next oscillator cycle will turn on the
top power MOSFET and the switching cycle repeats.
Pulse-Skipping Mode Operation
In applications where low output ripple and high efficiency
at intermediate currents are desired, pulse-skipping mode
should be used. Pulse-skipping operation allows the
LTM4608 to skip cycles at low output loads, thus increasing
efficiency by reducing switching loss. Floating the MODE
pin or tying it to V IN /2 enables pulse-skipping operation.
This allows discontinuous conduction mode (DCM) opera-
tion down to near the limit defined by the chip’s minimum
on-time (about 100ns). Below this output current level,
the converter will begin to skip cycles in order to main-
tain output regulation. Increasing the output load current
slightly, above the minimum required for discontinuous
conduction mode, allows constant frequency PWM.
4608fd
11
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相关代理商/技术参数 |
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| LTM4608V | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low VIN, 8A DC/DC μModuleTM with Tracking, Margining, and Frequency Synchronization |
| LTM4609 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency, Synchronous, 4-Switch Buck-Boost Controller |
| LTM4609_12 | 制造商:LINER 制造商全称:Linear Technology 功能描述:36VIN, 34VOUT High Efficiency Buck-Boost DC/DC |
| LTM4609EV | 制造商:LINER 制造商全称:Linear Technology 功能描述:36VIN, 34VOUT High Effi ciency Buck-Boost DC/DC μModule |
| LTM4609EV#PBF | 功能描述:IC UMODULE BUCK-BOOST 141-LGA RoHS:是 类别:电源 - 板载 >> DC DC Converters 系列:µModule® 设计资源:VI-200, VI-J00 Design Guide, Appl Manual 标准包装:1 系列:* 类型:隔离 输出数:1 电压 - 输入（最小）:66V 电压 - 输入（最大）:160V Voltage - Output 1:12V Voltage - Output 2:- Voltage - Output 3:- 电流 - 输出（最大）:* 电源（瓦） - 制造商系列:50W 电压 - 隔离:* 特点:* 安装类型:通孔 封装/外壳:9-FinMod 尺寸/尺寸:4.60" L x 1.86" W x 0.79" H（116.8mm x 47.2mm x 20.1mm） 包装:散装 工作温度:-25°C ~ 85°C 效率:* 电源（瓦特）- 最大:* |
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