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| 型号： | LTC3734EUH#TR |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR DC/DC 1PH HI EFF 32QFN |
| 标准包装： | 2,500 |
| 应用： | 控制器，Intel 移动式 CPU |
| 输入电压： | 4 V ~ 30 V |
| 输出数： | 1 |
| 输出电压： | 0.7 V ~ 1.71 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-QFN 裸露焊盘（5x5） |
| 包装： | 带卷 (TR) |
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LTC3734
APPLICATIONS INFORMATION
t ON ( MIN ) <
R SENSE R3
enoughperiodasdeterminedbythesizeoftheC SS ,the
controller will be shut down until the RUN/SS pin voltage
is recycled. If the overload occurs during start-up, the
time can be approximated by:
t LO1 ≈ (C SS ? 0.7V)/(1.5μA) = 4.6 ? 10 5 (C SS )
If the overload occurs after start-up, the voltage on C SS
will continue charging and will provide additional time
before latching off:
t LO2 ≈ (C SS ? 2V)/(1.5μA) = 1.3 ? 10 6 (C SS )
This built-in overcurrent latchoff can be overridden by
providing a pull-up resistor, R SS , to the RUN/SS pin as
shown in Figure 3. This resistance shortens the soft-start
period and prevents the discharge of the RUN/SS capacitor
during a severe overcurrent and/or short-circuit condition.
When deriving the 5μA current from PV CC as in the figure,
current latchoff is always defeated.
Why should you defeat current latchoff? During the pro-
totyping stage of a design, there may be a problem with
noise pickup or poor layout causing the protection circuit
to latch off the controller. Defeating this feature allows
troubleshooting of the circuit and PC layout. The internal
short-circuit and foldback current limiting still remains
active, thereby protecting the power supply system from
failure. A decision can be made after the design is complete
whether to rely solely on foldback current limiting or to
enable the latchoff feature by removing the pull-up resistor.
The value of the soft-start capacitor C SS may need to be
scaled with output voltage, output capacitance and load
current characteristics. The minimum soft-start capaci-
tance is given by:
C SS > (C OUT )(V OUT )(10 -4 )(R SENSE )
A recommended soft-start capacitor of C SS = 0.1μF will
be sufficient for most applications.
Minimum On-Time Considerations
charge required to turn on the top MOSFET. Low duty
cycle applications may approach this minimum on-time
limit and care should be taken to ensure that:
V OUT
V IN ( f )
If the duty cycle falls below what can be accommodated
by the minimum on-time, the LTC3734 will begin to skip
cycles resulting in variable frequency operation. The output
voltage will continue to be regulated, but the ripple current
and ripple voltage will increase.
The minimum on-time for the LTC3734 is generally less
than 150ns. However, as the peak sense voltage decreases,
the minimum on-time gradually increases. This is of par-
ticular concern in forced continuous applications with low
ripple current at light loads. If the duty cycle drops below
the minimum on-time limit in this situation, a significant
amount of cycle skipping can occur with correspondingly
larger ripple current and ripple voltage.
If an application can operate close to the minimum
on-time limit, an inductor must be chosen that has a low
enough inductance to provide sufficient ripple amplitude
to meet the minimum on-time requirement. As a general
rule, keep the inductor ripple current equal to or greater
than 15% of I OUT(MAX) at V IN(MAX) .
Active Voltage Positioning
Active voltage positioning can be used to minimize peak-to-
peak output voltage excursion under worst-case transient
loading conditions. The open-loop DC gain of the control
loop is reduced depending upon the maximum load step
specifications. Active voltage positioning can easily be
added to the LTC3734. Figure 6 shows the equivalent circuit
for implementing AVP. The load line slope is estimated to be:
AVP ? –35.5 ? ? , (9)
m R AVP
Minimum on-time, t ON(MIN) , is the smallest time duration
that the LTC3734 is capable of turning on the top MOSFET.
It is determined by internal timing delays and the gate
if g m ? R3 > 10 ?
V OUT
0.6V
3734fa
19
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相关代理商/技术参数 |
参数描述 |
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| LTC3735EG | 功能描述:IC CTRLR DC/DC 2PH HI EFF 36SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| LTC3735EG#PBF | 功能描述:IC CTRLR DC/DC 2PH HI EFF 36SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:2,000 系列:- 应用:控制器，DSP 输入电压:4.5 V ~ 25 V 输出数:2 输出电压:最低可调至 1.2V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:30-TFSOP（0.173"，4.40mm 宽） 供应商设备封装:30-TSSOP 包装:带卷 (TR) |
| LTC3735EG#TR | 功能描述:IC CTRLR DC/DC 2PH HI EFF 36SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| LTC3735EG#TRPBF | 功能描述:IC CTRLR DC/DC 2PH HI EFF 36SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| LTC3735EUHF | 功能描述:IC CTRLR DC/DC 2PH HI EFF 38-QFN RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
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