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参数资料
| 型号： | LTC3731HUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/34页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 73 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 750kHz |
| 占空比： | 98.5% |
| 电源电压： | 4 V ~ 36 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 ~ 140°C |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3731
APPLICATIONS INFORMATION
R SENSE = N
V OUT = 0.6V ? 1 +
availableincaseheightsrangingfrom2mmto4mm.Other
capacitor types include Sanyo POSCAP, Sanyo OS-CON,
Nichicon PL series and Sprague 595D series. Consult the
manufacturers for other specific recommendations.
R SENSE Selection for Output Current
Once the frequency and inductor have been chosen,
R SENSE1, R SENSE2, R SENSE3 are determined based on the
required peak inductor current. The current comparator
has a typical maximum threshold of 75mV/R SENSE and
an input common mode range of SGND to (1.1) ? V CC .
The current comparator threshold sets the peak inductor
current, yielding a maximum average output current I MAX
equal to the peak value less half the peak-to-peak ripple
current, ? I L .
Allowing a margin for variations in the IC and external
component values yields:
50mV
I MAX
The IC works well with values of R SENSE from 0.002Ω
to 0.02Ω.
V CC Decoupling
The V CC pin supplies power not only to the internal
circuits of the controller but also to the top and bottom
gate drivers in the LTC3731 UH package, and therefore
must be bypassed very carefully to ground with a ceramic
capacitor, type X7R or X5R (depending upon the operating
temperature environment) of at least 1μF immediately next
to the IC and preferably an additional 10μF placed very
close to the IC due to the extremely high instantaneous
currents involved. The total capacitance, taking into ac-
count the voltage coefficient of ceramic capacitors, should
be 100 times as large as the total combined gate charge
capacitance of ALL of the MOSFETs being driven. Good
bypassing close to the IC is necessary to supply the high
transient currents required by the MOSFET gate drivers
while keeping the 5V supply quiet enough so as not to
disturb the very small-signal high bandwidth of the cur-
rent comparators.
Topside MOSFET Driver Supply (C B , D B )
External bootstrap capacitors, C B , connected to the
BOOST pins, supply the gate drive voltages for the top-
side MOSFETs. Capacitor C B in the Functional Diagram
is charged though diode D B from V CC when the SW pin
is low. When one of the topside MOSFETs turns on, the
driver places the C B voltage across the gate-source of the
desired MOSFET. This enhances the MOSFET and turns
on the topside switch. The switch node voltage, SW,
rises to V IN and the BOOST pin follows. With the topside
MOSFET on, the boost voltage is above the input supply
(V BOOST = V CC + V IN ). The value of the boost capacitor C B
needs to be 30 to 100 times that of the total gate charge
capacitance of the topside MOSFET(s) as specified on the
manufacturer’s data sheet. The reverse breakdown of D B
must be greater than V IN(MAX).
Differential Amplifier/Output Voltage Programming
The IC has a true remote voltage sense capability. The
sensing connections should be returned from the load,
back to the differential amplifier’s inputs through a com-
mon, tightly coupled pair of PC traces. The differential
amplifier rejects common mode signals capacitively or
inductively radiated into the feedback PC traces as well as
ground loop disturbances. The differential amplifier output
signal is divided down with an external resistive divider
and compared with the internal, precision 0.6V voltage
reference by the error amplifier.
The differential amplifier has an output swing range of 0V
to V CC – 1.2V. The output uses an NPN emitter follower
without any internal pull-down current. A DC resistive load
to ground is required in order to sink current.
The differential amplifier is not recommended for high
output voltage applications. However, if it is used, monitor
the V CC rail with the UVADJ function to turn off the control-
ler before the differential amplifier runs out of headroom.
The output voltage is set by an external resistive divider
according to the following formula:
? R1 ?
?
? R2 ?
3731fc
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3731IG | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 36-Pin SSOP |
| LTC3731IG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3731IG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3731IUH | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 32-Pin QFN EP |
| LTC3731IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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