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参数资料
| 型号： | LT3507AIUHF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PQCC38 |
| 封装： | 5 X 7 MM, LEAD FREE, PLASTIC, QFN-38 |
| 文件页数： | 28/28页 |
| 文件大小： | 372K |
| 代理商： | LT3507AIUHF#PBF |
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LT3507A
9
3507af
OPERATION
The LT3507A contains three independent, constant fre-
quency, current mode, switching regulators with internal
power switches plus a low dropout linear regulator. The
three regulators share common circuitry including input
source, voltage reference and oscillator, but are otherwise
independent. Operation can be best understood by refer-
ring to the Block Diagram (Figure 1).
If the RUN pins are tied to ground, the LT3507A is shut
down and draws <1A from the input source tied to VIN1. If
any of the RUN pins are driven above 1V, the internal bias
circuits turn on, including the internal regulator, reference,
and master oscillator. Each switching regulator will only
begin to operate when its corresponding RUN pin reaches
>1.25V.Themasteroscillatorgeneratesthreeclocksignals,
with the signal for channel 1 out of phase by 180°.
The three switchers are current mode regulators. Instead
of directly modulating the duty cycle of the power switch,
the feedback loop controls the peak current in the switch
duringeachcycle.Comparedtovoltagemodecontrol,cur-
rent mode control improves loop dynamics and provides
cycle-by-cycle current limit.
The Block Diagram shows only one of the three step-down
switching regulators. A pulse from the slave oscillator
sets the RS flip-flop and turns on the internal NPN bipo-
lar power switch. Current in the switch and the external
inductor begins to increase. When this current exceeds a
level determined by the voltage at VC, current comparator
C1 resets the flip-flop, turning off the switch. The current
in the inductor flows through the external Schottky diode
and begins to decrease. The cycle begins again at the next
pulse from the oscillator. In this way, the voltage on the
VC pin controls the current through the inductor to the
output. The internal error amplifier regulates the output
voltage by continually adjusting the VC pin voltage. The
threshold for switching on the VC pin is >1V and an active
clamp of 1.8V limits the output current.
Each switcher contains an extra, independent oscillator to
perform frequency foldback during overload conditions.
Thisslaveoscillatorisnormallysynchronizedtothemaster
oscillator. A comparator senses when VFB is less than 50%
of its regulated value and switches the regulator from the
masteroscillatortoaslowerslaveoscillator.VFBislessthan
50% of its regulated value during start-up, short-circuit
and overload conditions. Frequency foldback helps limit
switch current under these conditions.
The TRK/SS pins override the 0.8V reference for the FB
pins when the TRK/SS pins are below 0.8V. This allows
eithercoincidentorratiometricsupplytrackingonstart-up
as well as a soft-start capability.
The switch drivers operate either from VIN or from the
BOOST pin. An external capacitor and diode are used to
generate a voltage at the BOOST pin that is higher than
the input supply. This allows the driver to saturate the
internal bipolar NPN power switch for efficient operation.
TheBIASpinallowstheinternalcircuitrytodrawitscurrent
from a lower voltage supply than the input, also reducing
power dissipation and increasing efficiency. If the voltage
on the BIAS pin falls below 3V, then its quiescent current
will flow from VIN.
ApowergoodcomparatortripswhentheFBpinisat90%of
itsregulatedvalue.ThePGOODoutputisanopen-collector
transistor that is off when the output is in regulation, al-
lowing an external resistor to pull the PGOOD pin high.
Power good is valid when the LT3507A is enabled and VIN
is within normal operating range.
The LDO regulator uses an external NPN pass transistor to
form a linear regulator. The loop is internally compensated
to be stable with a load capacitance of 2.2F or greater.
The LDO is disabled when all three of the RUN pins are low.
The overvoltage and undervoltage detection shuts down
the LT3507A if the input voltage goes above or below re-
sistor programmable thresholds. The hysteresis of these
detectors is also resistor programmable.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3507EUHF#2ESPBF | 制造商:Linear Technology 功能描述:TRIPLE MONOLITHIC STEP-DOWN REGULATOR WITH LDO |
| LT3507EUHF#PBF | 功能描述:IC REG QD BUCK/LINEAR 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT3507EUHF#TRPBF | 功能描述:IC REG QD BUCK/LINEAR 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT3507EUHFPBF | 制造商:Linear Technology 功能描述:Step Down Regulator with LDO |
| LT3507EUHF-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Monolithic Step-Down Regulator with LDO |
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