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参数资料
| 型号： | LTC3833IUDC#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20-QFN |
| 标准包装： | 91 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 2.2MHz |
| 电源电压： | 4.5 V ~ 38 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： | 20-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3833
OPERATION (Refer to Functional Diagram)
The voltage on the ITH pin sets the I CMP valley threshold
point. The error amplifier, EA, adjusts this ITH voltage
by comparing the differential feedback signal, V OSNS+ ?
V OSNS– , to a 0.6V internal reference voltage. Consequently,
the LTC3833 regulates the output voltage by forcing the
differential feedback voltage to be equal to the 0.6V internal
reference. The difference amplifier, DA, converts the dif-
ferential feedback signal to a single-ended input for the
EA. If the load current increases, it causes a drop in the
differential feedback voltage relative to the reference. The
EA forces ITH voltage to rise until the average inductor
current again matches the load current.
Differential Output Sensing
The output voltage is resistively divided externally to create
a feedback voltage for the controller. The internal difference
amplifier, DA, senses this feedback voltage along with the
output’s remote ground reference to create a differential
feedback voltage. This scheme overcomes any ground
offsets between local ground and remote output ground,
resulting in a more accurate output voltage. The LTC3833
allows for remote output ground deviations as much as
±500mV with respect to local ground.
INTV CC /EXTV CC Power
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTV CC pin. Power
on the INTV CC pin is derived in two ways: if the EXTV CC
pin is below 4.6V, then an internal 5.3V low dropout linear
regulator, LDO, supplies INTV CC power from V IN ; if the
EXTV CC pin is tied to an external source larger than 4.6V,
then the LDO is shut down and an internal switch shorts
the EXTV CC pin to the INTV CC pin, thereby powering the
INTV CC pin with the external source and helping to increase
overall efficiency and decrease internal self heating through
power dissipated in the LDO. This external power source
could be the output of the step-down switching regulator
itself if the output is programmed to higher than 4.6V.
The top MOSFET driver is biased from the floating boot-
strap capacitor, C B , which normally recharges during
each off cycle through an external Schottky diode when
the top MOSFET turns off. If the V IN voltage is low and
INTV CC drops below 3.65V, undervoltage lockout circuitry
disables the external MOSFET driver and prevents the
power switches from turning on.
Shutdown and Start-Up
The LTC3833 can be shut down using the RUN pin. Pulling
this pin below 1.2V prevents the controller from switch-
ing, and less than 0.75V disables most of the internal bias
circuitry, including the INTV CC regulator. When RUN is less
than 0.75V, the shutdown I Q is about 15μA. Pulling the RUN
pin between 0.75V and 1.2V enables the controller into a
standby mode where all internal circuitry is powered-up
but the external MOSFET driver is disabled. The standby I Q
is about 2mA. Releasing the RUN pin from ground allows
an internal 1.3μA current to pull the pin above 1.2V and
fully enable the controller including the external MOSFET
driver. Alternatively, the RUN pin may be externally pulled
up or driven directly by logic. Be careful not to exceed the
absolute maximum rating of 6V on this pin. When pulled up
by a resistor to an external voltage, the RUN pin will sink
up to 35μA of current before reaching 6V. If the external
voltage is above 6V (e.g., V IN ), select a large enough resis-
tor value so that the voltage on RUN will not exceed 6V.
The start-up of the controller’s output voltage, V OUT , is
controlled by the voltage on the TRACK/SS pin. When
the voltage on the TRACK/SS pin is less than the 0.6V
internal reference, the LTC3833 regulates the differential
feedback voltage to the TRACK/SS voltage instead of the
0.6V reference. This allows the TRACK/SS pin to be used
for programming a ramp-up time for V OUT by connecting
an external capacitor from the TRACK/SS pin to SGND. An
internal 1μA pull-up current charges this capacitor, creating
a voltage ramp on the TRACK/SS pin. As the TRACK/SS
voltage rises from 0V to 0.6V (and beyond), the LTC3833
forces the output voltage, V OUT , to ramp up smoothly to
its final value. Alternatively, the TRACK/SS pin can be used
to track the start-up of V OUT to another external supply
as in a master slave configuration. Typically, this requires
connecting a resistor divider from the master supply to
the TRACK/SS pin (see Soft-Start and Tracking).
3833f
11
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| LTC3834EDHC-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
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