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参数资料
| 型号： | LTC3789EUFD#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.1 A SWITCHING CONTROLLER, 710 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封装： | 4 X 5 MM, LEAD FREE, PLASTIC, MO-220, QFN-28 |
| 文件页数： | 3/28页 |
| 文件大小： | 486K |
| 代理商： | LTC3789EUFD#PBF |
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LTC3789
11
3789f
operaTion
MAIN CONTROL LOOP
The LTC3789 is a current mode controller that provides an
output voltage above, equal to or below the input voltage.
The LTC proprietary topology and control architecture
employs a current-sensing resistor. The inductor current
is controlled by the voltage on the ITH pin, which is the
output of the error amplifier EA. The VFB pin receives the
voltage feedback signal, which is compared to the internal
reference voltage by the EA. If the input/output current
regulation loop is implemented, the sensed inductor cur-
rent is controlled by either the sensed feedback voltage
or the input/output current.
INTVCC/EXTVCC Power
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTVCC pin.
When the EXTVCC is left open or tied to a voltage less
than 4.5V, an internal 5.5V low dropout (LDO) regulator
supplies INTVCC power from VIN. If EXTVCC is taken above
4.8V, the 5.5V regulator is turned off, and another LDO
regulates INTVCC from EXTVCC. The EXTVCC LDO allows
the INTVCC power to be derived from a high efficiency
external source such as the LTC3789 regulator output.
The absolute maximum voltage on EXTVCC is 14V.
Internal Charge Pump
Each top MOSFET driver is biased from the floating boot-
strap capacitors CA and CB, which are normally recharged
byINTVCCthroughanexternaldiodewhenthetopMOSFET
is turned off. When the LTC3789 operates exclusively in
the buck or boost regions, one of the top MOSFETs is
constantly on. An internal charge pump recharges the
bootstrap capacitor to compensate for the small leakage
current through the bootstrap diode so that the MOSFET
can be kept on. However, if a high leakage diode is used
suchthattheinternalchargepumpcannotprovidesufficient
charges to the external bootstrap capacitor, an internal
UVLO comparator, which constantly monitors the drop
across the capacitor, will sense the (BOOST – SW) voltage
when it is below 3.6V. It will turn off the top MOSFET for
about one-twelfth of the clock period every four cycles to
allow CA or CB to recharge.
Shutdown and Start-Up
The controller can be shut down by pulling the RUN
pin low. When the RUN pin voltage is below 0.5V, the
LTC3789 goes into low quiescent current mode. Releas-
ing RUN allows an internal 1.2A current to pull up the
pin and enable the controller. When RUN is above the
accurate threshold of 1.22V, the internal LDO will power
up the INTVCC. At the same time, a 6A pull-up current
will kick in to provide more RUN pin hysteresis. 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.
The start-up of the controller’s output voltage VOUT is
controlled by the voltage on the SS pin. When the voltage
on the SS pin is less than the 0.8V internal reference, the
LTC3789regulatestheVFBvoltagetotheSSvoltageinstead
of the 0.8V reference. This allows the SS pin to be used
to program soft-start by connecting an external capacitor
from the SS pin to SGND. An internal 3A pull-up current
charges this capacitor, creating a voltage ramp on the SS
pin. As the SS voltage rises linearly from 0V to 0.8V (and
beyond),theoutputvoltageVOUTrisessmoothlyfromzero
to its final value. Alternatively, the SS pin can be used to
cause the start-up of VOUT to track that of another supply.
When RUN is pulled low to disable the controller, or when
INTVCC is below the undervoltage lockout threshold of
3.4V, the SS pin is pulled low by an internal MOSFET. In
undervoltage lockout, the controller is disabled and the
external MOSFETs are held off.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3789IGN#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP 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: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 |
| LTC3789IGN#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP 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: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 |
| LTC3789IUFD#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-QFN 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: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 |
| LTC3789IUFD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 28-QFN 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: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 |
| LTC3789IUFDPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller QFN28EP |
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