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| 型号： | LTC3788IUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 32-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 38 V |
| 降压： | 无 |
| 升压： | 是 |
| 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： | 32-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3788
OPERATION
R SENSE =
I MAX +
MOSFETturnson.Therearetwoconsiderationstokeep
the BOOST supply at the required bias level. During
start-up, if the bottom MOSFET is not turned on within
100μs after UVLO goes low, the bottom MOSFET will be
forced to turn on for ~400ns. This forced refresh gener-
ates enough BOOST-SW voltage to allow the top MOSFET
ready to be fully enhanced instead of waiting for the initial
APPLICATIONS INFORMATION
The Typical Application on the first page is a basic
LTC3788 application circuit. LTC3788 can be configured
to use either inductor DCR (DC resistance) sensing or a
discrete sense resistor (R SENSE ) for current sensing. The
choice between the two current sensing schemes is largely
a design trade-off between cost, power consumption and
accuracy. DCR sensing is becoming popular because it
does not require current sensing resistors and is more
power-efficient, especially in high current applications.
However, current sensing resistors provide the most
accurate current limits for the controller. Other external
component selection is driven by the load requirement,
and begins with the selection of R SENSE (if R SENSE is used)
and inductor value. Next, the power MOSFETs are selected.
Finally, input and output capacitors are selected.
SENSE + and SENSE – Pins
The SENSE + and SENSE – pins are the inputs to the cur-
rent comparators. The common mode input voltage range
of the current comparators is 2.5V to 38V. The current
sense resistor is normally placed at the input of the boost
controller in series with the inductor.
The SENSE + pin also provides power to the current
comparator. It draws ~200μA during normal operation.
There is a small base current of less than 1μA that flows
into the SENSE – pin. The high impedance SENSE – input
to the current comparators allow accurate DCR sensing.
Filter components mutual to the sense lines should be
placed close to the LTC3788, and the sense lines should
run close together to a Kelvin connection underneath the
current sense element (shown in Figure 1). Sensing cur-
few cycles to charge up. There is also an internal charge
pump that keeps the required bias on BOOST. The charge
pump always operates in both forced continuous mode
and pulse-skipping mode. In Burst Mode operation, the
charge pump is turned off during sleep and enabled when
the chip wakes up. The internal charge pump can normally
supply a charging current of 55μA.
rent elsewhere can effectively add parasitic inductance
and capacitance to the current sense element, degrading
the information at the sense terminals and making the
programmed current limit unpredictable. If DCR sensing
is used (Figure 2b), sense resistor R1 should be placed
close to the switching node, to prevent noise from coupling
into sensitive small-signal nodes.
TO SENSE FILTER,
NEXT TO THE CONTROLLER
V IN
INDUCTOR OR R SENSE 3788 F01
Figure 1. Sense Lines Placement with
Inductor or Sense Resistor
Sense Resistor Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 2a. R SENSE is chosen based on the required
output current.
The current comparator has a maximum threshold
V SENSE(MAX) . When the ILIM pin is grounded, floating or
tied to INTV CC , the maximum threshold is set to 50mV,
75mV or 100mV, respectively. The current comparator
threshold sets the peak of the 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 .
To calculate the sense resistor value, use the equation:
V SENSE(MAX)
? I L
2
3788fc
15
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相关代理商/技术参数 |
参数描述 |
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| LTC3789EGN#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 |
| LTC3789EGN#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 600kHz SSOP28 |
| LTC3789EGN#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 |
| LTC3789EUFD#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 |
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