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参数资料
| 型号： | LTC3778EF#TR |
| 厂商： | Linear Technology |
| 文件页数： | 10/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 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 ~ 85°C |
| 封装/外壳： | 20-TSSOP（0.173"，4.40mm 宽） |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC3778EFTR |
LTC3778
APPLICATIO S I FOR ATIO
The basic LTC3778 application circuit is shown in
Figure 1. External component selection is primarily de-
termined by the maximum load current and begins with
the selection of the sense resistance and power MOSFET
switches. The LTC3778 can use either a sense resistor or
the on-resistance of the synchronous power MOSFET for
determining the inductor current. The desired amount of
ripple current and operating frequency largely deter-
mines the inductor value. Finally, C IN is selected for its
ability to handle the large RMS current into the converter
and C OUT is chosen with low enough ESR to meet the
output voltage ripple and transient specification.
Maximum Sense Voltage and V RNG Pin
Inductor current is determined by measuring the voltage
across a sense resistance that appears between the SENSE –
and SENSE + pins. The maximum sense voltage is set by
the voltage applied to the V RNG pin and is equal to
approximately (0.133)V RNG . The current mode control
loop will not allow the inductor current valleys to exceed
(0.133)V RNG /R SENSE . In practice, one should allow some
margin for variations in the LTC3778 and external compo-
nent values and a good guide for selecting the sense
resistance is:
Connecting the SENSE + and SENSE – Pins
The LTC3778 can be used with or without a sense resistor.
When using a sense resistor, it is placed between the
source of the bottom MOSFET, M2, and PGND. Connect
the SENSE + and SENSE – pins to the top and bottom of the
sense resistor. Using a sense resistor provides a well
defined current limit, but adds cost and reduces efficiency.
Alternatively, one can eliminate the sense resistor and use
the bottom MOSFET as the current sense element by
simply connecting the SENSE + pin to the SW pin and
SENSE – pin to PGND. This improves efficiency, but one
must carefully choose the MOSFET on-resistance as dis-
cussed below.
Power MOSFET Selection
The LTC3778 requires two external N-channel power
MOSFETs, one for the top (main) switch and one for the
bottom (synchronous) switch. Important parameters for
the power MOSFETs are the breakdown voltage V (BR)DSS ,
threshold voltage V (GS)TH , on-resistance R DS(ON) , reverse
transfer capacitance C RSS and maximum current I DS(MAX) .
The gate drive voltage is set by the 5V INTV CC and DRV CC
supplies. Consequently, logic-level threshold MOSFETs
must be used in LTC3778 applications. If the input voltage
R SENSE =
V RNG
10 ? I OUT ( MAX )
or DRV CC voltage is expected to drop below 5V, then sub-
logic level threshold MOSFETs should be considered.
An external resistive divider from INTV CC can be used to
set the voltage of the V RNG pin between 0.5V and 2V
resulting in nominal sense voltages of 50mV to 200mV.
Additionally, the V RNG pin can be tied to SGND or INTV CC
in which case the nominal sense voltage defaults to 70mV
or 140mV, respectively. The maximum allowed sense
When the bottom MOSFET is used as the current sense
element, particular attention must be paid to its on-
resistance. MOSFET on-resistance is typically specified
with a maximum value R DS(ON)(MAX) at 25 ° C. In this case,
additional margin is required to accommodate the rise in
MOSFET on-resistance with temperature:
voltage is about 1.33 times this nominal value.
R DS ( ON )( MAX ) =
R SENSE
ρ T
3778f
10
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| LTC3780EG | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP |
| LTC3780EG#PBF | 功能描述:IC REG CTRLR BST PWM CM 24-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3780EG#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP T/R |
| LTC3780EG#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 24-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 |
| LTC3780EGPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller SSOP24 |
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