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参数资料
| 型号： | LTC3736-2EUF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO24 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-24 |
| 文件页数： | 6/28页 |
| 文件大小： | 344K |
| 代理商： | LTC3736-2EUF#PBF |
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LTC3736-2
14
37362fb
The typical LTC3736-2 application circuit is shown in
Figure 13. External component selection for each of the
LTC3736-2’s controllers is driven by the load requirement
and begins with the selection of the inductor (L) and the
power MOSFETs (MP and MN).
Power MOSFET Selection
Each of the LTC3736-2’s two controllers requires two
external power MOSFETs: a P-channel MOSFET for the
topside (main) switch and an N-channel MOSFET for the
bottom (synchronous) switch. Important parameters for
the power MOSFETs are the breakdown voltage VBR(DSS),
threshold voltage VGS(TH), on-resistance RDS(ON), reverse
transfer capacitance CRSS, turn-off delay tD(OFF) and the
total gate charge QG.
The gate drive voltage is the input supply voltage. Since
the LTC3736-2 is designed for operation down to low input
voltages, a sublogic level MOSFET (RDS(ON) guaranteed at
VGS = 2.5V) is required for applications that work close to
this voltage. When these MOSFETs are used, make sure that
the input supply to the LTC3736-2 is less than the absolute
maximum MOSFET VGS rating, which is typically 8V.
The P-channel MOSFET’s on-resistance is chosen based on
the required load current. The maximum average output
load current IOUT(MAX) is equal to the peak inductor cur-
rent minus half the peak-to-peak ripple current IRIPPLE.
The LTC3736-2’s current comparator monitors the drain-
to-source voltage VDS of the P-channel MOSFET, which
is sensed between the SENSE+ and SW pins. The peak
inductor current is limited by the current threshold, set by
the voltage on the ITH pin of the current comparator. The
voltage on the ITH pin is internally clamped, which limits
the maximum current sense threshold ΔVSENSE(MAX) to
approximately 240mV when IPRG is oating (167mV when
IPRG is tied low; 345mV when IPRG is tied high).
The output current that the LTC3736-2 can provide is
given by:
I
V
R
I
OUT MAX
SENSE MAX
DS ON
RIPPLE
()
–
=
Δ
2
APPLICATIONS INFORMATION
A reasonable starting point is setting ripple current IRIPPLE
to be 40% of IOUT(MAX). Rearranging the above equation
yields:
R
V
I
DS ON MAX
SENSE MAX
OUT MAX
()(
)
()
=
Δ
5
6
or Duty Cycle < 20%.
However, for operation above 20% duty cycle, slope
compensation has to be taken into consideration to select
the appropriate value of RDS(ON) to provide the required
amount of load current:
RSF
V
I
DS ON MAX
SENSE MAX
OUT MAX
()(
)
()
=
Δ
5
6
where SF is a scale factor whose value is obtained from
the curve in Figure 1.
These must be further derated to take into account the
signicant variation in on-resistance with temperature.
The following equation is a good guide for determin-ing
the required RDS(ON)MAXat25°C(manufacturer’sspecica-
tion), allowing some margin for variations in the LTC3736-2
and external component values:
RSF
V
I
DS ON MAX
SENSE MAX
OUT MAX
()(
)
()
(
.
=
Δ
5
6
09
)) ρT
The
ρT is a normalizing term accounting for the tem-
perature variation in on-resistance, which is typically
about 0.4% / °C, as shown in Figure 4. Junction-to-case
temperature TJC is about 10°C in most applications. For
a maximum ambient temperature of 70°C, using
ρ80°C ~
1.3 in the above equation is a reasonable choice.
The power dissipated in the top and bottom MOSFETs
strongly depends on their respective duty cycles and load
current. When the LTC3736-2 is operating in continuous
mode, the duty cycles for the MOSFETs are:
Top P Channel Duty Cycle
V
Bottom N C
OUT
IN
-
=
h
hannel Duty Cycle
VV
V
IN
OUT
IN
=
–
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3736EGN | 功能描述:IC REG CTRLR BUCK PWM CM 24-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3736EGN#PBF | 功能描述:IC REG CTRLR BUCK 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:PolyPhase® 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 |
| LTC3736EGN#TR | 功能描述:IC REG CTRLR BUCK PWM CM 24-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3736EGN#TRPBF | 功能描述:IC REG CTRLR BUCK 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:PolyPhase® 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3736EGN-1 | 功能描述:IC REG CTRLR BUCK PWM CM 24-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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