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| 型号： | LTC1143CS |
| 厂商： | Linear Technology |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 400kHz |
| 占空比： | 100% |
| 电源电压： | 3.5 V ~ 16 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： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 其它名称： | LTC1143CSW LTC1143CSW-ND |
LTC1143/LTC1143L
LTC1143L-ADJ
APPLICATIO N S I N FOR M ATIO N
The LTC1143L-ADJ outputs can be turned off in one of two
ways: 1) by placing a power MOSFET switch in the V IN line
δ P = 0.005(100 – 25) = 0.38. The maximum R DS(ON) for
each MOSFET can now be calculated:
P - Ch R DS(ON) = ?
( ) ?? = 0 . 11 ?
( ) ( ) ? ?
3 . 3 2 1 . 38
to the entire regulator or 2) by pulling the V FB pin over
1.4V, which trips comparator V and forces P-DRIVE high
(see Functional Diagram). V FB can be pulled high with a
small current, but any circuitry used to shut down the
LTC1143L-ADJ in this manner must minimize V FB lead
?
1 ?
2 ?
?
41
2
?
length to prevent noise coupling during normal operation.
In the Figure 6 circuit, taking SHUTDOWN high turns on
PNP Q SD that sources a current into V FB . To shut down
properly, RSD must be chosen to pull V FB above 1.4V with
V OUT at 0V and minimum V IN . Note that this technique
depends on the load resistance to prevent V OUT from
floating up due to the current flowing into V FB .
Allowing for V IN being slightly below the V GS used to
specify R DS(ON) , this requirement can be met by half of
a Siliconix Si4953DY, Fairchild NDS8947 or similar
SO-8 dual P-channel MOSFET.
The most stringent requirement for the Schottky diode is
with V OUT = 0V (i.e. short circuit). During a continuous short
circuit, the worst-case Schottky diode dissipation rises to:
( )
P D SC ( AVG ) V D ? 1 ? OUT ?
V FB
V OUT
R2
Q SD
V IN
R SD
200k
100k
? V ?
= I
? V IN ?
With the 0.05 ? sense resistor, I SC(AVG) = 2A will result,
increasing the 0.4V Schottky diode dissipation to 0.8W.
100pF
R1
50k
SHUTDOWN
C IN will require an RMS current rating of at least 1A at
temperature and C OUT will require an ESR of 0.05 ? for
1143 F06
Figure 6. Local V FB Pull-Up Shuts Down LTC1143L-ADJ
Design Example
As a design example, assume V IN = 12V(nominal), V OUT =
3.3V, I MAX = 2A and ? = 200kHz. R SENSE , C T and L can
immediately be calculated:
R SENSE = 100mV/2 = 0.05 ?
t OFF = (1/200kHz)[1 – (3.3/12)] = 3.63 μ s
C T = 3.63 μ s/(1.3 × 10 4 ) = 280pF (use 300pF)
L MIN = 5.1(10 5 )(0.05 ?) (300pF) 3.3V = 25 μ H
Assume a dual P-channel power MOSFET is to be
used and dissipation is to be limited to 1W total at
worst-case lowest V IN = 4V. If T A = 50 ° C and the
thermal resistance of the MOSFET package is 50 ° C/W,
then the junction temperature will be 100 ° C and
14
optimum efficiency.
Troubleshooting Hints
Since efficiency is critical to LTC1143 series applications
it is very important to verify that the circuit is functioning
correctly in both continuous and Burst Mode operation.
The waveform to monitor is the voltage on the timing
capacitor Pins 6 and 14.
In continuous mode (I LOAD > I BURST ) the voltage on the C T
pin should be a sawtooth with a 0.9V P-P swing. This
voltage should never dip below 2V as shown in Figure 7a.
When load currents are low (I LOAD < I BURST ) Burst Mode
operation occurs. The voltage on the C T pin now falls to
ground for periods of time as shown in Figure 7b.
If Pin 6 or Pin 14 is observed falling to ground at high
output currents, it indicates poor decoupling or improper
grounding. Refer to the Board Layout Checklist.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1143CS#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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:2,500 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) |
| LTC1143CS#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 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) |
| LTC1143CS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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:2,500 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) |
| LTC1143L | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual High Efficiency SO-16 Step-Down Switching Regulator Controllers |
| LTC1143L-ADJ | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual High Efficiency SO-16 Step-Down Switching Regulator Controllers |
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