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參數(shù)資料
| 型號(hào)： | LTC1143LCS-ADJ |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SO-16 |
| 文件頁(yè)數(shù)： | 14/20頁(yè) |
| 文件大?。?/td> | 372K |
| 代理商： | LTC1143LCS-ADJ |
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14
LTC1143/LTC1143L
LTC1143L-ADJ
APPLICATIO
S I
FOR
ATIO
U
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
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
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
.
W
U
U
200k
100k
SHUTDOWN
R
SD
100pF
R1
50k
R2
V
FB
V
OUT
V
IN
1143 F06
Q
SD
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
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)
=
2
( ) (
)
=
1
2
4 1
3 3 2
.
1 38
0 11
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
I
V
V
V
D
SC AVG
D
OUT
IN
=
( )
)
1
With the 0.05
sense resistor, I
SC(AVG)
= 2A will result,
increasing the 0.4V Schottky diode dissipation to 0.8W.
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
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.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1143 | OCTAL BUS TRANSCEIVER O.C. 20-SO 0 to 70 |
| LTC1143L | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LTC1143LCS | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LTC1144C | Switched-Capacitor Wide Input Range Voltage Converter with Shutdown |
| LTC1144 | OCTAL BUS TRANSCEIVER O.C. 20-SO 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1143LCS-ADJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR) |
| LTC1143LCS-ADJ#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR) |
| LTC1143LCS-ADJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR) |
| LTC1144 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Low Noise Dual Supply |
| LTC1144C | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Switched-Capacitor Wide Input Range Voltage Converter with Shutdown |
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