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參數(shù)資料
| 型號： | LT1339CSW |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Octal Buffers/Drivers With 3-State Outputs 20-SOIC 0 to 70 |
| 中文描述： | SWITCHING CONTROLLER, 150 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | 0.300 INCH, PLASTIC, SO-20 |
| 文件頁數(shù)： | 10/20頁 |
| 文件大?。?/td> | 415K |
| 代理商： | LT1339CSW |
10
LT1339
APPLICATIO
S I
FOR
ATIO
U
R
SENSE
Selection for Output Current
R
SENSE
generates a voltage that is proportional to the
inductor current for use by the LT1339 current sense
amplifier. The value of R
SENSE
is based on the required
load current. The average current limit function has a
typical threshold of 120mV/R
SENSE
, or:
R
SENSE
= 120mV/I
LIMIT
Operation with V
SENSE
common mode voltage below 4.5V
may slightly degrade current limit accuracy. See Average
Current Limit Threshold Tolerance vs Common Mode
Voltage curve in the Typical Performance Characteristics
section for more information.
W
U
U
Output Voltage Programming
Output voltage is programmed through a resistor feed-
back network to V
FB
(Pin 9) on the LT1339. This pin is the
inverting input of the error amplifier, which is internally
referenced to 1.25V. The divider is ratioed to provide
1.25V at the V
FB
pin when the output is at its desired value.
The output voltage is thus set following the relation:
V
OUT
= 1.25(1 + R2/R1)
when an external resistor divider is connected to the
output as shown in Figure 1.
the minimum off-time of the PWM controller. This limits
maximum duty cycle (DC
MAX
) to:
DC
MAX
= 1 – (t
DISCH
)(f
O
)
This relation corresponds to the minimum value of the
timing resistor (R
CT
), which can be determined according
to the following relation (R
CT
vs DC
MAX
graph appears in
the Typical Performance Characteristics section):
R
CT(MIN)
≈
[(0.8)(10
–3
)(1 – DC
MAX
)]
–1
Values for R
CT
> 15k yield maximum duty cycles above
90%. Given a timing resistor value, the value of the timing
capacitor (C
CT
) can then be determined for desired oper-
ating frequency (f
O
) using the relation:
C
f
R
(
R
CT
O
CT
CT
≈
(
)
(
)
)
+
( )
(
)
1
100 10
/1 85
1.
2 5 10
.
3 375
.
9
3
/
/
A plot of Operating Frequency vs R
CT
and C
CT
is shown in
Figure 2. Typical 100kHz operational values are C
CT
=
1000pF and R
CT
= 16.9k.
R1
R2
V
OUT
1339 F01
V
FB
SGND
LT1339
9
8
Figure 1. Programming LT1339 Output Voltage
If high value feedback resistors are used, the input bias
current of the V
FB
pin (1
μ
A maximum) could cause a slight
increase in output voltage. A Thevenin resistance at the
V
FB
pin of <5k is recommended.
Oscillator Components R
CT
and C
CT
The LT1339 oscillator creates a modified sawtooth wave
at its timing node (CT) with a slow charge, rapid discharge
characteristic. The rapid discharge time corresponds to
Figure 2. Oscillator Frequency vs R
CT
, C
CT
Average Current Limit
The average current limit function is implemented using
an external capacitor (C
AVG
) connected from I
AVG
to SGND
that forms a single pole integrator with the 50k
output
TIMING RESISTOR (k
)
0
O
15
25
LT1339 F02
5
10
20
160
140
120
100
80
60
40
20
0
30
C
CT
= 3.3nF
C
CT
= 2.2nF
C
CT
= 1.5nF
C
CT
= 1.0nF
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1339I | Octal Buffers/Drivers With 3-State Outputs 20-SOIC 0 to 70 |
| LT1339IN | Octal Buffers/Drivers With 3-State Outputs 20-PDIP 0 to 70 |
| LT1339ISW | High Power Synchronous DC/DC Controller |
| LT1341 | 5V RS232 Transceiver with One Receiver Active in Shutdown |
| LT1341C | Octal Buffers/Drivers With 3-State Outputs 20-PDIP 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1339CSW#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
| LT1339CSW#TR | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1339CSW#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1339CSWPBF | 制造商:Linear Technology 功能描述:DC-DC Controller High Power Synch. SO20W |
| LT1339CSWTRPBF | 制造商:Linear Technology 功能描述: |
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