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| 型号： | LT1339CSW#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 20-SOIC |
| 标准包装： | 1,000 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 150kHz |
| 占空比： | 90% |
| 电源电压： | 最高 60V |
| 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： | 0°C ~ 70°C |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 包装： | 带卷 (TR) |
LT1339
APPLICATIO N S I N FOR M ATIO N
(
)
S X ≥ ? IN ? 2 DC ? 1
(
)
L MIN = ? IN ? 2 DC ? 1
? R SENSE ?
( 2500 )( f O )
( R EQ )( R SENSE )
( V IN )( R SENSE ) ( 2 DC ? 1 )
( )( f O )
Subharmonicoscillationscanbeeliminatedbyaugment-
ing the increasing ripple current slope (S1) in the control
loop. This is accomplished by adding an artificial ramp on
the inductor current waveform internal to the IC (with a
slope S X ) as shown in Figure 5b. If the sum of the slopes
S1 + S X is greater than S2, the condition for subharmonic
oscillation no longer exists.
For a buck converter, the required additional current wave-
form slope, or “Slope Compensation,” follows the relation:
? V ?
? L ?
For duty cycles less than 50% (DC < 0.5), S X is negative
and is not required. For duty cycles greater than 50%, S X
takes on values dependent on S1 and duty cycle. This leads
to a minimum inductance requirement for a given V IN and
duty cycle of:
? V ?
? S X ?
The LT1339 contains an internal S X slope compensation
ramp that has an equivalent current referred value of:
? f O ?
0.084 ? ? Amp/s
where f O is oscillator frequency. This yields a minimum
inductance requirement of:
L MIN ≥
0 . 084
A down side of slope compensation is that, since the IC servo
loop senses an increase in perceived inductor current, the
internal current limit functions are affected such that the
maximum current capability of a regulator is reduced by the
same amount as the effective current referred slope com-
pensation. The LT1339, however, uses a current limit
scheme that is independent of slope compensation effects
(average current limit). This provides operation at any duty
cycle with no reduction in current sourcing capability,
provided ripple current peak amplitude is less than 15% of
the current limit value. For example, if the supply is set up
to current limit at 10A, as long as the peak inductor current
is less than 11.5A, duty cycles up to 90% can be achieved
without compromising the average current limit value.
If an inductor smaller than the minimum required for
internal slope compensation (calculated above as L MIN ) is
desired, additional slope compensation is required. The
LT1339 provides this capability through the SL/ADJ pin.
This feature is implemented by referencing this pin via a
resistor divider from the 5V REF pin to ground. The addi-
tional slope compensation will be affected at the point in
the oscillator waveform (at pin CT) corresponding to the
voltage set by the resistor divider. Additional slope com-
pensation can be calculated using the relation:
S XADD = Amp/s
where R EQ is the effective resistance of the resistor divider.
Actual compensation will be somewhat greater due to in-
ternal curvature correction circuitry that imposes an expo-
nential increase in the slope compensation waveform,
1.45
1.40
1.35
1.30
I 2
? I
T1
S1 + S X
1.25
1.20
I 1
S1
S2
S1
S2
1.15
0
OSCILLATOR
PERIOD
a
TIME
b
0
1339 ? F05
1.10
0
0.1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
DUTY CYCLE (DC)
LT1339 ? F06
Figure 5. Inductor Current at DC > 50% and
Slope Compensation Adjusted Signal
Figure 6. Maximum Ripple Current (Normalized)
vs Duty Cycle for Average Current Limit
sn1339 1339fas
13
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相关代理商/技术参数 |
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| LT1339I | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power Synchronous DC/DC Controller |
| LT1339IN | 功能描述:IC REG CTRLR BST PWM CM 20-DIP 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: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 |
| LT1339IN#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-DIP 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 |
| LT1339ISW | 功能描述:IC REG CTRLR BST PWM CM 20-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: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 |
| LT1339ISW#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-SOIC 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 |
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