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| 型号： | LT1619EMS8 |
| 厂商： | Linear Technology |
| 文件页数： | 9/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 8-MSOP |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 500kHz |
| 占空比： | 92% |
| 电源电压： | 1.9 V ~ 18 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 是 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
LT1619
APPLICATIO S I FOR ATIO
Diode
Schottky diodes are recommended for low output voltage
applications because of their low forward voltage. Since
Schottky diodes have negligible stored charge, charge
dumping loss is also reduced. The reverse breakdown
voltage of the diode should exceed the maximum reverse
voltage stress of the topology used. The diode should also
be able to carry the peak diode current with acceptable
foward voltage. For the boost converter in Figure 1, the
peak inductor current is approximately 5A. A Motorola
MBRD835 is used due to its low forward voltage.
tolerance of ± 25% and is temperature stable, develops an
offset voltage at the sense input. The value of R OS required
for non-Burst Mode operation can be obtained with the
expression:
I BIAS R OS ≥ V SENSE(BURST)
where
V SENSE(BURST) = (Burst Mode operation peak switch
current, I D(BURST) ) ? R SENSE
For example, if I BIAS = 120 μ A and V SENSE(BURST) = 10mV:
Lowering Burst Mode Operation Current Limit
The LT1619 automatically enters Burst Mode operation as
R OS ≥
10 mV
120 μ A
= 83 ?
V C voltage falls below V B . The corresponding switch
current is the Burst Mode operation switch current thresh-
old, I D(BURST) .
The effective Burst Mode operation current threshold can
be lowered by adding an offset to the input of the current
sense amplifier so that the switch current appears higher
to the PWM comparator. This has the effect of shifting the
V C operating range above V B . Although Burst Mode opera-
tion is not entirely disabled, the peak switch current before
entering Burst Mode operation is greatly reduced due to
the offset of the current sense amplifier. The peak switch
current is also determined by the current sense amplifier
blanking.
To lower the Burst Mode operation current sense thresh-
old, a resistor R OS is added between the SENSE pin and
the sense resistor R SENSE (Figure 5). The input bias
current I BIAS of the current sense amplifier, which has a
Allowing for 25% and 30% variations in I BAIS and
V SENSE(BURST) respectively:
R OS = (1.25)(1.3)(83 ? )
Choose R OS = 137 ? to completely disable Burst Mode
operation. Lower values of R OS (for example, 50 ? to
100 ? ) can be used to lower the effective Burst Mode
current limit.
The value of the sense resistor is then adjusted to compen-
sate for the reduced full-scale sense voltage.
I BIAS R OS + I L(MAX) R SENSE = 40mV
Filtering Current Sense Signal
In a current mode converter, the current sense circuit
senses the switch current and terminates the switch
conduction. In the LT1619, the current sense amplifier
has a full-scale input voltage range from the ground to the
current limit threshold (53mV). Due to high speed switch-
ing transients and parasitic trace inductances, the current
CURRENT
SENSE
AMPLIFIER
I D
sense signal V SENSE tends to be noisy. If the V SENSE
switching transient is excessive, the current sense ampli-
fier will amplify the spurious transient instead, resulting in
jittery operation. In situations where the internal leading
I BIAS = 120 μ A
5
I BIAS = 120 μ A
edge blanking is inadequate, a lowpass filter (Figure 6)
with corner frequency about 5 times the switching
SENSE
4
GND
R OS
R SENSE
1619 F05
frequency can be used to further attenuate high speed
switching transients. In Figure 6 the lowpass filter R OS and
C S has a corner frequency of:
Figure 5. Lowering Burst Mode Operation Current Limit
1619fa
9
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相关代理商/技术参数 |
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| LT1619EMS8#PBF | 功能描述:IC REG CTRLR PWM CM 8-MSOP 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 |
| LT1619EMS8#TR | 功能描述:IC REG CTRLR PWM CM 8-MSOP 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) |
| LT1619EMS8#TRPBF | 功能描述:IC REG CTRLR PWM CM 8-MSOP 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) |
| LT1619EMS8PBF | 制造商:Linear Technology 功能描述:PWM Controller Current Mode 1.5A MSOP8 |
| LT1619ES8 | 功能描述:IC REG CTRLR PWM CM 8-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) |
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