参数资料
型号: LT1307CMS8
厂商: Linear Technology
文件页数: 10/20页
文件大小: 0K
描述: IC REG BOOST 3.3V/5V 0.1A 8MSOP
标准包装: 50
类型: 升压(升压)
输出类型: 固定
输出数: 1
输出电压: 3.3V,5V
输入电压: 1 V ~ 5 V
PWM 型: 电流模式,混合
频率 - 开关: 600kHz
电流 - 输出: 100mA
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 8-TSSOP,8-MSOP(0.118",3.00mm 宽)
包装: 管件
供应商设备封装: 8-MSOP
LT1307/LT1307B
APPLICATIO S I FOR ATIO
away from 455kHz. Figure 8 shows the noise spectrum of
the converter with the load increased to 20mA. The
LT1307 shifts out of Burst Mode operation, eliminating
low frequency ripple. Spectral energy is present only at
the switching fundamental and its harmonics. Noise
voltage measures – 5dBmV RMS or 560 μ V RMS at the
575kHz switching frequency, and is below – 60dBmV RMS
for all other frequencies in the range. By combining Burst
Mode with fixed frequency operation, the LT1307 keeps
noise away from 455kHz.
To eliminate the low frequency noise of Figure 6, the
LT1307 can be replaced with the LT1307B. Figure 9
details the spectral noise at the output of Figure 1’s circuit
using an LT1307B at 5mA load. Although spectral energy
is present at 333kHz due to alternate pulse skipping, all
Burst Mode operation spectral components are gone.
Alternate pulse skipping can be eliminated by increasing
inductance.
FREQUENCY COMPENSATION
0
–10
–20
–30
–40
–50
–60
–70
–80
RBW = 100Hz
Obtaining proper values for the frequency compensation
network is largely an empirical, iterative procedure, since
variations in input and output voltage, topology, capacitor
value and ESR, and inductance make a simple formula
elusive. As an example, consider the case of a 1.25V to
3.3V boost converter supplying 50mA. To determine
optimum compensation, the circuit is built and a transient
load is applied to the circuit. Figure 10 shows the setup.
–90
10 μ H
MBR0520L
–100
255
455
655
V OUT
FREQUENCY (kHz)
V IN
SW
1M
66 ?
1307 F08
SHDN
Figure 8. With Converter Delivering 20mA, Low Frequency
Sidebands Disappear. Noise is Present Only at the 575kHz
Switching Frequency
1 μ F
1.25V
R
V C
LT1307
GND
FB
3300 ?
10 μ F*
590k
0
C
50 ?
–10
–20
–30
*CERAMIC
Figure 10. Boost Converter with Simulated Load
1307 ? F10
–40
–50
–60
–70
–80
–90
Figure 11a details transient response without compensa-
tion components. Although the output ripple voltage at a
1mA load is low, allowing the error amplifier to operate
wideband results in excessive ripple at a 50mA load. Some
kind of loop stabilizing network is obviously required. A
–100
205
455
FREQUENCY (kHz)
705
LT1307 ? F09
100k/22nF series RC is connected to the V C pin, resulting
in the response pictured in Figure 11b. The output settles
in about 7ms to 8ms. This may be acceptable, but we can
Figure 9. LT1307B at 5mA Load Shows No Audio Components
or Sidebands About Switching Frequency, 333kHz
Fundamental Amplitude is –10dBmV, or 316 μ V RMS
do better. Reducing C to 2nF gives Figure 11c’s response.
This is clearly in the right direction. After another order of
magnitude reduction, Figure 11d’s response shows some
1307fa
10
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LT1307CMS8#TR 功能描述:IC REG BOOST 3.3V/5V 0.1A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压(升压) 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式,混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC(0.154",3.90mm 宽) 包装:带卷 (TR) 供应商设备封装:8-SOIC
LT1307CMS8#TRPBF 功能描述:IC REG BOOST 3.3V/5V 0.1A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压(升压) 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式,混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC(0.154",3.90mm 宽) 包装:带卷 (TR) 供应商设备封装:8-SOIC
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