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| 型号： | LT1976EFE |
| 厂商： | Linear Technology |
| 文件页数： | 26/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.5A 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.2 V ~ 54 V |
| 输入电压： | 3.3 V ~ 60 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
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LT1976/LT1976B
APPLICATIO S I FOR ATIO
The LT1976 uses current mode control. This alleviates
many of the phase shift problems associated with the
inductor. The basic regulator loop is shown in Figure 12.
The LT1976 can be considered as two g m blocks, the error
amplifier and the power stage.
Figure 13 shows the overall loop response with a 330pF V C
capacitor and a typical 100 μ F tantalum output capacitor.
The response is set by the following terms:
Error amplifier: DC gain is set by g m and R O :
EA Gain = 650 μ ? 1.5M = 975
The pole set by C F and R L :
EA Pole = 1/(2 π ? 1.5M ? 330pF) = 322Hz
Unity gain frequency is set by C F and g m :
EA Unity Gain Frequency = 650 μ F/(2 π ? 330pF)
= 313kHz
Powerstage: DC gain is set by g m and R L (assume 10 Ω ):
PS DC Gain = 3 ? 10 = 30
Pole set by C OUT and R L :
PS Pole = 1/(2 π ? 100 μ F ? 10) = 159Hz
Unity gain set by C OUT and g m :
PS Unity Gain Freq = 3/(2 π ? 100 μ F) = 4.7kHz.
Tantalum output capacitor zero is set by C OUT and C OUT
ESR
Output Capacitor Zero = 1/(2 π ? 100 μ F ? 0.1) = 15.9kHz
The zero produced by the ESR of the tantalum output
capacitor is very useful in maintaining stability. If better
transient response is required, a zero can be added to the
loop using a resistor (R C ) in series with the compensation
capacitor. As the value of R C is increased, transient
response will generally improve but two effects limit its
value. First, the combination of output capacitor ESR and
a large R C may stop loop gain rolling off altogether.
Second, if the loop gain is not rolled off sufficiently at the
switching frequency output ripple will perturb the V C pin
enough to cause unstable duty cycle switching similar to
subharmonic oscillation. This may not be apparent at the
output. Small-signal analysis will not show this since a
continuous time system is assumed. If needed, an addi-
tional capacitor (C F ) can be added to form a pole at
typically one-fifth the switching frequency (if R C = 10k,
C E = 1500pF, C F = 330pF)
When checking loop stability the circuit should be oper-
ated over the application’s full voltage, current and tem-
perature range. Any transient loads should be applied and
the output voltage monitored for a well-damped behavior.
11
LT1976
CURRENT MODE
POWER STAGE
g m = 3
g m = 650 μ
V C ERROR
AMP
–
SW
FB
2
R1
12
R2
C FB
OUTPUT
ESR
100
50
V OUT = 3.3V
C OUT = 100 μ F, 0.1 Ω
C F = 330pF
R L /C L = NC
I LOAD = 330mA
100
135
90
R C
1.6M
+
C F
C C
1.26V
1976 F13
C OUT
0
–50
45
0
Figure 13. Model for Loop Response
10
100
1k 10k
FREQUENCY (Hz)
100k
1M
1976 F14
Figure 14. Overall Loop Response
1976bfg
26
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相关代理商/技术参数 |
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|---|---|
| LT1976EFE#PBF | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1976EFE#TR | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1976EFE#TRPBF | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1976EFEPBF | 制造商:Linear Technology 功能描述:LT1976 adj PWM 1.5A SD dc-dc converter 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 60V TSSOP16EP |
| LT1976HFE | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage 1.5A, 200kHz Step-Down Switching Regulator with 100μA Quiescent Current |
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