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参数资料
| 型号： | LT3689IUD-5#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/34页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 0.7A 16QFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 3.6 V ~ 36 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 500kHz ~ 2MHz |
| 电流 - 输出： | 700mA |
| 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-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-QFN-EP（3x3） |
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LT3689/LT3689-5
APPLICATIONS INFORMATION
Another way to lower the start-up voltage is by using a
resistor divider on the EN/UVLO pin (see the Shutdown
and Undervoltage Lockout section). A resistor divider on
EN/UVLO pin programs the turn-on threshold to slightly
higher than the minimum V IN voltage required to run at full
load. Below the EN/UVLO high voltage, the part will stay
shut off and the output cap will remain discharged during
the worse case slow V IN ramp. When the EN/UVLO pin
crosses the EN/UVLO high threshold, the part will turn on
and the empty output capacitor will provide enough load
to bring the output voltage in regulation. This technique
significantly lowers the start-up voltage of the circuit. The
plot in Figure 7 depicts the minimum load required to start
and run (as a function of input voltage). It also depicts the
benefit of programming the EN/UVLO threshold to lower
the start-up voltage at low load currents. At light loads, the
inductor current becomes discontinuous and the effective
duty cycle can be very high. This reduces the minimum input
voltage to approximately 300mV above V OUT . At higher load
currents, the inductor current is continuous and the duty
cycle is limited by the maximum duty cycle of the LT3689,
requiring a higher input voltage to maintain regulation.
Soft-Start
The LT3689 has an internal soft-start that gradually ramps
up the switch current limit from about 100mA to the switch’s
maximum current limit in typical value of 150μs, as shown
in Figure 8. This feature limits the inrush current during
start-up and prevents the switch current from spiking when
the EN/UVLO pin crosses the UVLO threshold. A soft-start
sequence is also initiated right after a V IN overvoltage/
undervoltage lockout, or thermal shutdown fault in order
to prevent the switch current from suddenly jumping to
its maximum current limit.
8.0
7.5
7.0
6.5
6.0
5.5
TO START:
EN/UVLO TIED TO V IN
TO START: EN/UVLO HIGH
THRESHOLD = 6.15V
6.0
5.5
5.0
4.5
4.0
3.5
TO START:
EN/UVLO TIED TO V IN
TO START: EN/UVLO HIGH
THRESHOLD = 4.85V
5.0
1
TO RUN
10
100
1000
3.0
1
TO RUN
10
100
1000
V OUT = 5V
L = 8.2μH
LOAD (mA)
f SW = 800KHz
T A = 25°C
3589 F07a
LOAD (mA)
V OUT = 3.3V f SW = 800KHz
L = 8.2μH T A = 25°C
3589 F07b
Figure 7. LT3689 Minimum V IN to Start and Run vs Load
V OUT
2V/DIV
I L
0.5A/DIV
I VIN
0.2A/DIV
20μs/DIV
V IN = 12V
V OUT = 5V
3689 F08
f = 2MHz
C IN = 1μF CERAMIC + 100μF ELECTROLYTIC
Figure 8. Internal Soft-Start
For more information www.linear.com/LT3689
3689fe
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3689IUD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| LT3689IUD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Step-Down Regulator with Power-On Reset and Watchdog Timer |
| LT3690 | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator |
| LT3690EUFE#PBF | 功能描述:IC REG BUCK SYNC ADJ 4A 26QFN 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 |
| LT3690EUFE#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 4A 26QFN 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 |
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