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| 型号： | LT3689EUD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/34页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.7A 16QFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 34.2 V |
| 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
V H V L
R3 = 4k
R4 =
V H 1.26V
Synchronization
To select low ripple Burst Mode operation, tie the SYNC pin
below 0.3V (this can be ground or a logic output). Synchro-
nizing the LT3689 oscillator to an external frequency can
be done by connecting a square wave (with positive and
negative pulse width >80ns) to the SYNC pin. The square
wave amplitude should have valleys that are below 0.3V
and peaks that are above 1V (up to 6V).
The LT3689 will not enter Burst Mode operation at low
output loads while synchronized to an external clock, but
instead will skip pulses to maintain regulation.
The LT3689 may be synchronized over a 350kHz to 2.5MHz
range. The R T resistor should be chosen to set the LT3689
switching frequency 20% below the lowest synchronization
input. For example, if the synchronization signal will be
350kHz and higher, the R T should be chosen for 280kHz.
To assure reliable and safe operation, the LT3689 will only
synchronize when the output voltage is above 90% of its
regulated voltage. It is therefore necessary to choose a
large enough inductor value to supply the required output
current at the frequency set by the R T resistor (see the
Inductor Selection section). It is also important to note
that the slope compensation is set by the R T value. When
the sync frequency is much higher than the one set by
R T , the slope compensation will be significantly reduced,
which may require a larger inductor value to prevent
subharmonic oscillation. The minimum inductor value
should be calculated using the RT programmed frequency
to avoid subharmonic oscillation.
Shutdown and Undervoltage Lockout
Figure 9 shows how to add undervoltage lockout (UVLO)
to the LT3689. Typically, UVLO is used in situations where
the input supply is current limited, or has a relatively high
source resistance. A switching regulator draws constant
power from the source, so source current increases as
source voltage drops. This looks like a negative resistance
load to the source and can cause the source to current limit
or latch low under low source voltage conditions. UVLO
prevents the regulator from operating at source voltages
where the problems might occur. An internal comparator
will force the part into shutdown below the minimum V IN
of 3.4V. This feature can be used to prevent excessive
discharge of battery-operated systems. If an adjustable
UVLO threshold is required, the EN/UVLO pin can be used.
The threshold voltage of the EN/UVLO pin comparator is
1.26V. Current hysteresis is added above the EN threshold.
This can be used to set voltage hysteresis of the UVLO
using the following:
4μA
1.26V
4μA
R3
V IN
LT3689
1.25V
V C
R3
EN/UVLO
22
C1
R4
4μA
Figure 9. Undervoltage Lockout
For more information www.linear.com/LT3689
SS
3689 F09
3689fe
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| LT3689HMSE#PBF | 功能描述:IC REG BUCK ADJ 0.7A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
| LT3689HMSE#TRPBF | 功能描述:IC REG BUCK ADJ 0.7A 16MSOP 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 |
| LT3689HMSE-5#PBF | 功能描述:IC REG BUCK 5V 0.7A 16MSOP 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 |
| LT3689HMSE-5#TRPBF | 功能描述:IC REG BUCK 5V 0.7A 16MSOP 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 |
| LT3689HMSE-5-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 |
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