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| 型号： | LT3689EMSE-5#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.95 A SWITCHING REGULATOR, 2160 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 15/32页 |
| 文件大小： | 2188K |
| 代理商： | LT3689EMSE-5#PBF |
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LT3689/LT3689-5
22
3689fd
Synchronization
To select low ripple Burst Mode operation, tie the SYNC pin
below0.3V(thiscanbegroundoralogicoutput).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.
TheLT3689maybesynchronizedovera350kHzto2.5MHz
range. The RT resistor should be chosen to set the LT3689
switchingfrequency20%belowthelowestsynchronization
input. For example, if the synchronization signal will be
350kHz and higher, the RT 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 RT resistor (see the
Inductor Selection section). It is also important to note
that the slope compensation is set by the RT value. When
the sync frequency is much higher than the one set by
RT, 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 VIN
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:
R3 =
VH VL
4A
4k
R4 =
1.26V
VH 1.26V
R3
4A
APPLICATIONS INFORMATION
Figure 9. Undervoltage Lockout
1.25V
4A
R3
R4
C1
EN/UVLO
LT3689
VIN
SS
VC
3689 F09
–
+
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3689EMSE-5-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 |
| LT3689EMSE-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 |
| LT3689EMSE-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 |
| LT3689EUD#PBF | 功能描述:IC REG BUCK ADJ 0.7A 16QFN 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 |
| LT3689EUD#TRPBF | 功能描述:IC REG BUCK ADJ 0.7A 16QFN 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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