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参数资料
| 型号： | LT1939EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/24页 |
| 文件大小： | 349K |
| 描述： | IC REG DL BUCK/LINEAR 12DFN |
| 标准包装： | 121 |
| 拓扑： | 降压（降压）（1），线性（LDO）（1） |
| 功能： | 任何功能 |
| 输出数： | 2 |
| 频率 - 开关： | 500kHz ~ 2.4MHz |
| 电压/电流 - 输出 1： | 0.8 V ~ 24.25 V，2A |
| 电压/电流 - 输出 2： | 0.8 V ~ 24.25 V，1A |
| 带 LED 驱动器： | 无 |
| 带监控器： | 无 |
| 带序列发生器： | 无 |
| 电源电压： | 3 V ~ 25 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 12-WFDFN 裸露焊盘 |
| 供应商设备封装： | 12-DFN |
| 包装： | 管件 |
LT1939
17
1939f
is much lower than the switching frequency. A phase lead
capacitor (C
PL
) across the feedback divider may improve
the transient response.
Synchronization
The R
T
/SYNC pin can be used to synchronize the LT1939
to an external clock source. Driving the R
T
/SYNC resistor
with a clock source triggers the synchronization detection
circuitry. Once synchronization is detected, the rising edge
of SW will be synchronized to the rising edge of the R
T
/SYNC
pin signal. An AGC loop will adjust slope compensation
to avoid subharmonic oscillation.
The synchronizing clock signal input to the LT1939 must
have a frequency between 250kHz and 2.5MHz, a duty
cycle between 20% and 80%, a low state below 0.5V and
a high state above 1.6V. Synchronization signals outside
of these parameters will cause erratic switching behavior.
The R
T
/SYNC resistor should be set such that the free
running frequency ((V
RT/SYNC
V
SYNCLO
)/R
RT/SYNC
) is
approximately equal to the synchronization frequency. If
the synchronization signal is halted, the synchronization
detection circuitry will timeout in typically 10約 at which
time the LT1939 reverts to the free-running frequency
based on the current through R
T
/SYNC. If the R
T
/SYNC
resistor is held above 1.6V at any time, switching will be
disabled.
If the synchronization signal is not present during regu-
lator start-up (for example, the synchronization circuitry
is powered from the regulator output) the R
T
/SYNC pin
must see an equivalent resistance to ground between 15k
and 200k until the synchronization circuitry is active for
proper start-up operation.
If the synchronization signal powers up in an undetermined
state (V
OL
, V
OH
, Hi-Z), connect the synchronization clock
to the LT1939 as shown in Figure 7. The circuit as shown
will isolate the synchronization signal when the output
voltage is below 90% of the regulated output. The LT1939
will start-up with a switching frequency determined by the
resistor from the R
T
/SYNC pin to ground.
APPLICATIONS INFORMATION
Figure 6. Model for Loop Response
Figure 7. Synchronous Signal Powered from Regulators Output
If the synchronization signal powers up in a low impedance
state (V
OL
), connect a resistor between the R
T
/SYNC pin
and the synchronizing clock. The equivalent resistance
seen from the R
T
/SYNC pin to ground will set the start-up
frequency.
If the synchronization signal powers up in a high impedance
state (Hi-Z), connect a resistor from the R
T
/SYNC pin to
ground. The equivalent resistance seen from the R
T
/SYNC
pin to ground will set the start-up frequency.
If the synchronization signal changes between high and
low impedance states during power up (V
OL
, Hi-Z), connect
SW
LT1939
FB
V
C
0.8V
C
F
C
PL
V
OUT1
C1
C1
1939 F06
C
C
R
C
R1
ESR
TANTALUM
OR
POLYMER
CERAMIC
R2
4M
ERROR AMP
g
m
= 250糾hos
CURRENT MODE
POWER STAGE
g
m
= 3mho
12
8
5
LT1939
SYNCHRONIZATION
CIRCUITRY
LDRV
PG
R
T
/SYNC
1939 F07
V
CC
CLK
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1939EDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| LT1939IDD#PBF | 功能描述:IC REG DL BUCK/LINEAR 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT1939IDD#TRPBF | 功能描述:IC REG DL BUCK/LINEAR 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LT1939IDD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| LT1939IDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
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