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| 型号： | LT1937ES5#TRM |
| 厂商： | Linear Technology |
| 文件页数： | 4/12页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVR WHITE BCKLGT TSOT-5 |
| 标准包装： | 1 |
| 恒定电流： | 是 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 800kHz ~ 1.6MHz |
| 电源电压： | 2.5 V ~ 10 V |
| 输出电压： | 36V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOT-23-5 细型，TSOT-23-5 |
| 供应商设备封装： | TSOT-23-5 |
| 包装： | 剪切带 (CT) |
| 工作温度： | -40°C ~ 85°C |
| 其它名称： | LT1937ES5 LT1937ES5#TRMCT LT1937ES5-ND |
LT1937
BLOCK DIAGRA
V IN
(PIN 6 FOR
SC70 PACKAGE) 5
FB
3
–
COMPARATOR
1 SW
V REF
1.25V
95mV
+
A1
R C
A2
R
S
Q
DRIVER
Q1
C C
Σ
+
0.2 ?
–
RAMP
SHDN
GENERATOR
4
SHUTDOWN
1.2MHz
(PINS 2 AND 5 FOR
SC70 PACKAGE)
2 GND
1937 BD1
OSCILLATOR
Figure 2. LT1937 Block Diagram
OPERATIO
The LT1937 uses a constant frequency, current mode
control scheme to provide excellent line and load regula-
tion. Operation can be best understood by referring to the
block diagram in Figure 2. At the start of each oscillator
cycle, the SR latch is set, which turns on the power switch
Q1. A voltage proportional to the switch current is added
to a stabilizing ramp and the resulting sum is fed into the
positive terminal of the PWM comparator A2. When this
voltage exceeds the level at the negative input of A2, the SR
latch is reset turning off the power switch. The level at the
negative input of A2 is set by the error amplifier A1, and is
simply an amplified version of the difference between the
feedback voltage and the reference voltage of 95mV. In
this manner, the error amplifier sets the correct peak
pulses. This will result in some low frequency ripple,
although the LED current remains regulated on an average
basis down to zero. The photo in Figure 3 details circuit
operation driving three white LEDs at a 4mA load. Peak
inductor current is less than 50mA and the regulator
operates in discontinuous mode, meaning the inductor
current reaches zero during the discharge phase. After the
inductor current reaches zero, the switch pin exhibits
ringing due to the LC tank circuit formed by the inductor
in combination with switch and diode capacitance. This
ringing is not harmful; far less spectral energy is contained
in the ringing than in the switch transitions. The ringing
can be damped by application of a 300 ? resistor across
the inductor, although this will degrade efficiency.
current level to keep the output in regulation. If the error
amplifier’s output increases, more current is delivered to
the output; if it decreases, less current is delivered.
V SW
Minimum Output Current
The LT1937 can regulate three series LEDs connected at
low output currents, down to approximately 4mA from a
4.2V supply, without pulse skipping, using the same
5V/DIV
I L2
50mA/DIV
V OUT
100mV/DIV
external components as specified for 15mA operation. As
0.2 μ s/DIV
1937 F03
current is further reduced, the device will begin skipping
Figure 3. Switching Waveforms at I LED = 4mA, V IN = 3.6V
1937f
4
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1937ESC6 | 制造商:LINER 制造商全称:Linear Technology 功能描述:White LED Step-Up Converter in SC70 and ThinSOT |
| LT1937ESC6#PBF | 制造商:Linear Technology 功能描述:LED DRVR 6Segment 3.3V/5V/9V 6-Pin SC-70 制造商:Linear Technology 功能描述:SP-SWREG/LED Driver, CUT TAPE White LED Step-up Converter |
| LT1937ESC6#TR | 功能描述:IC LED DRVR WHITE BCKLGT SC-70-6 RoHS:否 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT1937ESC6#TRM | 功能描述:IC LED DRVR WHITE BCKLGT SC-70-6 RoHS:否 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT1937ESC6#TRMPBF | 功能描述:IC LED DRVR WHITE BCKLGT SC-70-6 RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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