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參數(shù)資料
| 型號： | LT1937ES5#TRM |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.32 A SWITCHING REGULATOR, 1600 kHz SWITCHING FREQ-MAX, PDSO5 |
| 封裝： | PLASTIC, TSOT-23, 5 PIN |
| 文件頁數(shù)： | 7/12頁 |
| 文件大?。?/td> | 358K |
| 代理商： | LT1937ES5#TRM |
4
LT1937
1937f
–
+
–
+
RQ
S
0.2
SW
DRIVER
COMPARATOR
2
SHDN
4
1
VIN
3
FB
95mV
5
–
+
Σ
RAMP
GENERATOR
RC
CC
1.2MHz
OSCILLATOR
GND
1937 BD1
Q1
A2
A1
SHUTDOWN
VREF
1.25V
(PIN 6 FOR
SC70 PACKAGE)
(PINS 2 AND 5 FOR
SC70 PACKAGE)
BLOCK DIAGRA
W
OPERATIO
U
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
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.
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
external components as specified for 15mA operation. As
current is further reduced, the device will begin skipping
Figure 2. LT1937 Block Diagram
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.
VSW
5V/DIV
IL2
50mA/DIV
VOUT
100mV/DIV
0.2
s/DIV
1937 F03
Figure 3. Switching Waveforms at ILED = 4mA, VIN = 3.6V
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1937ESC6 | 制造商:LINER 制造商全稱: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 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標準包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓撲:開路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT1937ESC6#TRM | 功能描述:IC LED DRVR WHITE BCKLGT SC-70-6 RoHS:否 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標準包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓撲:開路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT1937ESC6#TRMPBF | 功能描述:IC LED DRVR WHITE BCKLGT SC-70-6 RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標準包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓撲:開路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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