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GM1937 데이터시트 PDF




Gamma에서 제조한 전자 부품 GM1937은 전자 산업 및 응용 분야에서
광범위하게 사용되는 반도체 소자입니다.


PDF 형식의 GM1937 자료 제공

부품번호 GM1937 기능
기능 WHITE LED STEP-UP CONVERTER
제조업체 Gamma
로고 Gamma 로고


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GM1937 데이터시트, 핀배열, 회로
GM1937
WHITE LED STEP-UP CONVERTER
Description
Features
The GM1937 is a step-up DC/DC converter specifically ‹ High Efficiency: 84% Typical
designed to drive white LEDs with a constant current. ‹ 36V internal Switch
The device can drive two, three or four LEDs in series
from a Li-Ion cell. Series connection of the LEDs
provides identical LED currents resulting in uniform
brightness and eliminating the need for ballast
‹ Fast 1.2MHz Switching Frequency
‹ Drives Up to three LEDs from a 2.8V
Supply
‹ Drives Up to six LEDs from a 5V
resistors.
Supply
The output capacitor can be as small as 0.22µF,
saving space versus alternative solutions. A low 95mV
feedback voltage minimizes power loss for better
‹ External Matched LED Current
‹ Uses Tiny 1mm height inductor
‹ Requires Only 0.22 F Output
Capacitor
‹ Low profile TSOT package
Application
Cellular Phones
PDA, Handheld Computers
Digital Cameras
MPS3 Players
GPS Receivers
Typical Application Circuits
VIN
3V to 5V
OFF ON
22µH
1µF VIN
SW
GM1937
CE FB
GND
0.22µF
R1
6.34
Figure 1
Li-Ion Powered Driver for Three White LEDs
90
85
80 VIN = 3.0V
75
VIN = 3.6V
70
65
60 0 5 10 15 20
LED CURRENT (mA)
1
Free Datasheet http://www.datasheet4u.com/




GM1937 pdf, 반도체, 판매, 대치품
GM1937
WHITE LED STEP-UP CONVERTER
Electrical Characteristics (TA = 25 , Vcc = 3V, VCE = 3V, unless otherwise noted)
Parameter
Symbol
Condition
Min Typ Max Unit
Feeback Voltage
FB Pin Bias Current
VFB ISW = 100mA, Duty Cycle = 66% 86
IFB 10
95 104 mV
45 100 nA
Supply Current
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch VCESAT
Switch Leakage current
CE Voltage High
ICC(ON)
ICC(OFF)
fSW
DMAX
ISW
VSAT
ILEAK
VCE = 0V
ISW = 250mA
VSW = 5V
1.9 2.5 mA
0.1 1.0 µA
0.8 1.2 1.6 MHz
85 90
%
320 mA
350
0.00
1
1.5
5
mV
µA
V
CE Voltage Low
0.4 V
CE Pin Bias Current
ICE
65 µA
4

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GM1937 전자부품, 판매, 대치품
GM1937
WHITE LED STEP-UP CONVERTER
Application Information – Cont’d
Dimming Control
There are four different types of dimming control:
1. Using a PWM Signal to SHDN Pin
With the PWM signal applied to the CE pin, the GM1937 is turned on or off by the PWM signal. The
LEDs operate at either zero or full current. The average LED current increases proportionally with
the duty cycle of the PWM signal. A 0% duty cycle will turn off the GM1937 and corresponds to zero
LED current. A 100% duty cycle corresponds to full current. The typical frequency range of the PWM
signal is 1kHz to 10kHz. The magnitude of the PWM signal should be higher than the minimum CE
voltage high.
2. Using a DC Voltage
For some applications, the preferred method of brightness control is a variable DC voltage to adjust
the LED current. The dimming control using a DC voltage is shown in Figure 4. As the DC voltage
increases, the voltage drop on R2 increases and the voltage drop on R1 decreases. Thus, the LED
current decreases. The selection of R2 and R3 will make the current from the variable DC source
much smaller than the LED current and much larger than the FB pin bias current. For VDC range
from 0V to 2V, the selection of resistors in Figure 4 gives dimming control of LED current from 0mA
to 15mA.
GM1937
FB
R3 R2
90K
VDC
5K
GM1937
PWM
10K
FB
R3
90K
R2
5K
R1
6.34
0.1µF
R1
6.34
Figure 4. Dimming Control Using a DC Voltage
Figure 5. Dimming Control Using a Filtered
PWM Signal
3. Using a Filtered PWM Signal
The filtered PWM signal can be considered as an adjustable DC voltage. It can be used to replace
the variable DC voltage source in dimming control. The circuit is shown in Figure 5.
4. Using a Logic Signal
For applications that need to adjust the LED current is discrete steps, a logic signal can be used as
shown in Figure 6. R1 sets the minimum LED current (when the NMOS is OFF). RINC sets how
much the LED current increases when the NMOS is turned on. The selection of R1 and RINC can
be found in table 3
GM1937
FB
RINC
Logic Signal
R1
Figure 5. Dimming Control Using a Logic Signal
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