LT3477EUF#TRPBF Linear Technology, LT3477EUF#TRPBF Datasheet - Page 12

• Manufacturer Part Number: LT3477EUF#TRPBF
• Description: IC LED DRVR HP CONST CURR 20-QFN
• Manufacturer: Linear Technology
• Type: High Power, Constant Currentr

Specifications of LT3477EUF#TRPBF

• Constant Current: Yes
• Constant Voltage: Yes
• Topology: Flyback, PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: General Purpose
• Type - Secondary: White LED
• Frequency: 200kHz ~ 3.5MHz
• Voltage - Supply: 2.5 V ~ 25 V
• Mounting Type: Surface Mount
• Package / Case: 20-QFN
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 3A
• Internal Switch(s): Yes
• Efficiency: 93%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -

APPLICATIONS INFORMATION
LT3477
12
200mA/DIV
5V/DIV
1A/DIV
PWM
I
LED
I
L
Figure 7b. PWM Dimming Waveforms
V
4 LEDs
300mA
IN
= 5V
5V
0
C1: TAIYO YUDEN EMK316BJ335ML
C2: TAIYO YUDEN UDK325BJ106MM
L1: TOKO D53LC (PN# A915AY-2ROM)
D1: ZETEX ZLLS1000
D2: DIODES INC 1N4148
NMOS1: ZETEX 2N7002
NMOS2: FAIRCHILD FDG327N
LED1 TO LED4: LUMILEDS LXHL-BW02
PWM FREQ = 100Hz
BOOST
100Hz
PWM
10μs/DIV
100k
Figure 7a. 5V to 4 White LEDs: Boost With PWM Dimming
V
5V
IN
D2
3477 F07b
C1
3.3μF
C
33nF
SS
NMOS1
R
2.4k
C
C
10nF
C
SS
I
V
I
I
SHDN
V
SP1
ADJ1
ADJ2
IN
C
I
SN1
LT3477
GND
2.0μH
L1
SW
V
I
I
FBN
FBP
SP2
SN2
REF
R
85
80
75
70
65
55
50
3477 F07a
60
T
D1
0
Figure 7c. Effi ciency and LED Current
vs PWM Duty Cycle
6.81k
20
1M
75k
PWM DUTY CYCLE (%)
EFFICIENCY
LED CURRENT
40
V
BOOST
4 LEDs, 300mA
PWM FREQUENCY = 100Hz
OUT
NMOS2
R
0.33Ω
IN
SENSE
= 5V
LED1
LED2
LED3
LED4
C2
10μF
60
300mA
80
3477 F07c
100
350
200
150
300
250
100
50
0
3477fc