LTC3454 Просмотр технического описания (PDF) - Linear Technology
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LTC3454 Datasheet PDF : 12 Pages
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LTC3454
TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency vs Temperature
1100
VOUT = 3V
1080
1060
1040
1020
VIN = 4.2V
VIN = 5.5V
1000
980
960
VIN = 3.6V
VIN = 2.7V
940
920
900
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
3454 G16
Output Voltage Ripple
Back Page Application
LED Power Efficiency vs LED Current
100
95
90
85
80
75
70 VIN = 3.6V
TA = 25°C
65 EFFICIENCY = (VOUT – VLED)ILED/VINIIN
FRONT PAGE APPLICATION
60
100 200 300 400 500 600 700 800 900 1000
ILED (mA)
3454 G17
Start-Up Transient
Back Page Application
20mV/DIV
VIN = 3.6V
ILED = 500mA
500ns/DIV
3454 G19
0V, 0A
0V
VIN = 3.6V
ILED = 500mA
5ms/DIV
CH1, VOUT
1V/DIV
CH2, ILED
500mA
FINAL VALUE
CH3, VEN1
1V/DIV
3454 G19
PIN FUNCTIONS
EN1 (Pin 1): Enable Input Pin for ISET1 Current.
EN2 (Pin 2): Enable Input Pin for ISET2 Current.
ISET1 (Pin 3): LED Current Programming Pin. A resistor
to ground programs the current through the LED to ILED
= 3850(0.8V/RISET1). This amount of current adds to any
amount set by EN2/ISET2 if used.
ISET2 (Pin 4): LED Current Programming Pin. A resistor
to ground programs the current through the LED to ILED
= 3850(0.8V/RISET2). This amount of current adds to any
amount set by EN1/ISET1 if used.
LED (Pin 5): Low Dropout Output for LED Current Biasing.
Connect the LED between VOUT and the LED pin.
SW2 (Pin 6): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7μH/5μH.
VOUT (Pin 7): Buck-Boost Output Rail. Bypass to GND with
a ceramic capacitor. Recommended value is 10μF.
VC (Pin 8): Compensation Point for the Internal Error
Amplifier Output. Connect a ceramic capacitor from VC
to GND. Recommended value is 0.1μF.
VIN (Pin 9): Voltage Input Supply Pin (2.7V ≤ VIN ≤ 5.5V).
Bypass to GND with a ceramic capacitor. Recommended
value is 10μF.
SW1 (Pin 10): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7μH/5μH.
Exposed Pad (Pin 11): Ground Pin. Solder to PCB ground
for electrical contact and optimal thermal performance.
3454fa
5
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