A8430EEK Allegro Microsystems Inc, A8430EEK Datasheet - Page 9

• Manufacturer Part Number: A8430EEK
• Description: IC LED DRVR WHITE BCKLGHT 5-MLPD
• Manufacturer: Allegro Microsystems Inc
• Type: Backlight, White LEDr

Specifications of A8430EEK

• Constant Current: Yes
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 1.2MHz
• Voltage - Supply: 2.5 V ~ 10 V
• Voltage - Output: 36V
• Mounting Type: Surface Mount
• Package / Case: 5-WDFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 20mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Efficiency: -

Overvoltage protection for the A8430 requires a Zener diode
to clamp the output voltage, as shown in schematic 5. The
Zener voltage should be greater than the maximum output
voltage of the LED string. The Zener diode also should be
able to sink more than 0.1 mA of current.
Parallel LED Strings
The A8430 can be used to power parallel strings of LEDs,
which have the same number of LEDs on each string. It is
important that the voltage drop is the same across all of the
parallel strings, to ensure that all of the LEDs are illuminated
and that the current though each string is equal.
A typical circuit with two parallel strings is shown in
schematic 6. The coversion efficiency of this configuration is
shown in chart 2.
White LED Driver Constant Current Step-up Converter
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
Schematic 5. Overvoltage protection with Zener clamp
Schematic 6. Parallel strings of LEDs
Chart 2. Conversion efficiency when driving two parallel strings
of varying lengths
Li-ion
2.5V to
4.2V
Conversion Efficiency for Two Parallel Strings
Li-ion
2.5V to
4.2V
95
90
85
80
75
70
65
2
C1
1µF
C1
1µF
3
VIN
Enable
VIN
Enable
EN
EN
4
A8430
GND
A8430
GND
L1
22µH
Input Voltage (V)
L1
22µH
5
FB
FB
SW
SW
6
Two 3-LED strings
Two 4-LED strings
Two 7-LED strings
D1
D1
R1
6.3Ω
7
R2
1kΩ
8
9
R2
6.3Ω
A8430
R1
6.3Ω
10
C2
0.22µF
C2
0.22µF
8