Kingbor Technology Co.,Ltd
TEL:(86)0755-26508846 FAX:(86)0755-26509052
KB4312
Very Low
Cost
Tiny Package, High Performance, Constant Current
Switching Regulator for White LED
FEATURES
•Operating Voltage:2.5V~6.5V
•High Operating Frequency: 1.2MHz
•High Efficiency: Up to 92%
•High Output Voltage: Up to 28V(max)
•Shutdown Current <1 A
•18V Output Over-voltage protection (ADJ)
•Digital Dimming Control.
•Built-in Cycle-by Cycle Current-limiting.
•Built-in Soft-Start Function.
•0.24V Low Reference Voltage(+/-5%)
•Tiny SOT23 Package
DESCRIPTION
The KB4312 step-up converter drives white LEDs
with a constant current to provide backlight in cell
phones, PDAs, and other hand-held devices. It
features allowing series connection of the white
LEDs so that the LED currents are identical for
uniform brightness. An enable input can be pulsed
repeatedly to adjust LED’s brightness. The fast 1.2
MHz current-mode PWM control allows for smaller
capacitor and inductor. Fault condition protection
uses cycle-by-cycle current limiting to sense
maximum inductor current, thermal protection and
over-voltage protection. Also included soft-start
eliminates inrush current during start-up. The 0.24V
low reference voltage minimized the power loss
across the current-setting resistor.
The KB4312 is available in SOT23 packages
APPLICATIONS
• LED Module
• LED Backlight for LCD Display (1
”
~6.5
”
)
• Constant Current Source
SIMPLIFIED BLOC DIAGRAM
VIN
6
1
Soft-Start
LX
EN
4
ON/OFF
Control
Logic / PWM
Dimming
Control
CTL
+
VREF
0.240V
VBG
1.27V
N
Control Logic
FB
OVP
3
5
17V
-
KB4312B FB=240mV
KB4312A FB=1.27V
VBG
+
-
Overvoltage
Protection
Current Limit
0.25A
+
-
CTL
2
GND
REV: 3.2
1
KINGBOR [ KINGBOR TECHNOLOGY CO ]
