KB4312 KINGBOR | Alldatasheet

Document overview

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  • PDF pages: 9

Technical content

  • Operating V oltage:2.5V~6.5V
  • High Operating Frequency: 1.2MHz
  • High Output V oltage: Up to 28V(max)
  • Shutdown Current <1PA
  • 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 V oltage(+/-5%)
  • Tiny SOT23 Package
  • LED Module
  • LED Backlight for LCD Display (1 ~6.5 )
  • Constant Current Source! 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 / LX -FB ON/OFF Control Logic / PWM Dimming Control GND Control Logic EN VREF 0.240V N VBG 1.27V VIN VBG OVP Overvoltage Protection Current Limit 0.25A CTL CTL 17V Soft-Start KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052
  • High Efficiency: Up to 92%

APPLICATIONS

” ” REV: 3.2 Very Low Cost KB4312B FB=240mV KB4312A FB=1.27V Tiny Package, High Performance, Constant Current Switching Regulator for White LED

Part number Package Marking GRE SOT23-5, Green Pin N0. Symbol I / O Description 1 LX I Step-up Regulator N-MOS Drain. Place output diode and inductor.

2 GND P Ground

3 FB I Step-Up Regulator Feedback Input. Connect a sense resistor from FB to ground. (KB4312B FB=240mV,KB4312A FB=1.27V)

4 EN I

Enable and Dimming Control Input. LED brightness and IC shutdown are controlled by the voltage on EN. Driving low for longer than 4ms to shutdown the IC.

5 OVP I Over-voltage protection input(ADJ)

6 VIN P Power supply. Parameter Rated Value Unit VIN voltage -0.3 to +6.5 V LX , OVP voltage -0.3 to +28 V EN , FB to GND -0.3 to +6.5 V Switch Current (I LX ) 0.25 A Continuous power dissipation (SOT23-6 Ta=+25 O C) 0.35 W Operating Junction Temperature Range -35 to 85 к Lead Temperature (Soldering 5 sec) 260 к Storage Temperature -65 to 125 к Package Thermal Resistance (Ә JA ) 250 к/W ESD Susceptibility (HBM) 2 KV ESD Susceptibility (MM) 200 V Note1:Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Exposure to absolute maximum rating conditions for extended periods may affect device reliability KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 PIN CONFIGURATION ORDER INFORMATION PIN DESCRIPTION (Note 1) ABSOLUTE MAXIMUM RATINGS KB4312A- LX GND V IN EN FB OVP SOT23-6 SOT23-6 LX GND V IN EN FB SOT23-5 SOT23-5 KB4312B KB4312A FB=240mV FB=1.27V Part number Package Marking GRE SOT23-6, Green 5121m,Date Code with one bottom line KB4312B- ATxxxx, xxxx: Date Code 5121x, x: Date Code

Min. Typ. Max. Unit Power supply voltage V IN 2.5 ѧ 6.5 V Operating temperature Top -30 +25 +85 к IN =2.5V , Ta=+25к, unless otherwise noted) Parameter Symbol Test Condition Min. Typ. Max. Units Operating V IN Range V IN V IN input V oltage 2.5 - 6.5 V Under V oltage Thershold UVLO V IN falling, 100mV hysteresis 1.4 1.5 1.6 V No Load Current I IN1 No Switching , FB>0.2V - 1 3 mA Shutdown Current I IN3 EN=0V - - 1 uA Feedback Reference (+/-5%) V FB 0.225 0.240 0.255 V Over-voltage Threshold V OVP 16 17 20 V Over-voltage Hysteresis 2 V OVP Leakage Current I OVP EN=0V - - 1 uA Output V oltage Line Regulation 2.5V< V IN <6.0V - 0.1 - % Switching Frequency f OSC 0.5 0.8 1.0 MHz Maximum Duty D MAX - 90 - % Soft-Start charging time t SS 0.05 0.2 ms Switching Current Limit ILX V IN =3.0V ,duty cycle=80% , - 0.15 - A LX ON Resistance R LX V IN =2.5V , ILX =750mA - 0.40 - Ө LX Leakage Current I Leakage V LX =16V , EN=0V - - 1 uA EN Input Current I EN EN=5V - - 1 uA V IH 1.5 - - V EN Input Level V IL - - 0.4 V EN low Shutdown Delay 4 ms EN Low Cycle Time t CYCL Note(1) 0.05 4 ms EN High Cycle Time t CYCH Note(1) 0.05 4 ms Note(1): t CYCL and t CYCH are included rising time and falling time of PWM signal. KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052

ELECTRICAL CHARACTERISTICS

RECOMMENDED OPERATION CONDITIONS Recommended PCB Layout Feedback Reference (+/-2%) V FB 1.245 1.270 1.295 V KB4312B KB4312A KB4312B KB4312B

Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current SHDN Pin Bias Current Switchin g Frequenc y 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 q C q C 100 q C 400 350 300 250 200 150 100 SHDN = 10V SHDN = 3.6V SHDN = SHDN = 2.7V 1.4 1.2 1.0 0.8 0.6 0.4 0.2 25 0 25 50 75 100 25 0 25 50 75 100 V IN (V) TEMPERATURE q TEMPERATURE q Feedback Bias Current Efficienc y vs Temperature V IN 3.6V LEDs 350 Current Limit vs Dut y C y cle I LED 20mA I LED 15mA I LED 10mA 300 250 200 150 100 –50 25 0 25 50 75 100 –50 05 0 1 0 0 0 20 40 60 80 100 TEMPERATURE TEMPERATURE q DUTY CYCLE

Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 APPLICATION CIRCUIT Figure 1a.KB4312 For 2 to 6 LEDs Back Light Unit.(Step-Up) KB4312B Rset 12R~51R LX OVP FB GND EN VCC VOUT=6~24VVin=2.7~6V 1uF PWM or ON/OFF 10uH 1N5819 1uF 20MA 240mV KB4312A LX FB GND EN VCC VOUT +15V (15mA)Vin=2.7~6V 1uF ON/OFF 10uH 1N5819 10uF 1.27V BAT54s 1uF 1uF -10V 10uF 10V 2.2K R1= ( VOUT 1.27V -1 ) x R2 510K 47K KB4312A LX FB GND EN VCC VOUT +15V(15mA) Vin=5~20V 1uF ON/OFF 10uH 10uF 1.27V BAT54s 1uF 1uF -10V 10uF 10V 2.2K R1= ( VOUT 1.27V -1 ) x R2 510K 47K 5.1V 1uF 1uF

The KB4312 is a high efficiency and constant current DC-DC converter IC which is designed primarily for use in LED module applications. The output voltage of the step-up converter can be set from Vin to 28V with external sense resistor. The device suits to drive series-connected LEDs and provides even illumination by sourcing the same output current through each LED. KB4312 also consists of a logic shutdown , cycle-by-cycle current-limited , soft-start functions. Logic control input or PWM duty cycle control allows easy adjustment of LEDs brightness and on/off control. The average LED current is proportionable the duty-cycle of the PWM signal. Typical PWM frequency should be between 100Hz and 1kHz. The boost converter operates in current-mode PWM and a constant frequency of 1.2 MHz. Depending on duty cycle of each switching cycle can regulate output voltage. On the rising edge of the internal clock , the control and driver logic block sets internal flip-flop when the output voltage is too low, which turns on the N-MOS. The external inductor current ramps up linearly, storing energy in a magnetic filed. Once peak current of inductor over trans-conductance output level , the N-MOS turns off, the flip-flop resets, and external schottky diode turns on. This forces the current through the inductor to ramp back down, transferring the energy stored in the magnetic field to the output capacitor and LEDs. To reduce external component amount , the device will be built-in internal loop compensation. ʳ Digital logic of EN provides an electrical ON/OFF control of the power supply. Connecting this pin to ground or to any voltage less than 0.4V and sustain the level over 4ms will completely turn off the regulator. In this state, current drain from the input supply is less than 1uA, the internal reference, error amplifier, comparators, and biasing circuitry turn off . If holding time of low level is less than 3ms on this pin, then the device only shutdown driver logic block. ʳ Digital logic of EN also provides LEDs brightness control by applying a PWM signal on EN pin. With this way, the LEDs operate with either zero or full current . The average LED current is proportional to the duty-cycle of the PWM signal. Typical PWM frequency should be between 100Hz and 1kHz. Output current is given by: PWMSSENSE PWMON LED TR TmVI u u 105 ʳ Where: T ON-PWM : On time of PWM signal T S-PWM : A cycle time of PWM signal If dimming control is not required , EN works as a simple on/off control. Drive EN high to enable the device , or drive EN low for shutdown. ʳ KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 Function Description Enable Control Dimming Control

Soft-start allows a gradual increase of the internal current-limit level for the step-up converter during power-up to reduce input surge currents. As the internal current source charges the internal soft-start capacitor, the peak N-MOS current is limited by the voltage on the capacitor. In another story, when toggle or a logic-level transition on EN pin from low to high, soft-start function must work to enable constant current charging internal capacitor. When soft-start process has finished or appeared falling edge of PWM signal on EN pin , soft-start capacitor must be discharged to ground level. The KB4312 provides cycle-by-cycle over-current protection. Current limit is accomplished using a separate dedicated comparator. The cycle-by-cycle current limit abbreviates the on-time of the N-MOS in event that the current of flowing N-MOS is greater than the current limit value. The current-limit feature protection against a hard short or over-current fault at the output. If V OVP is above 17V or LEDs are disconnected from the circuit, the FB pin is similar to pull down to ground with a sense resistor. This will cause N-MOS to switch with a maximum duty cycle and come out output over-voltage. This may cause the LX pin voltage to exceed its maximum voltage rating to damage built-in N-MOS. In the state, the OVLO protection circuitry stops the internal N-MOS . The KB4312 maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature difference between the die junction and ambient air, and the rate of any airflow. The power dissipation in the device depends on the operating conditions of the regulator. The step-up converter dissipates power across the internal N-MOS as the controller ramps up the inductor current. In continuous condition, the power dissipated internally can be approximated by : DRLf DV V VIP ONDS OSC in in OO boost uuu uu ])(12 1)[( w here I O : It is the load current. f OSC : It is a switching frequency. KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 Soft-Start Cycle-by-Cycle Over-Current Protection Over-Voltage Protection Power dissipation consideration

External components of main boost converter can be designed by performing simple calculations. It need to follow regulation by the output voltage and the maximum load current, as well as maximum and minimum input voltages. Begin by selecting an inductor value. Once L is know, choose the diode and capacitors. Inductor selection depends on input voltage, output voltage, maximum current , switching frequency and availability of inductor values. The following boost circuit equations are useful in choosing the inductor values based on the application. They allow the trading of peak current and inductor value while allowing for consideration of component availability and cost. The peak inductor current is given by: D II III O LAVG L LAVGLpeak where: ϦI L is the inductor peak-to-peak current ripple and is decided by: OSC in L f D L VI u ' D is the MOSFET turn on ratio and is decided by: O inO V VVD f OSC is the switching frequency. The inductor should be chosen to be able to handle this current and inductor saturation current rating should be greater than I PEAK The output diode has average current of I O , and peak current the same as the inductor’s peak current and a voltage rating at least 1.5 times the output voltage. Schottky diode is recommended and it should be able to handle those current. The KB4312 is specially compensated to be stable with capacitors which have a worst- case minimum value of 1uF at the particular V OUT being set. Output ripple voltage requirements also determine the minimum value and type of capacitors. Output ripple voltage consists of two components the voltage drop caused by the switching current through the ESR of the output capacitor and the charging and discharging of the output capacitor: OSCOUT O O inO LPEAKRIPPLE fC I V VVESRIV uuu For low ESR ceramic capacitors, the output ripple is dominated by the charging or discharging of the output capacitor. KB4312 Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 Applications Information Boost inductor Diode selection Output Capacitor

Kingbor Technology Co.,Ltd TEL:(86)0755-26508846 FAX:(86)0755-26509052 PACAGE DESCRIPTION Kingbor Technology TEL:(86)0755-26508846 FAX:(86)0755-26509052 www.kingbor.com Small Outline SOT23-6 DIM Millimetres Inches DIM Millimetres Inches Min Max Min Max Min Max Min Max D 2.80 3.00 0.110 0.118 L 0° 10° 0° 10° PACKAGE DIMENSIONS CONTROLLING DIMENSIONS IN MILLIMETRES APPROX CONVERSIONS INCHES. DATUM Aa C E AA 2 D b e PACKAGE OUTLINE PAD LAYOUT DETAILS DIM Millimeters Inches MIN. MAX. MIN. MAX. A 0.90 1.45 0.0354 0.0570 A1 - 0.15 - 0.0059 A2 0.90 1.30 0.0354 0.0511 b 0.20 0.50 0.0078 0.0196 C 0.09 0.26 0.0035 0.0102 D 2.70 3.10 0.1062 0.1220 E 2.20 3.20 0.0866 0.1181 E1 1.30 1.80 0.0511 0.0708 e 0.95 REF 0.0374 REF e1 1.90 REF 0.0748 REF L 0.10 0.60 0.0039 0.0236 a 0° 30° 0° 30° PACKAGE DIMENSIONSPACKAGE OUTLINE Small Outline SOT23-5