AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Feature Description The AT1312A/B/C step-up converter drives white •Operating Voltage:2.5V to 6.0V. LEDs with a constant current to provide backlight in •High Operating Frequency: 1MHz cell phones, PDAs, and other hand-held devices. It •High Output Voltage: Up to 16V/23V/28V features allowing series connection of the white LEDs so that the LED currents are identical for •Shutdown Current <1µA uniform brightness. An enable input can be pulsed •16V/23V/28V Output Over-Voltage Protection repeatedly to adjust LED’s brightness. The fast 1.0 •Digital Dimming Control. MHz current-mode PWM control allows for smaller capacitor and inductor. Fault condition protection •Built-in Cycle-by Cycle Current-Limiting. uses cycle-by-cycle current limiting to sense •Built-in Soft-Start Function. maximum inductor current, thermal protection and •0.2V Low Reference Voltage over-voltage protection. Also included soft-start eliminates inrush current during start-up. The 0.2V •Tiny SOT-26 Package low reference voltage minimized the power loss across the current-setting resistor. Application • LED Module • Compact Back Light Module • Constant Current Source The AT1312A/B/C is available in 6-pin SOT-26 packages. Block Diagram Aimtron reserves the right without notice to change this circuitry and specifications. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 1 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Pin Configuration SOT-25 (TOP VIEW) VIN OVP EN 5 6 4 312 1 LX A:1312AX B:1312BX C:1312CX 2 3 GND FB Ordering Information Part number Package Current Limit AT1312AX SOT-26 400mA AT1312AX_GRE SOT-26, Green 400mA OVP Protection 28V 28V AT1312BX SOT-26 AT1312BX_GRE SOT-26, Green 300mA 300mA 23V 23V AT1312CX SOT-26 AT1312CX_GRE SOT-26, Green 200mA 200mA 16V 16V Marking Date Code ,Date Code with one bottom line Date Code ,Date Code with one bottom line Date Code ,Date Code with one bottom line : Date Code *For more marking information, contact our sales representative directly Pin Description 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 4 EN I 5 6 OVP VIN I P Step-Up Regulator Feedback Input. Connect a sense resistor from FB to ground. 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. Over-voltage protection input. Connect to the output. Power supply. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 2 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Absolute Maximum Ratings*1 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 0.6 A Continuous power dissipation (SOT-26 Ta=+25 C) 0.35 W Operating Junction Temperature Range -30 to 85 ℃ Lead Temperature (Soldering 5 sec) 260 ℃ Storage Temperature -65 to 125 ℃ Package Thermal Resistance (ΘJA) 250 Switch Current (ILX) O ESD Susceptibility*2 HBM 2 MM 200 ℃/W KV V 1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2. Device are ESD sensitive. Handling precaution recommended. The Human Body model is a 100pF capacitor discharged through a 1.5KΩ resistor into each pin. Recommended Operation Conditions Parameter Symbol Power supply voltage VIN Operating temperature Top Min. Values Typ. Max. 2.5 ― 6.0 V -20 +25 +85 ℃ Unit 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 3 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Electrical Characteristics (VIN=2.5V, Ta=+25℃, unless otherwise noted) Parameter Symbol Test Condition Min. Typ. Max. Units Operating V IN Range VIN VIN input Voltage 2.5 - 6.0 V Under Voltage Thershold UVLO VIN falling, 100mV hysteresis 2.1 2.2 2.3 V Switch- Off Input Current IIN1 No Switching - 100 120 µA Shutdown Current IIN3 EN=0V - - 1 µA Feedback Reference VFB 0.190 0.2 0.210 V FB Input Bias Current IFB Over-voltage Threshold VOVP - 28 23 16 1 25 18 µA V V V VFB =0.2V VOUT Rising (AT1312A) VOUT Rising (AT1312B) VOUT Rising (AT1312C) Over-voltage Hysteresis OVP Leakage Current 2 IOVP Output Voltage Line Regulation EN=0V 2.5V< VIN <6.0V V - - 1 µA - 0.1 - % Switching Frequency fOSC - 1 - MHz Maximum Duty DMAX - 90 - % Soft-Start charging time tSS 0.05 0.5 - ms - 400 - mA - 300 - mA LX ON Resistance RLX VIN=3.0V,duty cycle=80% , (AT1312A) VIN=3.0V,duty cycle=80% , (AT1312B) VIN=3.0V,duty cycle=80% , (AT1312C) VIN =2.5V, ILX =200mA LX Leakage Current ILeakage VLX =16V/23V/28V, EN=0V - - 5 µA EN Input Current IEN EN=5V - - 1 µA VIH 0.1V hysteresis 2.0 - - V - - 0.8 V - 4 - ms Switching Current Limit EN Input Level ILX VIL EN low Shutdown Delay - 200 - mA - 0.3 - Ω EN Low Cycle Time tCYCL *1 0.05 - 5 ms EN High Cycle Time tCYCH *1 0.05 - 5 ms - 120 - ℃ Thermal Shutdown *1: tCYCL and tCYCH are included rising time and falling time of PWM signal. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 4 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Typical Characteristics Conversion Efficiency L:SR0302 D:RB501-40 Efficiency vs. Vin (3 LED) L:SR0302 D:RB501-40 5 7 Efficiency (%) 0 8 V 3 = n i V , H u 2 2 = L , s D E L 6 H u 2 2 = L , A m 0 2 = o I Efficiency (%) 5 8 H u 0 1 = L , A m 0 2 = o I V 3 = n i V , H u 2 2 = L , s D E L 4 0 7 H u 8 . 6 = L , A m 0 2 = o I V 3 = n i V , H u 2 2 = L , s D E L 3 H u 7 . 4 = L , A m 0 2 = o I 5 6 0 8 8 8 6 8 4 8 8 7 6 7 2 7 0 2 8 0 7 4 7 9 0 9 L=22uH Io=20mA, L=10uH Efficiency (%) Efficiency (%) Io=20mA, Io=20mA, L=6.8uH Io=20mA,L=4.7u 3 4 Vin (V) 6 L:SR0302 D:RB501-40 2 5 Efficiency vs. Vin (6 LED) L:SR0302 D:RB501-40 Efficiency vs. Vin (4 LED) 90 88 86 84 82 80 78 76 74 72 70 4 3 2 0 2 5 1 0 1 5 0 Vin (V) LED CURRENT(mA) H 5 6 90 88 86 84 82 80 78 76 74 72 70 Io=20mA, L=22uH Io=20mA, L=10uH Io=20mA,L=6.8uH Io=20mA,L=4.7uH 2 3 4 Vin (V) 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 5 5 6 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Efficiency vs. Vin (4 LED) L:SR0302 D:RB501-40 90 88 88 86 86 84 84 82 82 Efficiency (%) 90 80 78 78 H u 0 1 = L 70 H u 7 . 4 = L , A m 0 1 = o I H u 7 . 4 = L , A m 0 1 = o I 72 H u 8 . 6 = L , A m 0 1 = o I 74 H u 0 1 = L , A m 0 1 = o I H u 2 2 = L 76 H u 8 . 6 = L , A m 0 1 = o I 72 , A m 0 1 = o I 74 , A m 0 1 = o I 76 80 H u 2 2 = L , A m 0 1 = o I Efficiency (%) Efficiency vs. Vin (6 LED) L:SR0302 D:RB501-40 70 2 3 4 5 6 2 3 4 5 Vin (V) Vin (V) Ch1:LX Ch2:ILX Ch3:Vo Ch1:LX :10V/div , Ch2:ILX: 200mA/div, Ch3: Vo :100mV/div ,0.2uS/div Switching Transient Waveform 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 6 6 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Ch1:FB Ch2:EN Ch1:FB : 200mV/div , Ch2:ENABLE: 2V/div ,0.2mS/div PWM Dimming Control Using the EN Pin Ch1:IIN Ch2:FB Ch3:EN Ch1:IIN : 200mA/div , Ch2:FB: 100mV/div , Ch3:ENABLE:2V/div ,0.5mS/div Start-Up Waveform 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 7 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Application Circuit ※ Use the tantalum capacitor to eliminate inductor noise on output terminal when you want to control dimming function. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 8 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Prevent Emission Caused by White LEDs Leakage 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 9 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Function Description The AT1312 series are 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 16V/23V/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. AT1312 series 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 proportional to 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 1.0 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 components, the device will be built-in internal loop compensation. Enable Control 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 0.7V 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. Dimming Control 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: I LED = 200mV × TON − PWM RSENSE × TS − PWM Where: TON-PWM : On time of PWM signal TS-PWM : A cycle time of PWM signal If dimming control is not required , EN works as a simple on/off control. Drive EN 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 10 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver high to enable the device , or drive EN low for shutdown. Soft-Start 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. Cycle-by-Cycle Over-Current Protection The AT1312 series 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. Over-Voltage Protection If VOUT is above 16V/23V/28V( for AT1312A/B/C) 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 OVP protection circuitry stops the internal N-MOS. When VOUT falls below 14V/21V/26V, IC will automatically recover normal operation. Thermal-Overload Protection Thermal-overload protection limits total power dissipation in the AT1312 series. When the junction temperature exceeds Tj=130 ℃, a thermal sensor activates the thermal protection, which shuts down the IC, allowing the IC to cool. Once the device cools down by 10 ℃, IC will automatically recover normal operation. For continuous operation , do not exceed the absolute maximum junction-temperature rating of Tj=120 ℃. Power dissipation consideration The AT1312 series 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. In continuous condition, the step-up converter power dissipated internally across the internal N-MOS can be approximated by : 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 11 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Pboost = [( I O × VO 2 1 Vin × D 2 ) ] × RDS (ON ) × D ) + ( Vin 12 f OSC × L where IO : It is the load current. fOSC : It is a switching frequency. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 12 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Application Information External components of boost converter can be designed by performing simple calculations. Boost inductor Inductor selection depends on input voltage, output voltage, maximum output 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: I Lpeak = I LAVG + I LAVG = ∆I L 2 IO 1− D where: △IL is the inductor peak-to-peak current ripple and is decided by: V D ∆I L = in × L f OSC D is the MOSFET turn on ratio and is decided by: V −V in D= O VO fOSC 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 IPEAK. Diode selection The output diode has average current of IO, 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. Output Capacitor The AT1312 series are specially compensated to be stable with capacitors which have a worst- case minimum value of 1uF at the particular VOUT 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: V − Vin IO V RIPPLE = I LPEAK × ESR + O × VO C OUT × f OSC For low ESR ceramic capacitors, the output ripple is dominated by the charging or discharging of the output capacitor. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 13 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver PCB layout guidelines Careful printed circuit layout is extremely important to avoid causing parasitical capacitance and line inductance. The following layout guidelines are recommended to achieve optimum performance. • Please the boost converter diode and inductor close to the LX pin and no via. Keep traces short, direct, and wide. • Please ceramic bypass capacitors near the input/output pin. • Locate all feedback sense resistors as close to the feedback pins as possible. • The ground connections of VIN and VOUT should be as close together as possible. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 14 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Small Outline SOT-26 b e E C e1 D r E1 L A A2 A1 SYMBOL A A1 A2 b C D E E1 L e e1 r INCHES MIN 0.035 0.000 0.035 0.010 0.003 0.110 0.102 0.059 0.014 00 MAX 0.057 0.006 0.051 0.020 0.008 0.122 0.118 0.069 0.022 0.037ref 0.075ref 100 MILLIMETERS MIN MAX 0.90 1.45 0.00 0.15 0.90 1.30 0.25 0.50 0.08 0.20 2.80 3.10 2.60 3.00 1.50 1.75 0.35 0.55 0.95ref 1.90ref 00 100 NOTES - - 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 15 AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Reflow Profiles Profile Feature Average ramp-up rate (TL to TP) Preheat -Temperature Min(Tsmin) -Temperature Max (Tsmax) -Time (min to max)(ts) Tsmax to TL -Ramp-up Rate Time maintained above: -Temperature (TL) -Time (tL) Peak Temperature(TP) Time within 5°C of actual Peak Temperature (tP) Ramp-down Rate Time 25°C to Peak Temperature Sn-Pb Eutectic Assembly Large Body Small Body Pkg. thickness Pkg. thickness <2.5mm or Pkg. ≥2.5mm or Pkg. 3 volume <350mm3 volume ≥350mm 3°C/second max. Pb-Free Assembly Large Body Small Body Pkg. thickness Pkg. thickness ≥2.5mm or Pkg. ≥2.5mm or Pkg. 3 volume ≥350mm volume ≥350mm3 3°C/second max. 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds 3°C/second max. 183°C 60-150 seconds 217°C 60-150 seconds 225+0/-5°C 10-30 seconds 240+0/-5°C 10-30 seconds 6°C/second max. 6 minutes max. 245+0/-5°C 10-30 seconds 250+0/-5°C 20-40 seconds 3°C/second max. 8 minutes max. *All temperatures refer to topside of the package, measured on the package body surface. 7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 2/23/2006 REV:1.1 Email: [email protected] 16