AIC1841/2 High Efficiency 1.5X charge Pump For White LEDs Backlighting FEATURES GENERAL DESCRIPTION 1MHz Switching Frequency The AIC1841 and AIC1842 provide 4 and 6 LED 2.7V to 5.5V Input Voltage Range current source outputs with regulated constant Low Shutdown Current: ≦1µA current for uniform intensity. The AIC1841/2 is the Regulated 20mA Full-Scale Output Current low noise, constant frequency charge pump DC/DC converter that uses 1.5X conversion to 32-Position Linear Scale with Digital Control increase efficiency in white LED applications. The High Accuracy Brightness Matching 33% Less Input Current Than Doubler Charge Pump No Inductors Required devices can be used to produce current levels up to 20mA for each output from a 2.7V to 5.5V input. Low external parts counts (two 1 μ F flying capacitors and two small bypass capacitors at VIN, Build-in Soft-Start and OUT) make the AIC1841/2 ideal for small, Current Limit and Over Temperature Protection battery-powered applications. 12-Pin (AIC1841) and 16-Pin (AIC1842) QFN Package EN/SET interface is used to enable, disable and set the LED current for a 32 level logic scale LED brightness control. Built-in current limiting, with APPLICATIONS thermal shutdown provide protection to the Cellular Phones AIC1841/2 against fault conditions. Automatic soft- PDAs start circuitry prevents excessive inrush current during start-up. 1MHz high switching frequency is Digital Still Cameras enable to use tiny external components. Handheld Devices The AIC1841 is available in a 12-pin thin QFN White LED Backlighting package, and the AIC1842 is available in a spacesaving 16-pin QFN package. Analog Integrations Corporation 3A1, No.1 Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw DS-1842P-02 041707 1 AIC1841/2 TYPICAL APPLICATION CIRCUIT VIN 2.7V~5.5V 4 CFLY1 1uF 5 10 Cin 1uF 6 Cout 1uF 11 9 C1+ C2+ C1- C2- VIN D1 OUT D2 EN/SET D3 GND D4 7 8 12 CFLY2 1uF LED1 1 2 3 LED2 LED3 LED4 AIC1841 VIN 2.7V~5.5V 6 CFLY1 1uF 7 14 Cin 1uF 9 Cout 1uF 15 12 8 13 C1+ C2+ C1- C2- VIN D1 OUT D2 EN/SET D3 GND D4 NC D5 NC AIC1842 D6 10 11 16 C FLY2 1uF LED1 LED2 1 LED3 2 3 4 5 LED4 LED5 LED6 2 AIC1841/2 ORDERING INFORMATION PIN CONFIGURATION AIC1841/2XXXXX VIN D1 PACKING TYPE TR: TAPE & REEL BG: BAG EN/SET QFN-12 (only for AIC1841) TOP VIEW 12 11 10 PACKAGE TYPE HD: QFN-12 (3x3x0.9mm) HF: QFN-16 (3x3x0.9mm) HJ: QFN-16 (4x4x0.9mm) D2 1 9 GND (GND) D3 2 7 C2+ OUT C1+ 6 NC D1 Package and Tape & Reel Packing VIN QFN-16 (only for AIC1842) TOP VIEW EN/SET in Green QFN-12 (3x3x0.9mm) 5 C1- 4 G: Green Package Example: AIC1841GHDTR 8 C2- D4 3 16 15 14 13 Type D2 1 11 C2- (GND) 10 C2+ D5 4 9 OUT 5 6 7 8 NC D4 3 C1- Package and Tape & Reel Packing Type D3 2 C1+ in Green QFN-16 (3x3x0.9mm) 12 GND D6 AIC1842GHFTR ABSOLUTE MAXIMUM RATINGS VIN, VOUT, EN/SET to GND ...........................................................................................................6.0V Thermal Resistance θJA (°C/W) ................................................................................................. 48°C/W Operating Temperature Range ........................................................................................ -40°C to 85°C Junction Temperature ...................................................................................................................125°C Storage Temperature Range ......................................................................................... -65°C to 150°C Lead Temperature (Soldering 10s) ...............................................................................................260°C Thermal Resistance Junction to Ambient, RθJA (Assume no ambient airflow, no heatsink) QFN-12/16 (3x3X0.9mm) 48°C /W QFN-16 (4x4X0.9mm) 43°C /W Thermal Resistance Junction to Case, RθJC QFN-12/16 (3x3X0.9mm) 8°C /W QFN-16 (4x4X0.9mm) 8°C /W Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 3 AIC1841/2 ELECTRICAL CHARACTERISTICS (VIN=3.6V, EN/SET = IN, CIN = C1 = C2 = COUT = 1μF, TA=25°C, Unless otherwise specified.) (Note1) PARAMETER TEST CONDITIONS Operating Voltage Undervoltage-Lockout Threshold MIN. 2.7 VIN falling 2.25 Undervoltage-Lockout Hysteresis 2.45 MAX. UNITS 5.5 V 2.60 V 120 Operating Current Active, No Load Current Shutdown Current EN = 0 Output Current Output Current Line Regulation TYP. 1 18 3.0V ≦ VIN ≦ 5.5V, AIC1841 20 -2 mV 2 mA 1 μA 22 mA 2 %/V 3.2V ≦ VIN ≦ 5.5V, AIC1842 LED to LED Current Matching (Note2) AIC1841 3 7 AIC1842 4 8 % Soft-Start Time 400 Switching Frequency 0.75 Enable Threshold Low VIN = 2.7V to 5.5V Enable Threshold High VIN = 2.7V to 5.5V EN/SET Low Time 1 MHz 0.5 V V 0.3 75 50 EN/SET Off Timeout 300 VIN = 5.5V 1.25 1.4 Minimum EN/SET High Time EN/SET Input Leakage μs -1 μs ns 500 μs 1 μA Thermal Shutdown Threshold 150 °C Thermal Shutdown Hysteresis 25 °C Note 1: Specifications are production tested at TA=25°C. Specifications over the -40°C to 85°C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC). Note 2: Current matching define: (ILED1-ILED2) / (ILED1+ILED2), between any two outputs 4 AIC1841/2 TYPICAL PERFORMANCE CHARACTERISTICS VEN VEN Vo Vo VD VD IIN IIN Vin=3.6V Vin=3.6V Fig2: Shutdown Timeout Fig1: Enable Transient Response VIN VIN Vo Vo VD VD Fig3: 80mA load at Vin=3.0V Fig4: 100mA load at Vin=3.0V VIN VIN Vo Vo VD VD Fig5: 80mA load at Vin=3.6V Fig6: 120mA load at Vin=3.6V 5 AIC1841/2 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) V IN V IN Vo Vo VD VD Fig7: 80mA load at Vin=4.2V Fig8: 120mA load at Vin=4.2V EN/SET EN/SET IDIODE IDIODE Fig9: EN/SET Pin 10kHz Clock Transient Fig10: EN/SET Pin 100kHz Clock Transient 1.50 Quiescent Current (mA) EN/SET 1.25 IDIODE 1.00 0.75 0.50 3.0 Fig11: EN/SET Pin 1MHz Clock Transient 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Fig12: Quiescent vs. Supply Voltage 6 AIC1841/2 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 1.250 Quiescent Current (mA) Quiescent Current (mA) 1.5 1.4 1.3 T = 25 OC 1.2 O T = -40 C T = 85 OC 1.1 1.0 0.9 3.5 3.0 4.0 4.5 5.0 1.225 1.200 1.175 1.150 1.125 1.100 -40 5.5 Normalized LED current Shutdown Current (µA) 40 60 80 100 1.10 0.4 0.3 0.2 0.1 -20 0 20 40 60 80 1.05 1.00 0.95 0.90 -40 100 -20 0 20 40 60 80 100 o Temperature ( oC) Fig16: Normalized LED Current vs. Temperature o Temperature ( C) Fig15: Shutdown Current vs. Temperature 1.20 1.20 1.15 1.15 1.10 T = 25 OC 1.05 T = -40 OC 1.00 T = 85 OC 0.95 Frequency (MHz) Frequency (MHz) 20 Temperature ( C) Fig14: Quiescent Current vs. Temperature 0.5 0.90 0 o Input Voltage (V) Fig13: Quiescent Current vs. Input Voltage 0.0 -40 -20 1.10 1.05 1.00 0.95 3.0 3.5 4.0 4.5 5.0 Input Voltage (V) Fig17: Frequency vs. Input Voltage 5.5 0.90 -40 -20 0 20 40 60 80 100 o Temperature ( C) Fig18: Frequency vs. Temperature 7 AIC1841/2 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 80 Vin > 3.4V Vin = 3.2V 100 Vin = 3.0V 80 Vin = 2.7V 60 40 20 0 Vin > 3.2V 70 Output Current (mA) Output Current (mA) 120 Vin = 3.0V 60 50 Vin = 2.7V 40 30 20 10 0 4 8 12 16 20 24 28 0 32 0 4 8 12 16 20 85 Vin = 2.7V Vin = 3.9V Vin = 3.3V 80 Vin = 4.2V Efficiency (%) Vin = 3.6V 90 Efficiency (%) 32 2 LEDs (40mA) Vin = 3.0V 80 VF = 3.75V 75 70 VF = 3.6V 70 65 Vin = 5.0V 0 20 40 60 80 100 60 3.0 120 VF = 3.45V 3.2 3.4 3.6 4.2 6 LEDs (120mA) 4 LEDs (80mA) 80 80 Efficiency (%) 85 85 VF = 3.75V 75 70 60 3.0 4.0 90 90 65 3.8 Supply Voltage (V) Fig22: Efficiency vs. Supply Voltage LED Current (mA) Fig21: Efficiency vs. Supply Current Efficiency (%) 28 90 100 60 24 Digital Code Fig20: 32 Levels Current Setting with 4 LEDs Digital Code Fig19: 32 Levels Current Setting with 6 LEDs VF = 3.6V VF = 3.45V 3.2 75 VF = 3.75V 70 65 3.4 3.6 3.8 4.0 Supply Voltage (V) Fig23: Efficiency vs. Supply Current 4.2 60 3.0 VF = 3.6V VF = 3.45V 3.2 3.4 3.6 3.8 4.0 4.2 Supply Voltage (V) Fig24: Efficiency vs. Supply Voltage 8 AIC1841/2 BLOCK DIAGRAM C1 C2 1uF 1uF C1P OSC C1N C2P C2N VOUT 1.5X CHARGE PUMP COUT 1uF VIN SS UVLO OTP OCP CIN 1uF OVP EN/SET EN & BIAS REFERENCE CURRENT CONTROLLER COUNTER ILED1 ILED2 ILED3 ILED4 ILED5 ILED6 D1 D2 D3 D4 D5 D6 LED1 LED2 LED3 LED4 LED5 LED6 GND 9 AIC1841/2 PIN DESCRIPTIONS OUT: Charge pump output. For the best performance, OUT should bypass a 1µF (min.) low ESR ceramic capacitor with the shortest distance to ground. D1: Current source output. D2: Current source output. D3: Current source output. D4: Current source output. D5: Current source output. (AIC1842 only) D6: Current source output. (AIC1842 only) GND: Ground. Connect GND as close as possible to system ground and to the ground of the input bypass capacitor. VIN: Input supply voltage. Bypass a 1uF (min.) low ESR ceramic capacitor to GND as close to device as possible. The input voltage range is 2.7V to 5.5V. C1+: Flying capacitor 1 positive terminal. C1-: Flying capacitor 1 negative terminal. C2+: Flying capacitor 2 positive terminal. C2-: Flying capacitor 2 negative terminal. NC: No connect. (AIC1842 only) EN/SET: Enable and current set pin. APPLICATION INFORMATION The AIC1841/2 only requires one 1µF ceramic Operation capacitor for CIN, one 1µF ceramic capacitor for The AIC1841/2 is a high efficiency 1.5X charge COUT and two 1uF ceramic capacitors for the pumps intended for WLED backlighting. This kind charge pump flying capacitors. of converter uses capacitors to store and transfer energy. Since the capacitors can’t change to the Efficiency voltage level abruptly, the voltage ratio of VOUT to The efficiency of AIC1841/2 for ideal 1.5X charge VIN is limited. Capacitive voltage conversion is Refer to Fig. 25, during the “on” state of internal pump can be simply defined as: ×I P V V ×I V η = OUT = OUT OUT = OUT OUT = OUT PIN VIN × IIN VIN × 1.5I OUT 1.5VIN clock, Q1, Q4 and Q7 are closed, which charges The actual efficiency will decrease as the result CFLY1 and CFLY2 to 1/2VIN level. During the “off” from internal switching loss. state, Q2, Q3, Q5 and Q6 are closed. The output WLED Current Level Setting obtained by switching a capacitor periodically. voltage is VIN plus VCFLY, that is, 1.5VIN. VIN CIN Q1 Q2 Q3 CFLY1 Q5 Q4 CFLY2 Q6 The AIC1841/2 D1 to D4/D6 are constant current VOUT outputs which source up to 20mA respectively to drive four or six WLEDs. The LED current is set Q7 Fig. 25 The circuit of 1.5X charge pump COUT via serial interface by the EN/SET pin, which is based on a digital sacle. The interface records rising edges of the EN/SET pin, and counts them into 32 current level settings where each code is 0.625mA greater than previous code. Code 1 is 10 AIC1841/2 the lowest current scale, 0.625mA, and Code 32 32nd clock, the LED output returns to state 1. The is full scale, 20mA. The LED current appears EN/SET pin has to remain high to keep the LED linear with each increasing code. The first rising output current to programmed level when the final edge enables the device and sets the LED output clock is input. current to the lowest setting level, 0.625mA. After 20 Code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 18 16 14 ILED(mA) 12 10 8 6 4 2 0 1 3 5 7 11 13 15 17 19 21 23 25 27 29 31 9 Digital Code WLED Current 0.625 1.250 1.875 2.500 3.125 3.750 4.375 5.000 5.625 6.250 6.875 7.500 8.125 8.750 9.375 10.000 Code 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 WLED Current 10.625 11.250 11.875 12.500 13.125 13.750 14.375 15.000 15.625 16.250 16.875 17.500 18.125 18.750 19.375 20.000 st pulse should be later than 1 pulse for a soft start EN/SET Interface time to maintain a correct LED output current level. The EN/SET timing is as the diagram shown The counter can be clocked up to 1MHz, so the below. The first rising edge enables the device intermediate scales are not visible.The EN/SET and sets the LED output current to the lowest has to hold high to keep the output LED current to setting level. The AIC1841/2 reaches full capaciity programmed level when the final clock is input. after typically 400us soft start time. During the soft When the EN/SET keeps a low for the tSHDN start period, multiple clock pulses may be inserted, timeout period or longer, the AIC1841/2 is they will be missed cause the counter of EN/SET shutdown. interface will work after soft start time. The 2 nd EN t (LO) 0.3us to 75us t (SOFT-START) 400us I(LED) SHDN 1BIT 2 3 4 5 6 7 t (HI) >50ns 8 9 10 11 12 . . . . 29 30 31 32 t (SHDN) 300us 1 2 3 4 SHDN Current Setting Diagram 11 AIC1841/2 Open-Circuit Protection To reduce noise and ripple, low ESR ceramic In any cases of open output circuit, the LEDs are capacitor is recommended for CIN and COUT. The disconnected from the circuit or the LEDs are value of COUT determines the amount of output failed, ripple voltage. An output capacitor with larger etc., the output voltage will limit approximately to 5V. value results in smaller ripple. CFLY is critical for the charge pump which affects turn on time. The Thermal Protection When the temperature of device larger CFLY is, the higher output current obtains. exceeds However, large CIN and COUT are required when approximately 150°C, the thermal protection will large CFLY applies. The ratio of CIN (as well as shut the switching down and the temperature will COUT) to CFLY should be approximately 1:1 to reduce afterwards. Once the temperature drops 10:1. below approximately 125°C, the charge pump Layout Considerations switching circuit will re-start. Even though all six outputs shorted to ground at maximum 120mA, Due to the switching frequency and high transient the die temperature will not increase sufficiently to current of AIC1841/2, careful consideration of enable the thermal protection resulting from its PCB layout is necessary. The CIN should be low thermal resistance. connected as close to the IC as possible. The ground of CIN and COUT should be placed as close Capacitor Selection as possible. To achieve the best performance of Four external capacitors, CIN, COUT, CFLY1, and AIC1841/2, minimize the distance between every CFLY2, two determine AIC1841/2 performances. components and also minimize every Optimum performance can be obtained by using connection length with a maximum trace width. low ESR ceramic capacitors. A 1uF ceramic Make sure each device connects to immediate capacitor for all four capacitors is recommended ground plane. for genernal application. Application Example Ⅰ. When using the AIC1841/2 to drive fewer than corresponding LED current still enables. four/six LEDs, keep current output float. The CFLY1 1uF D1 EN/SET D2 VIN D3 NC D4 GND D5 C2- D6 C2+ C1+ OUT C1- NC EN/SET Vbattery Cin 1uF CFLY2 1uF Cout 1uF AIC1842 12 AIC1841/2 Ⅱ.Any combination of output may be connected current source. This feature is useful to drive in parallel to deliver a single power output to pre-wire LED backlight modules, which is drive a LED module. The maximum output connected in parallel structure circuit. current is the sum of parallel-connected LED Module U1 CFLY1 1uF D1 EN/SET EN/SET D2 VIN Vbattery D3 NC D4 GND D5 C2- D6 C2+ C1+ OUT C1- NC Cin 1uF CFLY2 1uF Cout 1uF AIC1842 Enable Enable Display backlight U1 Keypad backlight CFLY1 1uF D1 EN/SET D2 VIN D3 NC D4 GND D5 C2- D6 C2+ C1+ OUT C1- NC EN/SET Vbattery Cin 1uF CFLY2 1uF Cout 1uF AIC1842 13 AIC1841/2 PHYSICAL DIMENSIONS (unit: mm) QFN 12L - 3x3x0.9-0.5mm D D2 11 11 12 1 2 2 E 1 A3 A A1 θ b e INDEX AREA (D/2*E/2) E2 L 12 S Y M B O L QFN 12L-3x3x0.9-0.5mm MILLIMETERS MIN. MAX. A 0.80 1.00 A1 0.00 A3 Note : 1. Refer to JEDEC MO-220 VEED-3. 2. All dimensions are in millimeters, θ is in degrees. 0.05 0.20 REF b 0.18 0.30 D 2.90 3.10 D2 1.50 1.80 E 2.90 3.10 E2 1.50 1.80 e 0.45 0.55 L 0.35 0.45 θ 0 12 14 AIC1841/2 QFN 16L - 3x3x0.9-0.65mm D2 L D 1 2 E 2 b A3 A A1 θ e INDEX AREA (D/2*E/2) E2 1 S Y M B O L QFN 16L-3x3x0.9-0.5mm MILLIMETERS MIN. MAX. A 0.80 1.00 A1 0.00 0.05 A3 Note: 1. Refer to JEDEC MO-220 VEED-4,6,7 2. All dimensions are in millimeters, θ is in degrees. 0.20 REF 0.30 b 0.18 D 2.90 3.10 D2 1.05 1.80 E 2.90 3.10 E2 1.05 1.80 0.50 BSC e L 0.30 0.55 θ 0 14 15 AIC1841/2 QFN 16L - 4x4x0.9-0.65mm D2 L D 1 2 E 2 b A3 A A1 θ e INDEX AREA (D/2*E/2) E2 1 S Y M B O L QFN 16L-4x4x0.9-0.65mm MILLIMETERS MIN. MAX. A 0.80 1.00 A1 0.00 0.05 A3 Note: 1. Refer to JEDEC MO-220 VGGC-2,3,4 2. All dimensions are in millimeters, θ is in degrees. 0.20 REF 0.35 b 0.25 D 3.90 4.10 D2 2.20 2.80 E 3.90 4.10 E2 2.20 2.80 0.65 BSC e L 0.30 0.65 θ 0 14 16 AIC1841/2 Note: Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result from its use. We reserve the right to change the circuitry and specifications without notice. Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 17