AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications General Description Features The AAT3113/4 are low noise, constant frequency charge pump DC/DC converters that use fractional (1.5X) conversion to increase efficiency in White LED applications. The 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 1µF flying capacitors and two small bypass capacitors at VIN, and OUT) make the AAT3113/4 ideally suited for small battery-power applications. • • • • • • • • AnalogicTech™’s Simple Serial Control™ (S2Cwire™) interface is used to enable, disable and set the LED drive current for a 32 level logarithmic scale LED brightness control. The AAT3113/4 have a thermal management system to protect the device in the event of a short circuit condition on any of the output pins. Built-in softstart circuitry prevents excessive inrush current during start-up. High switching frequency enables the use of small external capacitors. A low current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1µA. The AAT3113 provides 4 LED current source outputs, and the AAT3114 provides 6. The AAT3113/4 are available in 16-pin quad QFN packages, and the AAT3113 is also available in the 12-pin TSOPJW package. • • • • • • • • • • ChargePump™ White LED Backlighting AAT3113 - 4 Outputs AAT3114 - 6 Outputs 20mA Full Scale Current 32 Position Logarithmic Scale with Digital Control Simple Serial Control™ (S2Cwire™) interface Low Noise Constant Frequency Operation 33% Less Input Current Than Doubler Charge Pump High Accuracy Brightness Matching Small Application Circuit Regulated Output Current Automatic Soft-Start VIN Range: 2.7V to 5.5V No Inductors 600kHz Switching Frequency Iq < 1µA in Shutdown Temperature Range -40 to 85°C. 16-Pin QFN, 12-Pin TSOPJW Package Applications • • White LED Backlighting Programmable Current Source Typical Application VIN C1+ C1 1µF C1C2+ VOUT VBATTERY CIN 1µF COUT 1µF AAT3114 C2 1µF C2- EN/SET EN/SET GND D1 D2 D3 D4 D5 D6 D6 3113.2004.07.1.4 D5 D4 D3 D2 D1 1 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Pin Descriptions Pin # QFN44-16 TSOPJW-12 Symbol Function 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 7 6 5 N/A N/A 4 3 N/A 2 1 12 11 N/A 10 9 8 D2 D3 D4 D5 D6 C1+ C1NC OUT C2+ C2GND NC VIN EN/SET D1 Current source output Current source output Current source output Current source output (3114 option only) Current source output (3114 option only) Flying Capacitor 1 + terminal Flying Capacitor 1 - terminal No Connect Charge pump output. Requires 1uF bypass capacitor to ground. Flying Capacitor 2 + terminal Flying Capacitor 2 - terminal Ground No Connect Input power supply. Requires 1uF bypass capacitor to ground. Control Pin using S2Cwire serial interface. Current source output 1. Required reference current source. Part Number Descriptions Part Number AAT3113-20 AAT3114-20 Function 4 Diode outputs, 20mA full scale 6 Diode outputs, 20mA full scale Pin Configuration 12-Lead TSOPJW (Top View) 5 8 6 7 D3 2 D4 3 (D5) 4 AAT3113/4 12 GND 11 C2- 10 C2+ 9 OUT 8 7 6 5 NC C1- C1+ (D6) 2 13 9 1 14 10 4 D2 NC VIN 3 C2GND VIN EN/SET D D 15 11 EN/SET 12 2 16 1 D1 C2+ OUT C1C1+ D D 16 LD 4x4mm QFN (Top View) 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Absolute Maximum Ratings Symbol VIN VOUT VEN/SET VEN/SET(MAX) IOUT θJA TJ (TA=25°C unless otherwise noted) Description Input Voltage Charge Pump Output EN/SET to GND Voltage Maximum EN/SET to Input Voltage Maximum DC Output Current (Sum of Iout and D currents) Thermal Resistance Operating Junction Temperature Range Value Units -0.3 to 6 -0.3 to 6 -0.3 to 6 0.3 150 37 -40 to 150 V V V V mA °C/W °C Electrical Characteristics VIN=3.5V, TA = -40 to 85°C unless otherwise noted. Typical values are at TA = 25°C. Symbol Description Input Power Supply VIN Operation Range ICC Operating Current ISHDN Shutdown Current IDX ∆ID/∆VIN I(D-Match) η Charge Pump tSS FCLK EN/SET VEN(L) VEN(H) tLO tHI tOFF Input Current 3113.2004.07.1.4 Output Current Output Current Line Regulation Current Matching between any two outputs Efficiency Conditions Min Typ Max Units 2.7 Active, No Load Current EN=0 3113: 3.0 ≤ VIN ≤ 5.5 TA = 25°C, All 3114: 3.2 ≤ VIN ≤ 5.5 Outputs Max Current 3.0 ≤ VIN ≤ 5.5 18 1 5.5 2 1 V mA µA 20 22 mA 2 %/V -2 VD1:Dn=3.6, VIN=3.3V 0.3 % VIN=3.5, IOUT(total)=40mA 93 % 400 600 µs KHz Soft start time Clock Frequency Enable Threshold Low VIN = 2.7 to 5.5V Enable Threshold High VIN = 2.7 to 5.5V EN/SET low time Minimum EN/SET high time EN/SET Off Timeout EN/SET input leakage VIN = 5.5V 300 900 0.5 1.4 0.3 75 50 300 -1 500 1 V V µs ns µs µA 3 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Typical Characteristics (unless otherwise noted: VIN=3.5V, CIN=COUT=C1=C2=1µF, TA=25°C) Quiescent Current vs. Temperature Efficiency vs. Supply Voltage 100% 30 mA 1.000 95% 0.980 90% Efficiency 0.960 IQ (mA) 20 mA 0.940 0.920 85% 40 mA 80% 75% 0.900 120 mA 70% 0.880 65% 0.860 60% 3.0 -40 -20 0 20 40 60 80 100 3.2 3.4 4.0 4.2 4.4 96% 1.2 94% Efficiency (%) 1.1 1.0 IQ (mA) 3.8 Efficiency vs. Load Current Quiescent Current vs. Supply Voltage 0.9 0.8 92% 90% 88% 86% 84% 82% 0.7 80% 0.6 3.0 3.5 4.0 4.5 5.0 0 5.5 20 40 60 80 100 120 Load Current (mA) Supply Voltage (V) Shutdown Current vs. Temperature Oscillator Frequency vs. Temperature 1.000 710 700 690 680 0.100 FOSC (kHz) Shutdown Current (µA) 3.6 Supply Voltage (V) Temperature (°C) 0.010 670 660 650 640 630 0.001 -40 620 -20 0 20 40 Temperature (°C) 4 60 mA 80 mA 60 80 100 610 -40 -20 0 20 40 60 80 100 Temperature (°C) 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Typical Characteristics (unless otherwise noted: VIN=3.5V, CIN=COUT=C1=C2=1µF, TA=25°C) Normalized I DIODE vs. Temperature IDIODE Response -31dB to 0dB 1.020 1.010 ENSET (2V/div) IDIODE 1.000 0.990 0 dB 0.980 0.970 IDIODE 0.960 -31 dB 0.950 -40 -20 0 20 40 60 80 100 10 µs/div Temperature (°C) IDIODE vs. VIN IDIODE Response -9dB to -10dB 140 IDIODE (mA) 120 ENSET (2V/div) 100 80 0 dB 60 -10 dB 40 IDIODE 20 -9 dB 0 3.0 3.5 4.0 -31 dB 4.5 10 µs/div VIN (V) VIH and VIL vs. VIN 140 1.000 120 0.975 0.950 VIH and VIL (V) IDIODE (mA) IDIODE vs. VDIODE 100 80 60 40 0.925 0.900 VIH 0.875 0.850 0.825 VIL 0.800 0.775 20 0 0.750 3.0 3.2 3.4 3.6 V DIODE (V) 3113.2004.07.1.4 3.8 4.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN (V) 5 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Typical Characteristics (unless otherwise noted: VIN=3.5V, CIN=COUT=C1=C2=1µF, TA=25°C) Turn-On Turn-Off ENSET (2V/div) ENSET (2V/div) OUT (5V/div) OUT (5V/div) VDIODE (5V/div) VDIODE (2V/div) IIN (50mA/div) IIN (50mA/div) 100µs/div 200µs/div 60mA Load Characteristics 40mA Load Characteristics IN OUT 20mV/div 10mV/div OUT IN VDIODE VDIODE 1µs/div 1µs/div 120mA Load Characteristics 80mA Load Characteristics 20mV/div OUT OUT VDIODE VDIODE 1µs/div 6 20mV/div IN IN 1µs/div 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Functional Block Diagram VIN Soft Start C1+ C1- 1.5X Charge Pump 600kHz Oscillator C2+ C2- Voltage Reference EN/SET S2Cwire Interface 5 32x8 bit ROM GND Functional Description The AAT3113/4 is a high efficiency 1.5X fractional charge pump device intended for white LED back light applications. The fractional charge pump consists of a linear regulator followed by a 1.5X charge pump. The AAT3113/4 requires only four external components: two 1µF ceramic capacitors for the charge pump flying capacitors (C1 and C2), one 1µF ceramic capacitor for CIN, and one 0.33µF to 1µF ceramic capacitor for COUT. The charge pump output is converted into four or six constant current outputs (D1 to D4 or D6) to drive four or six individual LEDs with a maximum of 20mA each. The current source output magnitude is controlled by the EN/SET serial data S2C interface. The interface records rising edges of the EN/SET pin, and 3113.2004.07.1.4 OUT 8 Current Mode DAC D1 D2 D3 D4 D5* D6* * AAT3114 only decodes them into 32 individual current level settings each 1dB apart (see Current Level Settings below). Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to state 1 after the 32nd clock. With each EN/SET pulse, the output current increases by 1dB. To decrease the output current by 1dB, 31 EN/SET clock pulses are required. The counter can be clocked at speeds up to 1Mhz, so intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to -31dB, the lowest setting equal to 525µA. Once the final clock cycle is input for the desired brightness level, the EN/SET pin is held high to maintain the device output current at the programmed level. The device is disabled 500µs after the EN/SET pin transitions to a logic low state. 7 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Applications Information Current Level Settings LED current level is set via the serial interface according to a logarithmic scale where each code is 1dB greater than the previous code. In this manner, the LED brightness appears linear with each increasing code. Normalized Current Level Settings Normalized Current to Full Scale 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Code Current Levels (mA) 8 Code 20 mA max Code 20 mA max 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0.549 0.627 0.706 0.784 0.863 1.020 1.098 1.255 1.412 1.569 1.804 1.961 2.275 2.510 2.824 3.137 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 3.529 4.000 4.471 5.020 5.647 6.353 7.059 7.922 8.941 10.039 11.216 12.627 14.118 15.843 17.804 20.000 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications EN/SET Serial Interface EN/SET pin is held high to maintain the device output current at the programmed level. The device is disabled 500µs after the EN/SET pin transitions to a logic low state. The current source output magnitude is controlled by the EN/SET pin using AnalogicTech’s Simple Serial Control (S2Cwire) interface. The interface records rising edges of the EN/SET pin, and decodes them into 32 individual current level settings each 1dB apart. Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to state 1 after the 32nd clock, so 1dB of attenuation is achieved by clocking the EN/SET pin 31 times (see graph titled “IDIODE Response -9dB to -10dB” on page 5). The counter can be clocked at speeds up to 1Mhz, so intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to -31dB, the lowest setting equal to 525µA. Once the final clock cycle is input for the desired brightness level, the The EN/SET timing is designed to accommodate a wide range of data rates. After the first rising edge of EN/SET, the charge pump is enabled and reaches full capacity after the soft start time (tSS). During the soft start time, multiple clock pulses may be entered on the EN/SET pin to set the final output current level with a single burst of clocks. Alternatively, the EN/SET clock pulses may be entered one at a time to gradually increase the LED brightness over any desired time period. A constant current is sourced as long as EN/SET remains in a logic high state. The current source outputs are switched off after EN/SET has remained in a low state for at least the tOFF timeout period. EN/SET Timing tLO tHI tOFF EN/SET Code OFF 1 LED Selection The AAT3113/4 devices are designed to drive white LEDs with forward voltages of less than 4.2V. Since the D1:D6 output current sources are matched with negligible voltage dependence, the LED brightness will be matched regardless of their forward voltage matching. Charge Pump Efficiency The AAT3113/4 is a fractional charge pump. The efficiency (η) can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and a half times the input voltage. Efficiency (η) for an ideal 1.5x charge pump can typically be expressed as the output power divided by the input power. η = POUT / PIN 3113.2004.07.1.4 2 3 OFF In addition, with an ideal 1.5x charge pump, the output current may be expressed as 2/3 of the input current. The expression to define the ideal efficiency (η) can be rewritten as: η=POUT/PIN=(VOUTxIOUT)/(VINx1.5IOUT)=VOUT/1.5VIN η(%) = 100(VOUT / 1.5VIN) For a charge pump with an output of 5 volts and a nominal input of 3.5 volts, the theoretical efficiency is 95%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%. These figures are in close agreement for output load conditions from 1mA to 100mA. Efficiency will decrease as load current drops below 0.05mA or when level of VIN approaches VOUT. Refer to the Typical Characteristics section for measured plots of efficiency versus input voltage and output load current for the given charge pump output voltage options. 9 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Power Efficiency and Device Evaluation: Capacitor Characteristics The charge pump efficiency discussion of the previous section only accounts for the efficiency of the charge pump section itself. Due to the unique circuit architecture and design of the AAT3113/14, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3113/14 outputs are pure constant current sources, it is difficult to measure the output voltage for a given output (D1 to D6) to derive an output power measurement. For any given application, white LED forward voltage levels can differ, yet the output drive current will be maintained as a constant. This makes quantifying output power a difficult task when taken in the context of comparing to other white LED driver circuit topologies. A better way to quantify total device efficiency is to observe the total input power to the device for a given LED current drive level. The best White LED driver for a given application should be based on trade-offs of size, external component count, reliability, operating range and total energy usage...Not just "% efficiency". Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3113/4 products. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is lowest cost, has a smaller PCB footprint and is non-polarized. Low ESR ceramic capacitors help maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage. Ceramic Capacitor Materials: Ceramic capacitors less than 0.1µF are typically made from NPO or COG materials. NPO and COG materials typically have tight tolerance and are stable over temperature. Large capacitor values are typically composed of X7R, X5R, Z5U or Y5V dielectric materials. Large ceramic capacitors, typically greater than 2.2µF are often available in low cost Y5V and Z5U dielectrics, but large capacitors are not required in the AAT3113/4 application. AAT3114 Input Power vs. LED Current 700 VIN = 3.6V Input Power (mW) 600 500 400 300 200 100 0 0 20 40 60 80 100 120 140 Output (LED) Current (mA) Capacitor Selection Careful selection of the four external capacitors CIN, C1, C2, COUT is important because they will affect turn on time, output ripple and transient performance. Optimum performance will be obtained when low ESR (<100mΩ) ceramic capacitors are used. In general, low ESR may be defined as less than 100mΩ. A capacitor value of 1µF for all four capacitors is a good starting point when choosing capacitors. If the LED current sources are only programmed for minimal current levels, then the capacitor size may be decreased. 10 Equivalent Series Resistance (ESR): ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor, which is caused by the leads, internal connections, size or area, material composition and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when compared to an equivalent material smaller capacitor. These larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size. Thermal Protection The AAT3113/4 have a thermal protection circuit that will shut down the charge pump and current outputs if the die temperature rises above the thermal limit. However, thermal resistance of the QFN package is so low, that if, in the case of the AAT3114, all six outputs are shorted to ground at maximum 20mA output level, the die temperature will not rise sufficiently to trip the thermal protection. The thermal protection will only trip if COUT is shorted to ground and the ambient temperature is high. 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Application Circuits Typical AAT3113 Application Circuit: VIN C1+ C1 1µF C1C2+ VOUT CIN 1µF VBATTERY COUT 1µF AAT3113 C2 1µF C2- EN/SET EN/SET D1 D2 D3 D4 GND THI > 50ns ON/1 2 3 D4 300ns < TLO < 75µs 4 5 6 D3 D2 D1 50ns minimum to enable n (n < =32) OFF Enable / Disable / LED Brightness Level Set Data Input 3113.2004.07.1.4 11 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Driving White LED display module back lights and individual white LED's connected in parallel: parallel connected. This feature is particularly useful to power pre-manufactured display modules which are pre-wired with white LED backlights connected in a parallel circuit configuration. All output may be connected in parallel to drive groups of LED's as well. The internal current source reference circuit bases feedback from current sensed on the D1 output. For best operation, the only requirement for this application is the output D1 should always be connected to the load circuit. The AAT3113/14 D1 to D6 outputs are true constant current sources capable of driving up to 20mA each over the operation input voltage range. Since these outputs are true constant current sources, they may be connected in parallel to drive a single power output. Any combination of outputs (D1 to D6) may be connected in parallel. The maximum total output current is a sum of how many current sources are AAT3114 application driving a display module with six parallel connected white LEDs: VIN C1+ C1 1µF C1C2+ VOUT V BATTERY CIN 1µF COUT 1µF AAT3114 C2 1µF C2- EN/SET EN/SET D1 D2 D3 D4 D5 D6 Display Module D1 D2 D3 D4 D5 R R D6 GND R R R R Resistor R is optional AAT3114 Dual Backlight Control Circuit: VIN C1+ C1 1µF C1C2+ VOUT V BATTERY CIN 1µF COUT 1µF AAT3114 C2 1µF C2- EN/SET EN/SET GND Keyboard Backlight D1 D2 D3 D4 D5 D6 Display Backlight D4 D1 D2 D5 D6 D3 Enable Keyboard Backlight Enable Display Backlight 12 3113.2004.07.1.4 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications Ordering Information Package Marking1 Part Number (Tape and Reel) QFN44-16 EUXYY AAT3113ISN-20-T1 QFN44-16 FGXYY AAT3114ISN-20-T1 TSOPJW-12 HTXYY AAT3113ITP-20-T1 Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code. Package Information 0.330 ± 0.050 Pin 1 Identification 13 16 0.650 BSC 1 R0.030Max 4 9 8 4.000 ± 0.050 2.400 ± 0.050 5 2.280 REF Top View 0.0125 ± 0.0125 Bottom View 0.203 ± 0.025 0.900 ± 0.050 4.000 ± 0.050 Pin 1 Dot By Marking 0.450 ± 0.050 0.600 ± 0.050 QFN44-16 Side View All dimensions in millimeters. 3113.2004.07.1.4 13 AAT3113/4 High Efficiency 1.5X Fractional Charge Pumps For White LED Applications TSOPJW-12 2.85 ± 0.20 2.40 ± 0.10 0.10 0.20 +- 0.05 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 7° NOM 0.055 ± 0.045 0.04 REF 0.15 ± 0.05 + 0.10 1.00 - 0.065 0.9625 ± 0.0375 3.00 ± 0.10 4° ± 4° 0.45 ± 0.15 0.010 2.75 ± 0.25 All dimensions in millimeters. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 14 3113.2004.07.1.4