AIC1841/2 High Efficiency 1.5X charge Pump For White LEDs Backlighting

Transcription

1 High Efficiency.5X charge Pump For White EDs Backlighting FEATURES MHz Switching Frequency.7V to 5.5V Input Voltage Range ow Shutdown Current: μa Regulated 0mA Full-Scale Output Current 3-Position inear Scale with Digital Control High Accuracy Brightness Matching 33% ess Input Current Than Doubler Charge Pump No Inductors Required Build-in Soft-Start Current imit and Over Temperature Protection -Pin (AIC84) and 6-Pin (AIC84) QFN Package APPICATIONS Cellular Phones PDAs Digital Still Cameras Handheld Devices White ED Backlighting GENERA DESCRIPTION The AIC84 and AIC84 provide 4 and 6 ED current source outputs with regulated constant current for uniform intensity. The AIC84/ is the low noise, constant frequency charge pump DC/DC converter that uses.5x conversion to increase efficiency in white ED applications. The devices can be used to produce current levels up to 0mA for each output from a.7v to 5.5V input. ow external parts counts (two μ F flying capacitors and two small bypass capacitors at V IN, and OUT) make the AIC84/ ideal for small, battery-powered applications. interface is used to enable, disable and set the ED current for a 3 level logic scale ED brightness control. Built-in current limiting, with thermal shutdown provide protection to the AIC84/ against fault conditions. Automatic softstart circuitry prevents excessive inrush current during start-up. MHz high switching frequency is enable to use tiny external components. The AIC84 is available in a -pin thin QFN package, and the AIC84 is available in a spacesaving 6-pin QFN package. Analog Integrations Corporation 3A, No. i-hsin Rd. I, Science Park, Hsinchu 300, Taiwan DS-84G TE: FAX:

2 TYPICA APPICATION CIRCUIT VIN.7V~5.5V Cin C FY Cout 4 7 C+ C+ 5 8 C- C- 0 VIN D 6 OUT D 9 GND D3 D4 3 AIC84 ED C FY ED ED3 ED4 VIN.7V~5.5V Cin C FY Cout 6 0 C+ C+ 7 C- C- 4 6 VIN D 9 OUT D 5 D3 3 GND D4 8 4 NC D5 3 NC D6 5 AIC84 C FY ED ED ED3 ED4 ED5 ED6

3 ORDERING INFORMATION AIC84/XXXXX PACKING TYPE TR: TAPE & REE BG: BAG PACKAGE TYPE HD: QFN- (3x3x0.9mm) HF: QFN-6 (3x3x0.9mm) HJ: QFN-6 (4x4x0.9mm) G: Green Package PIN CONFIGURATION QFN- (only for AIC84) TOP VIEW D D3 D4 3 Example: AIC84GHDTR in Green QFN- (3x3x0.9mm) Package and Tape & Reel Packing Type AIC84GHFTR in Green QFN-6 (3x3x0.9mm) Package and Tape & Reel Packing Type QFN-6 (only for AIC84) TOP VIEW D D3 D4 D5 D6 C+ C- D VIN NC (GND) GND C- 0 C+ 4 9 OUT NC D VIN 0 (GND) C+ C- OUT 9 GND 8 C- 7 C+ ABSOUTE MAXIMUM RATINGS VIN, VOUT, to GND V Thermal Resistance θ JA ( C/W) C/W Operating Temperature Range C to 85 C Junction Temperature... 5 C Storage Temperature Range C to 50 C ead Temperature (Soldering 0s) C Thermal Resistance Junction to Ambient, Rθ JA (Assume no ambient airflow, no heatsink) QFN-/6 (3x3X0.9mm) 48 C /W QFN-6 (4x4X0.9mm) 43 C /W Thermal Resistance Junction to Case, RθJC QFN-/6 (3x3X0.9mm) 8 C /W QFN-6 (4x4X0.9mm) 8 C /W Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 3

4 EECTRICA CHARACTERISTICS (V IN =3.6V, = IN, C IN = C = C = C OUT = μf, T A =5 C, Unless otherwise specified.) (Note) PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS Operating Voltage V Undervoltage-ockout Threshold V IN falling V Undervoltage-ockout Hysteresis 0 mv Operating Current Active, No oad Current ma Shutdown Current EN = 0 μa Output Current 8 0 ma Output Current ine Regulation 3.0V V IN 5.5V, AIC84 3.V V IN 5.5V, AIC84 - %/V ED to ED Current Matching (Note) AIC AIC % Soft-Start Time 400 μs Switching Frequency MHz Enable Threshold ow V IN =.7V to 5.5V 0.5 V Enable Threshold High V IN =.7V to 5.5V.4 V ow Time μs Minimum High Time 50 ns Off Timeout μs Input eakage V IN = 5.5V - μa Thermal Shutdown Threshold 50 C Thermal Shutdown Hysteresis 5 C Note : Specifications are production tested at T A =5 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 : Current matching define: (I ED -I ED ) / (I ED +I ED ), between any two outputs 4

5 TYPICA PERFORMANCE CHARACTERISTICS V EN V EN Vo Vo V D V D I IN Vin=3.6V I IN Vin=3.6V Fig: Enable Transient Response Fig: Shutdown Timeout V IN V IN Vo Vo V D V D Fig3: 80mA load at Vin=3.0V Fig4: 00mA load at Vin=3.0V V IN V IN Vo Vo V D V D Fig5: 80mA load at Vin=3.6V Fig6: 0mA load at Vin=3.6V 5

6 TYPICA PERFORMANCE CHARACTERISTICS (Continued) V IN V IN Vo Vo V D V D Fig7: 80mA load at Vin=4.V Fig8: 0mA load at Vin=4.V I DIODE I DIODE Fig9: Pin 0kHz Clock Transient Fig0: Pin 00kHz Clock Transient.50 I DIODE Quiescent Current (ma) Fig: Pin MHz Clock Transient Input Voltage (V) Fig: Quiescent vs. Supply Voltage 6

7 TYPICA PERFORMANCE CHARACTERISTICS (Continued).5.50 Quiescent Current (ma) T = -40 O C T = 5 O C T = 85 O C Quiescent Current (ma) Input Voltage (V) Fig3: Quiescent Current vs. Input Voltage Temperature ( o C) Fig4: Quiescent Current vs. Temperature Shutdown Current (μa) Normalized ED current Temperature ( o C) Fig5: Shutdown Current vs. Temperature Temperature ( o oc) Fig6: Normalized ED Current vs. Temperature.5.5 Frequency (MHz) T = 5 O C T = -40 O C T = 85 O C Frequency (MHz) Input Voltage (V) Fig7: Frequency vs. Input Voltage Temperature ( o C) Fig8: Frequency vs. Temperature 7

8 TYPICA PERFORMANCE CHARACTERISTICS (Continued) Output Current (ma) Vin > 3.4V Vin = 3.V Vin = 3.0V Vin =.7V Output Current (ma) Vin > 3.V Vin = 3.0V Vin =.7V Digital Code Fig9: 3 evels Current Setting with 6 EDs Digital Code Fig0: 3 evels Current Setting with 4 EDs Efficiency (%) Vin =.7V Vin = 3.3V Vin = 3.0V Vin = 3.6V Vin = 3.9V Vin = 4.V Vin = 5.0V Efficiency (%) = 3.75V = 3.45V EDs (40mA) = 3.6V ED Current (ma) Fig: Efficiency vs. Supply Current Supply Voltage (V) Fig: Efficiency vs. Supply Voltage EDs (80mA) EDs (0mA) Efficiency (%) = 3.45V = 3.75V = 3.6V Efficiency (%) = 3.45V = 3.75V = 3.6V Supply Voltage (V) Fig3: Efficiency vs. Supply Current Supply Voltage (V) Fig4: Efficiency vs. Supply Voltage 8

9 BOCK DIAGRAM C C CP CN CP CN OSC.5X CHARGE PUMP VOUT COUT VIN UVO SS OTP OCP CIN OVP EN & BIAS REFERENCE CURRENT CONTROER COUNTER IED IED IED3 IED4 IED5 IED6 GND D D D3 D4 D5 D6 ED ED ED3 ED4 ED5 ED6 9

10 PIN DESCRIPTIONS D: Current source output. D: Current source output. D3: Current source output. D4: Current source output. D5: Current source output. (AIC84 only) D6: Current source output. (AIC84 only) C+: Flying capacitor positive terminal. C-: Flying capacitor negative terminal. C+: Flying capacitor positive terminal. C-: Flying capacitor negative terminal. OUT: Charge pump output. For the best performance, OUT should bypass a μf (min.) low ESR ceramic capacitor with the shortest distance to ground. 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 (min.) low ESR ceramic capacitor to GND as close to device as possible. The input voltage range is.7v to 5.5V. : Enable and current set pin. NC: No connect. (AIC84 only) APPICATION INFORMATION Operation The AIC84/ is a high efficiency.5x charge pumps intended for WED backlighting. This kind of converter uses capacitors to store and transfer energy. Since the capacitors can t change to the voltage level abruptly, the voltage ratio of V OUT to V IN is limited. Capacitive voltage conversion is obtained by switching a capacitor periodically. Refer to Fig. 5, during the on state of internal clock, Q, Q 4 and Q 7 are closed, which charges C FY and C FY to /V IN level. During the off state, Q, Q 3, Q 5 and Q 6 are closed. The output voltage is V IN plus V CFY, that is,.5v IN. V IN C IN Q Q Q3 Q6 C FY Q4 Q5 C FY Q7 Fig. 5 The circuit of.5x charge pump V OUT C OUT The AIC84/ only requires one µf ceramic capacitor for C IN, one µf ceramic capacitor for C OUT and two ceramic capacitors for the charge pump flying capacitors. Efficiency The efficiency of AIC84/ for ideal.5x charge pump can be simply defined as: POUT VOUT IOUT VOUT IOUT VOUT η = = = = P V I V.5I.5V IN IN IN IN OUT The actual efficiency will decrease as the result from internal switching loss. WED Current evel Setting The AIC84/ D to D4/D6 are constant current outputs which source up to 0mA respectively to drive four or six WEDs. The ED current is set via serial interface by the pin, which is based on a digital sacle. The interface records rising edges of the pin, and counts them into 3 current level settings where each code is 0.65mA greater than previous code. Code is IN 0

11 the lowest current scale, 0.65mA, and Code 3 is full scale, 0mA. The ED current appears linear with each increasing code. The first rising edge enables the device and sets the ED output current to the lowest setting level, 0.65mA. After 3 nd clock, the ED output returns to state. The pin has to remain high to keep the ED output current to programmed level when the final clock is input. IED(mA) Digital Code Code WED Current Code WED Current Interface The timing is as the diagram shown below. The first rising edge enables the device and sets the ED output current to the lowest setting level. The AIC84/ reaches full capaciity after typically 400us soft start time. During the soft start period, multiple clock pulses may be inserted, they will be missed cause the counter of interface will work after soft start time. The nd pulse should be later than st pulse for a soft start time to maintain a correct ED output current level. The counter can be clocked up to MHz, so the intermediate scales are not visible.the has to hold high to keep the output ED current to programmed level when the final clock is input. When the keeps a low for the tshdn timeout period or longer, the AIC84/ is shutdown. EN t (SOFT-START) 400us I(ED) BIT SHDN t (O) 0.3us to 75us t (HI) >50ns t (SHDN) 300us 4 SHDN Current Setting Diagram

12 Open-Circuit Protection In any cases of open output circuit, the EDs are disconnected from the circuit or the EDs are failed, etc., the output voltage will limit approximately to 5V. Thermal Protection When the temperature of device exceeds approximately 50 C, the thermal protection will shut the switching down and the temperature will reduce afterwards. Once the temperature drops below approximately 5 C, the charge pump switching circuit will re-start. Even though all six outputs shorted to ground at maximum 0mA, the die temperature will not increase sufficiently to enable the thermal protection resulting from its low thermal resistance. Capacitor Selection Four external capacitors, C IN, C OUT, C FY, and C FY, determine AIC84/ performances. Optimum performance can be obtained by using low ESR ceramic capacitors. A ceramic capacitor for all four capacitors is recommended for genernal application. To reduce noise and ripple, low ESR ceramic capacitor is recommended for C IN and C OUT. The value of C OUT determines the amount of output ripple voltage. An output capacitor with larger value results in smaller ripple. C FY is critical for the charge pump which affects turn on time. The larger C FY is, the higher output current obtains. However, large C IN and C OUT are required when large C FY applies. The ratio of C IN (as well as C OUT ) to C FY should be approximately : to 0:. ayout Considerations Due to the switching frequency and high transient current of AIC84/, careful consideration of PCB layout is necessary. The C IN should be connected as close to the IC as possible. The ground of C IN and C OUT should be placed as close as possible. To achieve the best performance of AIC84/, minimize the distance between every two components and also minimize every connection length with a maximum trace width. Make sure each device connects to immediate ground plane. Application Example Ⅰ. When using the AIC84/ to drive fewer than four/six EDs, keep current output float. The corresponding ED current still enables. D D D3 D4 VIN NC GND Vbattery Cin CFY D5 C- D6 C+ C+ OUT C- NC AIC84 CFY Cout

13 Ⅱ.Any combination of output may be connected in parallel to deliver a single power output to drive a ED module. The maximum output current is the sum of parallel-connected current source. This feature is useful to drive pre-wire ED backlight modules, which is connected in parallel structure circuit. ED Module U D D D3 VIN NC Vbattery Cin D4 GND CFY D5 C- D6 C+ C+ OUT C- NC AIC84 CFY Cout Enable Display backlight U D D D3 VIN NC Vbattery Cin Enable Keypad backlight D4 D5 D6 GND C- C+ CFY CFY C+ OUT C- NC AIC84 Cout 3

14 PHYSICA DIMENSIONS (unit: mm) QFN - 3x3x mm D D E INDEX AREA (D/*E/) b A3 A A E θ e Note :. Refer to JEDEC MO-0 VEED-3.. All dimensions are in millimeters, θ is in degrees. b D D E E e θ S Y M B O A A A3 QFN -3x3x mm MIIMETERS MIN. MAX REF

15 QFN 6-3x3x mm D D E θ INDEX AREA (D/*E/) b A3 A A E e Note:. Refer to JEDEC MO-0 VEED-4,6,7. All dimensions are in millimeters, θ is in degrees. b D D E E e θ S Y M B O A A A3 QFN 6-3x3x mm MIIMETERS MIN. MAX REF BSC

16 QFN 6-4x4x mm D D θ INDEX AREA (D/*E/) b A3 A A E E e Note:. Refer to JEDEC MO-0 VGGC-,3,4. All dimensions are in millimeters, θ is in degrees. S Y M B O A A A3 b D D E E e θ QFN 6-4x4x mm MIIMETERS MIN. MAX REF BSC

17 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. ife Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. ife 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. 7