D1 GS SS12 AIC AIC AIC AIC VOUT GND. One Cell Step-Up DC/DC Converter

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1 1-Cell, 3-Pin, Step-Up DC/DC Converter FEATURES A Guaranteed Start-Up from less than 0.9 V. High Efficiency. Low Quiescent Current. Less Number of External Components needed. Low Ripple and Low Noise. Fixed Output Voltage:.7V, 3.0V, 3.3V, and 5V. Space Saving Packages: SOT-89 and TO-9. APPLICATIONS Pagers. Cameras. Wireless Microphones. Pocket Organizers. Battery Backup Suppliers. Portable Instruments. DESCRIPTION The AIC1638 is a high efficiency step-up DC/DC converter for applications using 1 to 4 NiMH battery cells. Only three external components are required to deliver a fixed output voltage of.7v, 3.0V, 3.3V, or 5V. The AIC1638 starts up from less than 0.9V input with 1mA load. Pulse Frequency Modulation scheme brings optimized performance for applications with light output loading and low input voltages. The output ripple and noise are lower compared with the circuits operating in PSM mode. The PFM control circuit operating in 100KHz (max.) switching rate results in smaller passive components. The space saving SOT-89 and TO- 9 packages make the AIC1638 an ideal choice of DC/DC converter for space conscious applications, like pagers, electronic cameras, and wireless microphones. TYPICAL APPLICATION CIRCUIT VIN V L1 100µH D1 GS SS1 + C1 µf AIC AIC AIC AIC1638- V + C 47µF GND One Cell Step-Up DC/DC Converter Analog Integrations Corporation 4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan DS TEL: FAX:

2 ORDERING INFORMATION AIC1638-XXCXXX PIN CONFIGURATION PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE X: SOT-89 Z: TO-9 SOT-89 TOP VIEW 1: GND : V 3: 1 3 Example: PUT VOLTAGE 7:.7V 30: 3.0V 33: 3.3V : 5.0V AIC1638-7CXTR.7V Version, in SOT-89 Package & Tape & Reel Packing Type TO-9 TOP VIEW 1: GND : V 3: 1 3 ABSOLUATE MAXIMUM RATINGS Supply Voltage (V pin)..1v pin Voltage..1V pin Switch Current A Operating Temperature Range C to 85 C Storage Temperature Range -65 C to 1 C Lead Temperature (Soldering 10 Sec.) C TEST CIRCUIT AIC V V F GND Oscillator Test Circuit

3 ELECTRICAL CHARACTERISTICS (T A =5 C, I =10mA, Unless otherwise specified) PARAMETER TEST CONDITIONS SYMBOL MIN. TYP. MAX. UNIT Output Voltage AIC AIC AIC AIC1638- V IN =1.8V V IN =1.8V V IN =.0V V IN =3.0V V Input Voltage Normal Operation V IN 8 V Start-Up Voltage I =1mA, V IN :0 V V START 0.9 V Min. Hold-on Voltage I =1mA, V IN : 0V V HOLD 0.7 V No-Load Input Current I =0mA I IN 15 µa Supply Current Supply Current AIC AIC AIC AIC1638- EXT at no load, V IN =V x 0.95 Measurement of the IC input current (V pin) AIC AIC AIC AIC1638- V IN =V + 0.5V Measurement of the IC input current (V pin) I DD1 I DD 4 V 90 µa µa Leakage Current V =10V, V IN =V + 0.5V 0.5 µa Switch-On Resistance Oscillator Duty Cycle Max. Oscillator Freq. AIC AIC AIC AIC1638- V IN =V x 0.95, V =V V IN =V x 0.95 Measurement of the pin waveform V IN =V x 0.95 Measurement of the pin waveform R ON DUTY % 1 F OSC KHz Efficiency η 85 % Ω 3

4 TYPICAL PERFORMANCE CHARACTERISTICS (Refer to Typical Application) Capacitor (C) : 47 µ F (Tantalum Type) Diode (D1) : 1N5819 Schottky Type Output Voltage (V).6 V IN =1.5V V IN =1.8V V IN =.0V V IN =1.V.5.4 V IN =0.9V Fig. 1 AIC Load Regulation (L=100µH CD54) Efficiency (%) V IN =1.5V V IN =1.8V V V IN =1.V IN =0.9V Output current (ma) Fig. AIC Efficiency (L=100µH CD54) V IN =.0V.8 85 Output Voltage (V) VIN=1.V VIN=0.9V V IN=1.5V V IN=1.8V VIN=.0V Fig. 3 AIC Load Regulation (L=47µH CD54) Efficiency (%) VIN=0.9V VIN=1.V VIN=1.5V VIN=1.8V Output current (ma) Fig. 4 AIC Efficiency (L=47µH CD54) VIN=.0V Input Voltage (V) Start up Hold on Input Voltage (V) Start up Hold on Fig. 5 AIC Start-Up & Hold-ON Voltage (L=47µH CD54) Fig. 6 AIC Start-Up & Hold-ON Voltage (L=100µH CD54) 4

5 TYPICAL PERFORMANCE CHARACTERISTICS (Continued).78 1 Output Voltage V(V) No Load Switching Frequency (khz) Fig. 7 AIC Output Voltage vs. Temperature 0 Fig. 8 AIC Switching Frequency vs. Temperature Maximum Duty Cycle (%) Turn On Resistance (Ω) Fig. 9 AIC Maximum Duty Cycle vs. Temperature Fig. 10 AIC Turn On Resistance vs. Temperature Supply Current I DD1 (µa) Fig. 11 AIC Supply Current vs. Temperature Output voltage V(V) V IN=0.9V V IN=1.V V IN=1.5V V IN=.0V VIN=1.8V Fig. 1 AIC Load Regulation (L=100µH, CD54) 5

6 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Efficiency (%) VIN=1.5V V IN=1.8V V IN=.0V Output Voltage (V) VIN=1.V V IN=1.5V VIN=1.8V VIN=.0V 55 VIN=0.9V V IN=1.V.3 V IN=0.9V Fig. 13 AIC Efficiency (L=100µH, CD54) Fig. 14 AIC Load Regulation (L=47µH CD54) Start up Efficiency (%) V IN=1.8V VIN=.0V Input Voltage (V) Hold on 55 V IN=1.5V VIN=0.9V VIN=1.V Fig. 15 AIC Efficiency (L=47µH CD54) Fig. 16 AIC Start-up & Hold-on Voltage (L=100µH CD54) 3.06 Input Voltage (V) Start up Hold on Output Voltage Vout (V) No Load Fig. 17 AIC Start-up & Hold-on Voltage (L=47µH CD54).90 Fig. 18 AIC Output Voltage vs. Temperature 6

7 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 1 8 Switching Frequency (khz) Maximum Duty Cycle (%) Fig. 19 AIC Switching Frequency vs. Temperature 66 Fig. 0 AIC Maximum Duty Cycle vs. Temperature Turn On Resistance (Ω) Fig. 1 AIC Turn On Resistance vs. Temperature Supply Current IDD1 (µa) Fig. AIC Supply Current vs. Temperature Output Voltage (V) V IN=1.V VIN=0.9V VIN=1.5V V IN=1.8V V IN=.0V Fig. 3 AIC Load Regulation (L=100µH, CD54) Efficiency (%) V IN=0.9V VIN=1.V VIN=1.5V VIN=1.8V V IN=.0V Fig. 4 AIC Efficiency (L=100µH, CD54) 7

8 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Output Voltage (V) VIN=0.9V VIN=1.5V V IN=1.V V IN=1.8V V IN=.0V Efficiency (%) VIN=0.9V V IN=1.V V IN=1.5V VIN=1.8V V IN=.0V Fig. 5 AIC Load Regulation (L=47µH, CD54) Fig. 6 AIC Efficiency (L=47µH,CD54) Input Voltage (V) Start up Hold on Fig. 7 AIC Start-up & Hold-on Voltage (L=100µH CD54) Output Voltage Vout (V) No Load 3.00 Fig. 8 AIC Output Voltage vs. Temperature Switching Frequency (khz) Fig. 9 AIC Switching Frequency vs. Temperature Maximum Duty Cycle (%) Fig. 30 AIC Maximum Duty Cycle vs. Temperature 8

9 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Turn On Resistance (O) Fig. 31 AIC Turn On Resistance vs. Temperature Supply Current IDD1 (µa) Fig. 3 AIC Supply Current vs. Temperature Output Voltage (V) V IN=.0V VIN=1.5V V IN=1.V V IN=0.9V V IN=3.0V Efficiency (%) VIN=0.9V VIN=1.V VIN=1.5V V IN=.0V V IN=3.0V Fig. 33 AIC1638- Load Regulation ( L=100µH CD54) Fig. 34 AIC1638- Efficiency (L=100µH CD54) Output Voltage (V) VIN=0.9V V IN=1.V V IN=1.5V VIN=.0V V IN=3.0V Fig. 35 AIC1638- Load Regulation (L=47µH CD54) Efficiency (%) VIN=3.0V 65 VIN=.0V 55 V IN=0.9V V IN=1.5V VIN=1.V Fig. 36 AIC1638- Efficiency (L=47µH CD54) 9

10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Input Voltage (V) Start up Hold on Output Voltage Vout (V) No Load Fig. 37 AIC1638- Start-up & Hold-on Voltage (L=100µH CD) 4.4 Fig. 38 AIC1638- Output Voltage vs. Temperature Switching Frequency (khz) Fig. 39 AIC1638- Switching Frequency vs. Temperature Maximum Duty Cycle (%) Fig. 40 AIC1638- Maximum Duty Cycle vs. Temperature Turn On Resistance (O) 1. Fig. 41 AIC1638- Turn On Resistance vs. Temperature Supply Current I DD1 (µa) Fig. 4 AIC1638- Supply Current vs. Temperature 10

11 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) V V 0mv/div mv/div VIN 100mA 0.5V/div Load Step ma/div Fig. 43 Load Transient Response Fig. 44 Line Transient Response (L 1 =100µH, C =47µF, V IN =V) (L 1 =100µH, C =47µF) BLOCK DIAGRAM V 1.5V REF. 1M - + GND Enable OSC, 100KHz PIN DESCRIPTIONS PIN1 : GND - Ground. Must be low impedance; solder directly to ground plane. PIN : V - IC supply pin. Connect V to the converter output. PIN3 : Internal drain of N-MOSFET switch. 11

12 APPLICATION INFORMATIONS GENERAL DESCRIPTION AIC1638 PFM (pulse frequency modulation) converter ICs combine a switch mode converter, N-channel power MOSFET, precision voltage reference, and voltage detector in a single monolithic device. They offer both extreme low quiescent current, high efficiency, and very low gate threshold voltage to ensure start-up with low battery voltage ( V typ.). Designed to maximize battery life in portable products, and minimize switching losses by only switching as needed service the load. PFM converters transfer a discrete amount of energy per cycle and regulate the output voltage by modulating switching frequency with the constant turn-on time. Switching frequency depends on load, input voltage, and inductor value, and it can range up to 100KHz. The on-resistance is typically 1 to 1.5 Ω to minimize switch losses. each cycle. Depending on circuit, PFM converter can operate in either discontinuous mode or continuous conduction mode. Continuous conduction mode means that the inductor current does not ramp to zero during each cycle. V IN I IN I D I + EXT Isw Ico AIC1638 V EXT V When the output voltage drops, the error comparator enables 100KHz oscillator that turns on the MOSFET around 7.5us and.5µs off time. Turning on the MOSFET allows inductor current to ramp up, storing energy in a magnetic field. When MOSFET turns off that force inductor current through diode to the output capacitor and load. As the stored energy is depleted, the current ramp down until the diode turns off. At this point, inductor may ring due to residual energy and stray capacitance. The output capacitor stores charge when current flowing through the diode is high, and release it when current is low, thereby maintaining a steady voltage across the load. I IN I V I D T DIS Charge Co. Discharge Co. I PK I As the load increases, the output capacitor discharges faster and the error comparator initiates cycles sooner, increasing the switching frequency. The maximum duty cycle ensure adequate time for energy transfer to output during the second half Discontinuous Conduction Mode t 1

13 V EXT [1+ ( V VIN) 1 fsw = TON (V V) x VIN V ( )] V V I IN I PK 1 V VIN TON V V I V where Vsw = switch drop and proportion to output current. I INDUCTOR SELECTION I D I V t Continuous Conduction Mode At the boundary between continuous and discontinuous mode, output current (I OB ) is determined by VIN 1 VIN IOB = TON V L ( 1 x) where V D is the diode drop, x = (R ON +Rs)Ton/L. R ON = Switch turn on resistance, Rs= Inductor DC resistance T ON = Switch ON time In the discontinuous mode, the switching frequency (Fsw) is (L)(V Fsw = V VIN)(I T ON IN ) (1 + x) In the continuous mode, the switching frequency is To operate as an efficient energy transfer element, the inductor must fulfill three requirements. First, the inductance must be low enough for the inductor to store adequate energy under the worst case condition of minimum input voltage and switch ON time. Second, the inductance must also be high enough so maximum current rating of AIC1638 and inductor are not exceed at the other worst case condition of maximum input voltage and ON time. Lastly, the inductor must have sufficiently low DC resistance so excessive power is not lost as heat in the windings. But unfortunately this is inversely related to physical size. Minimum and Maximum input voltage, output voltage and output current must be established before and inductor can be selected. In discontinuous mode operation, at the end of the switch ON time, peak current and energy in the inductor build according to IPK V L Vin Ron + Rs = 1 exp( Ton) Ron + Rs L IN ( T ) ON 1 x VIN TON (Simple losses equation), L where x=(r ON +R S )T ON /L 13

14 1 EL = L Ipk Power required from the inductor per cycle must be equal or greater than PL/F = (V + V D VI N )(I 1 )( F in order for the converter to regulate the output. When loading is over I OB, PFM converter operates in continuous mode. Inductor peak current can be derived from ) I PK V = V IN V VIN V V L T Valley current (Iv) is V Iv = T ON V VIN V 1 x ON x I x 1 x I + V IN V L Table 1 Indicates resistance and height for each coil. Inductance Power Inductor Type ( mh ) Coilcraft SMT Type ( Sumida SMT Type CD54 Hold SMT Type PM54 DS18 DO3316 Resistance ( W ) Rated Current (A) Hold SMT Type PM Height (mm) CAPACITOR SELECTION A poor choice for a output capacitor can result in poor efficiency and high output ripple. Ordinary aluminum electrolyzers, while inexpensive may have unacceptably poor ESR and ESL. There are low ESR aluminum capacitors for switch mode DC-DC converters which work much better than general propose unit. Tantalum capacitors provide still better performance at more expensive. OS-CON capacitors have extremely low ESR in a small size. If capacitance is reduced, output ripple will increase. Most of the input supply is supplied by the input bypass capacitor, the capacitor voltage rating should be at least 1.5 times greater than a maximum input voltage. DIODE SELECTION Speed, forward drop, and leakage current are the three main considerations in selecting a rectifier diode. Best performance is obtained with Schottky rectifier diode, such as 1N5819. Motorola makes MBR0530 in surface mount. For lower output power a 1N4148 can be used although efficiency and start-up voltage will suffer substantially. 14

15 COMPONENT POWER DISSIPATION Operating in discontinuous mode, power loss in the winding resistance of inductor can be approximate equal to PD L = T 3 L ON V + V V D ( Rs ) ( P) where P =V I ; Rs=Inductor DC R; V D = Diode drop. The power dissipated in a switch loss is PDsw = 3 T L ON V + V V D IN ( RON ) ( P) V The power dissipated in rectifier diode is PD D V = V D (P ) PHYSICAL DIMENSION SOT-89 (unit: mm) D D1 A C SYMBOL MIN MAX A B C H E D D L e e1 B E.9. e 1. (TYP.) e (TYP.) H L SOT-89 MARKING Part No. AIC AIC AIC AIC1638- Marking AN7 AN30 AN33 AN 15

16 TO-9 (unit: mm) A L C E SYMBOL MIN MAX A C 0.38 (TYP.) D e1 D E e1 1.7 (TYP.) L