AIC1638-30CX

AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00
FEATURES ! ! ! ! ! ! !
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 2.7V, 3.0V, 3.3V, or 5V. The AIC1638 starts up from below 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-92 packages make the AIC1638 an ideal choice of DC/DC converter for space conscious applications, like pagers, electronic cameras, and wireless microphones Guaranteed Start-Up from below 0.9 V. High Efficiency. Low Quiescent Current. Few Number of External Components needed. Low Ripple and Low Noise. Fixed Output Voltage: 2.7V, 3.0V, 3.3V, and 5V. Space Saving SOT-89 and TO-92 Packages.
APPLICATIONS ! ! ! ! ! ! Pagers. Cameras. W ireless Microphones. Pocket Organizers. Battery Backup Suppliers. Portable Instruments.
TYPICAL APPLICATION CIRCUIT VIN + C2 47µF L1 88µH D1 VOUT SW AIC1638-27 AIC1638-30 AIC1638-33 AIC1638-50 GND VOUT + C1 22µF One Cell Step-Up DC/DC Converter ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 1 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00
ORDERING INFORMATION AIC1638- XXX ORDER NUMBER PACKAGE TYPE X: SOT-89 Z: TO-92 TEMPERATURE RANGE C: -20 ° C
+80 ° C OUTPUT VOLTAGE 27: 2.7V 30: 3.0V 33: 3.3V 50: 5.0V AIC1638-27CZ AIC1638-30CZ AIC1638-33CZ AIC1638-50CZ (TO-92) AIC1638-27CX AIC1638-30CX AIC1638-33CX AIC1638-50CX (SOT-89) PIN CONFIGURATION TOP VIEW 1: GND 2: VOUT 3: SW 1 2 3 TOP VIEW 1: GND 2: VOUT 3: SW 1 2 3
 ABSOLUATE MAXIMUM RATINGS Supply Voltage ………………………………………………………………………….12V ……………………………………………………………………0.6A SW pin Voltage ………………………………………….…………………………………….12V SW pin Switch Current Power Dissipation ……………………………………………………..……………….500mW Operating Temperature Range ………………………………..…………….….-20°C to 80 °C Storage Temperature Range ………………………………………………… -65°C to 150 °C Lead Temperature (Sordering 10 Sec.) …………………………………………………260°C
 TEST CIRCUIT AIC1638 2.5V VOUT GND SW 100 FOUT Oscillator Test Circuit ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 2 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " ELECTRICAL CHARACTERISTICS PARAMETER Output Voltage (Ta=25°C, IO=10mA, Unless otherwise specified) SYMBOL TEST CONDITIONS VIN=1.8V VIN=1.8V VIN=2.0V VIN=3.0V MIN. 2.633 2.925 3.218 4.875 TYP. 2.700 3.000 3.300 5.000 MAX. 2.767 3.075 3.382 5.125 8 UNIT V VOUT Input Voltage Start-Up Voltage Min. Hold-on Voltage No-Load Input Current Supply Current IOUT=1mA, VIN:0→2V IOUT=1mA, VIN:2→0V IOUT=0mA VIN=VOUT x 0.95 Measurement of the IC input current VIN VSTART VHOLD IIN IDD1 15 42 50 60 90 7 0.8 V V V µA µA 0.9 0.7 Supply Current VIN=VOUT + 0.5V Measurement of the IC input current IDD2 µA SW Leakage Current SW Switch-On Resistance VSW =10V, VIN=VOUT + 0.5V VIN=VSW x 0.95, VSW =0.4V RON 1.3 1.2 1.1 1 65 75 0.5 µA Ω Oscillator Duty Cycle VIN=VOUT x 0.95 Measurement of the IC input current DUTY 85 % Max. Oscillator Freq. VIN=VOUT x 0.95 Measurement of the IC input current FOSC 80 105 130 KHz Efficiency η 85 % ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 3 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS Capacitor (C1) : 47 µ F (Tantalum Type) Diode (D1) : 1N5819 Schottky Type AIC1638-27 Load Regulation (L=100µH CD54) 2.8 85 AIC1638-27 Efficiency (L=100µH CD54) 2.7 80 Output voltage (V) VIN=1.2V 2.5 Efficiency (%) 2.6 VIN=1.5V VIN=1.8V VIN=2.0V 75 70 VIN=1.8V VIN=2.0V 2.4 65 VIN=1.5V VIN=0.9V 60 2.3 VIN=0.9V 2.2 0 55 20 40 60 80 100 120 140 160 180 0 20 40 60 VIN=1.2V 80 100 120 140 160 180 Output Current (mA) Output current (mA) AIC1638-27 Load Regulation (L=47µH CD54) 2.8 AIC1638-27 Efficiency 85 80 (L=47µH CD54) 2.7 75 Output voltage (V) 2.6 Efficiency (%) VIN=1.2V 2.5 VIN=1.5V VIN=1.8V VIN=2.0V 70 65 60 VIN=2.0V VIN=1.8V 2.4 VIN=1.2V VIN=0.9V VIN=1.5V 55 VIN=0.9V 2.3 0 20 40 60 80 100 120 140 160 180 200 220 240 50 0 20 40 60 80 100 120 140 160 180 200 220 240 Output Current (mA) Output current (mA) 1.0 0.9 0.8 AIC1638-27 Start-Up & Hold-ON Voltage (L=47µH) AIC1638-27 Start-Up & Hold-ON Voltage (L=100µH) 1.0 0.9 Start up 0.8 Start up 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 2 4 6 8 10 12 14 16 18 Input Voltage (V) Input Voltage (V) 0.7 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 2 4 6 8 10 12 14 16 18 Hold on Hold on Output Current (mA)



Output Current (mA) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 4 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-27 Output Voltage vs Temperature 2.78 2.76 AIC1638-27 Switching Frequency vs Temperature 160 140 Output Voltage Vout (V) 2.74 2.72 2.70 2.68 2.66 2.64 2.62 -40 No Load Switching Frequency (kHz) 120 100 80 60 40 20 -40 -20 0 20 40 60 80 100 Temperature (°C) -20 0 20 40 60 80 100 Temperature (°C) AIC1638-27 Maximum Duty Cycle vs Temperature 82 80 1.8 1.6 AIC1638-27 SW On Resistance vs Temperature Maximum Duty Cycle (% ) SW Turn On Resistance ( Ω) 78 76 74 72 70 68 66 -40 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -40 -20 0 Temperature (°C) 20 40 60 80 100 -20 0 20 40 60 80 100 Temperature (°C) AIC1638-27 Supply Current vs Temperature 52 48



AIC1638-30 Load Regulation (L=100µH, CD54) 3.1 3.0 2.9 2.0V 1.5V 1.8V Supply Current IDD1 (uA) 44 40 36 32 28 24 20 -40 Output voltage VOUT(V) 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 0 10 1.2V VIN=0.9V 20 30 40 50 60 70 80 90 100 110 120 130 140 -20 0 20 40 60 80 100 Temperature (°C) Output Current (mA) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 5 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-30 Efficiency (L=100µH, CD54) 85 80 AIC1638-30 Load Regulation (L=47µH CD54) 3.1 3.0 2.9 Output Voltage (V) Efficiency (%) 75 70 65 60 2.8 2.7 2.6 2.5 2.4 2.3 VIN=1.2V VIN=1.5V VIN=1.8V VIN=2.0V 1.8V 2.0V 1.5V 55 50 VIN=0.9V 0 20 40 60 1.2V 80 100 120 140 160 180 VIN=0.9V 0 20 40 60 80 100 120 140 160 180 200 220 2.2 Output Current (mA) Output Current (mA) 85 80 75 AIC1638-30 Efficiency (L=47µH CD54) 1.0 0.9 0.8 AIC1638-30 Start-up & Hold-on Voltage (L=100µH) Start up Input Voltage (V) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Efficiency (%) 70 65 Hold on VIN=2.0V 60 55 VIN=1.8V VIN=1.5V VIN=1.2V 50 75 100 125 150 175 200 225 VIN=0.9V 50 0 25 0.0 0 2 4 6 8 10 12 14 16 18 20 Output Current (mA) Output Current (mA) AIC1638-30 Start-up & Hold-on Voltage (L=47uH) 1.0 0.9 0.8 3.06 AIC1638-30 Output Voltage vs Temperature Start up 3.04 Output Voltage Vout (V) No Load 3.02 3.00 2.98 2.96 2.94 2.92 2.90 -40 Input Voltage (V) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 2 4 6 8 10 12 14 16 18 20 Hold on -20 0 Output Current (mA) Temperature (°C) 20 40 60 80 100 ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 6 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-30 Switching Frequency vs Temperature 160 AIC1638-30 Maximum Duty Cycle vs Temperature 82 Switching Frequency (kHz) Maximum Duty Cycle (%) 140 120 100 80 60 40 20 0 -40 80 78 76 74 72 70 68 66 -40 -20 0 20 40 60 80 100 -20 0 Temperature (°C) Temperature (°C) 20 40 60 80 100 AIC1638-30 SW On Resistance vs Temperature 1.8 1.6 52 48 AIC1638-30 Supply Current vs Temperature SW Turn On Resistance ( Ω) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -40 Supply Current IDD1 (µA) -20 0 20 40 60 80 100 44 40 36 32 28 24 20 -40 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) AIC1638-33 Load Regulation (L=100µH, CD54) 3.4 3.3 3.2 90 AIC1638-33 Efficiency (L=100µH, CD54) VIN=2.0V VIN=1.8V 85 80 Output Voltage (V) Efficiency (%) 3.1 3.0 2.9 2.8 2.7 2.6 2.5 2.4 2.3 0 25 VIN=1.5V VIN=2.0V 75 70 65 60 VIN=1.2V VIN=1.8V VIN=1.2V VIN=0.9V 0 25 50 75 100 VIN=1.5V VIN=0.9V 50 75 100 125 150 175 200 55 50 125 150 175 200 Output Current (mA) Output Current (mA) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 7 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-33 Load Regulation (L=47µH, CD54) 3.4 3.3 3.2 90 85 80 AIC1638-33 Efficiency (L=47µH,CD54) Output Voltage (V) 3.1 3.0 2.9 2.8 2.7 2.6 2.5 2.4 0 25 VIN=1.5V Efficiency (%) VIN=1.8V VIN=2.0V 75 70 65 60 55 50 VIN=2.0V VIN=1.2V VIN=0.9V 50 75 100 125 150 175 200 225 VIN=1.5V VIN=0.9V VIN=1.2V VIN=1.8V 45 40 0 25 50 75 100 125 150 175 200 225 250 Output Current (mA) Output Current (mA) AIC1638-33 Start-up & Hold-on Voltage (L=100µH) 1.1 1.0 3.50 3.45 AIC1638-33 Output Voltage vs Temperature Input Voltage (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 2 4 6 8 10 12 14 16 18 20 Output Voltage Vout (V) 0.9 Start up 3.40 3.35 3.30 3.25 3.20 3.15 3.10 3.05 3.00 -40 -20 0 20 40 No Load Hold on Output Current (mA) Temperature (°C) 60 80 100 AIC1638-33 Switching Frequency vs Temperature 150 140 82 80 AIC1638-33 Maximum Duty Cycle vs Temperature Switching Frequency (kHz) 130 120 110 100 90 80 70 60 50 -40 -20 0 20 40 60 80 100 Maximum Duty Cycle (%) 78 76 74 72 70 68 66 -40 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 8 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-33 SW On Resistance vs Temperature 1.8 60 56 AIC1638-33 Supply Current vs Temperature SW Turn On Resistance (Ω) 1.6 Supply Current IDD1 (µA) -20 0 20 40 60 80 100 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -40 52 48 44 40 36 32 28 24 -40 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) AIC1638-50 Load Regulation ( L=100µH,CD54) 5.5 5.0 100 90 AIC1638-50 Efficiency (L=100µH,CD54) Output Voltage (V) 4.5 4.0 3.5 3.0 Efficiency (%) VIN=2.0V VIN=3.0V 80 70 60 VIN=2.0V VIN=0.9V VIN=3.0V VIN=1.5V 50 40 VIN=1.5V VIN=1.2V VIN=1.2V 2.5 2.0 1.5 VIN=0.9V 30 20 0 50 100 150 200 250 300 350 400 0 50 100 150 200 250 300 350 400 Output Current (mA) Output Current (mA) AIC1638-50 Load Regulation (L=47µH,CD54) 5.5 5.0 90 85 80 AIC1638-50 Efficiency (L=47µH,CD54) Output Voltage (V) 4.5 VIN=2.0V 4.0 3.5 3.0 Efficiency (%) VIN=3.0V 75 70 65 60 55 50 45 VIN=3.0V VIN=1.5V VIN=1.2V VIN=2.0V VIN=0.9V VIN=1.5V VIN=1.2V 100 150 200 250 300 350 400 2.5 VIN=0.9V 2.0 1.5 0 50 100 150 200 250 300 350 400 0 50 Output Current (mA) Output Current (mA) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 9 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) AIC1638-50 Start-up & Hold-on Voltage (L=100µH) 1.8 1.6 5.3 5.2 AIC1638-50 Output Voltage vs Temperature Output Voltage Vout (V) 1.4 5.1 5.0 4.9 4.8 4.7 4.6 4.5 4.4 -40 No Load Input Voltage (V) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 2 4 6 8 10 12 14 16 18 20 Start up Hold on -20 0 20 40 60 80 100 Output Current (mA)
AIC1638-50 Switching Frequency vs Temperature 150 82 80 Temperature (°C) AIC1638-50 Maximum Duty Cycle vs Temperature Switching Frequency (kHz) Maximum Duty Cycle (%) -20 0 20 40 60 80 100 140 130 120 110 100 90 80 70 60 -40 78 76 74 72 70 68 66 64 -40 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) AIC1638-50 SW On Resistance vs Temperature 1.6 100 90 AIC1638-50 Supply Current vs Temperature SW Turn On Resistance (Ω) 1.4 Supply Current IDD1 µA) -20 0 20 40 60 80 100 80 70 60 50 40 30 20 10 -40 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -40 -20 0 20 40 60 80 100 Temperature (°C) Temperature (°C) ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 10 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 " TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VOUT VOUT 50mV/div 20mv/div VIN
 Load Step 50mA/div 0.5V/div Load Transient Response (L=100µH, Co=47µF, VIN=2V)
Line Transient Response
 BLOCK DIAGRAM SW VOUT 1M 1.25V REF. + Enable GND OSC, 100KHz
 PIN DESCRIPTIONS PIN1 : GND PIN2 : VOUT - Ground. Must be low impedance; sorder directly to ground plane. - IC supply pin. Connect VOUT to the regulator output. PIN3 : SW – Internal drain of N-MOSFET switch.
 APPLICATION INFORMATION GENERAL DESCRIPTION AIC1638 PFM (pulse frequency modulation) controller ICs combine a switch mode regulator, 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 ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. ensure start-up with low battery voltage ( 0.8V typ.). Designed to maximize battery life in portable products, and minimize switching losses by only switching as needed service the load. PFM controllers transfer a discrete amount of energy per cycle and regulate the output voltage by modulating switching frequency with the constant www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 11 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 turn-on time. Switching frequency depends on load, input voltage, and inductor value, and it can range up to 100KHz. The SW on-resistance is typically 1 to 1.5 Ω to minimize switch losses. When the output voltage drops, the error comparator enables 100KHz oscillator that turns on the MOSFET around 7.5us and 2.5µs 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. 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 each cycle. Depending on circuit, PFM controller 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. VIN IIN SW + EXT Isw Ico VOUT VEXT IIN IPK ISW ID Charge Co. IOUT TDIS Discharge Co. VSW t Discontinuous Conduction Mode VEXT ID IOUT IIN IPK IV ISW ID IOUT VSW t Continuous Conduction Mode ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 12 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 At the boundary between continuous and discontinuous mode, output current (IOB) is determined by VIN   1 VIN IOB =  TON(1− x )   VOUT + VD  2 L where VD is the diode drop, x = (RON+Rs)Ton/L. RON= Switch turn on resistance, Rs= Inductor DC resistance TON = Switch ON time In the discontinuous mode, the switching frequency (fsw) is fsw = 2(L)(VOUT + VD − VIN)(IOUT) (1+ x
VIN 2 × TON 2 Ron + Rs  Vin   IPK =  Ton)   1 − exp( − L  Ron + Rs   x  VIN   ≅ (TON)1 −  2 L  VIN (Simple losses equation), ≅ TON L where x=(RON+RS)TON/L 1 EL = L × Ipk2 2 Power required from the inductor per cycle must be equal or greater than 1 PL/fSW = (VOUT + VD − VIN)(IOUT)( ) fSW in order for the converter to regulate the output. When loading is over IOB, PFM controller operates in continuous mode. Inductor peak current can be derived from  VOUT + VD − VSW x  −  IOUT + IPK =  VIN − VSW 2   x  VIN − VSW  TON1 −   2L   2  Valley current (Iv) is  VOUT + VD − VSW x   VIN − VSW  Iv =  − IOUT −  × 2L 2 VIN − VSW     x TON1−   2 In the continuous mode, the switching frequency is fsw = 1 TON (VOUT + VD − VSW) (VOUT + VD − VIN) [1+ x ( VIN − VSW )] 2 VOUT + VD − VSW ≅ 1  VOUT + VD − VIN    TON  VOUT + VD − VSW  where Vsw = switch drop and proportion to output current. INDUCTOR SELECTION 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 ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 13 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 Table 1 Indicates resistance and height for each coil. Inductance ( µH ) 22 DS1608 Coilcraft SMT Type (www.coilcraft.com) DO3316 47 Sumida SMT Type CD54 47 100 47 100 33 0.14 0.25 0.50 0.25 0.50 0.11 1.8 0.7 0.5 0.7 0.5 1.2 4.5 47 100 22 Resistance (Ω) 0.10 0.18 0.38 0.08 Rated Current (A) 0.7 0.5 0.3 2.7 5.2 2.9 Height (mm) Power Inductor Type Hold Hold SMT Type PM54 SMT Type PM75 4.5 5.0 CAPACITOR SELECTION A poor choice for a output capacitor can result in poor efficiency and high output ripple. Ordinary aluminum electrolytic, 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 1.25 times greater than a maximum input voltage. DIODE SELECTION Speed, forward drop, and leakage current are the three main consideration in selecting a rectifier diode. Best performance is obtained with Schottky rectifier diode such 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. COMPONENT POWER DISSIPATION Operating in discontinuous mode, power loss in the winding resistance of inductor can be approximate equal to PDL = 2  TON   VOUT + VD   (Rs ) (POUT ) 3 L   VOUT  where POUT=VOUT * IOUT ; Rs=Inductor DC R; ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 14 AIC1638 3-PIN ONE-CELL STEP-UP DC/DC CONVERTER SPEC NO: DS-1638-00 03/01/00 VD = Diode drop. The power dissipated in a switch loss is PDsw = 2  TON   VOUT + VD − VIN   (RON) (POUT ) 3 L  VOUT   The power dissipated in rectifier diode is  VD  PDD =  (POUT)  VOUT 
 PHYSICAL DIMENSION ! SOT-89 (unit: mm) D D1 C A SYMBOL A B C D MIN 1.40 0.36 0.35 4.40 1.62 2.29 MAX 1.60 0.48 0.44 4.60 1.83 2.60 1.50 (TYP.) 3.00 (TYP.) H E D1 E e L e e1 B e1 H L 3.94 0.89 4.25 1.20 SOT-89 MARKING Part No. AIC1638-27 AIC1638-30 AIC1638-33 AIC1638-50 Marking AN27 AN30 AN33 AN50 ! TO-92 (unit: mm) A L C E SYMBOL A C MIN 4.32 MAX 5.33 0.38 (TYP.) e1 D D E e1 L 4.40 3.17 1.27 (TYP.) 12.7 5.20 4.20 - ANALOG INTEGRATIONS CORPORATION 4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. www.analog.com.tw TEL: (8863)577-2500 FAX:(8863)577-2510 15