GS SS14 AIC AIC AIC AIC EXT GND. 100mA Load Current Step-Up Converter

Transcription

1 1-Cell, 3-Pin, Step-Up DC/DC Controller FEATURES A Guaranteed Start-Up from less than 0.9 V. High Efficiency. ow Quiescent Current. ess Number of External Components needed. ow Ripple and ow Noise. Fixed Output Voltage: 2.7, 3.0V, 3.3V, and 5V. Driver for External Transistor. Space Saving package: SOT-89 and TO-92. APPICATIS Pagers. Cameras. Wireless Microphones. Pocket Organizers. Battery Backup Suppliers. Portable Instruments. TYPICA APPICATI CIRCUIT V IN D1 DESCRIPTI The AIC1639 is a high efficiency step-up DC/DC controller for applications using 1 to 4 battery cells. Only three external components are required to deliver a fixed output voltage of 2.7, 3.0V, 3.3V, or 5V. The AIC1639 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- 92 packages make the AIC1639 an ideal choice of DC/DC controller for space conscious applications, like pagers, electronic cameras, and wireless microphones. Provided with an external transistor driver pin (EXT), the AIC1639 is recommended for applications requiring current as large as several tens to several hundreds of milli-amperes. + C1 47µF *Q1 2SD µH R1 300 C2 10nF EXT GS SS14 GND V + C3 100µF V *Q1: Sanyo 25D13S-TC V/5A/20W 100mA oad Current Step-Up Converter Analog Integrations Corporation 4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan DS TE: FAX:

2 ORDERING INFORMATI AIC1639-XXCXXX ORDERING INFORMATI EX: CXTR PACKING TYPE TR: TAPE & REE BG: BAG PACKAGE TYPE X: SOT-89 Z: TO-92 PUT VOTAGE 27: 2.7V 30: 3.0V 33: 3.3V 50: 5.0V 2.7V Version, in SOT-89 Package & TR SOT-89 TOP VIEW 1: GND 2: V 3: EXT TO-92 TOP VIEW 1: GND 2: V 3: EXT Packing Type ABSOUATE MAXIMUM RATINGS Supply Voltage (V Pin)..12V EXT pin Voltage.-0.3V to Vout+0.3V EXT pin Current.± 50mA Operating Temperature Range.-40 C to 85 C Storage Temperature Range -65 C to 150 C ead Temperature (Soldering 10 Sec.) 2 C TEST CIRCUIT AIC V V EXT F GND Oscillator Test Circuit 2

3 EECTRICA CHARACTERISTICS (T A =25 C, I O =10mA, Unless otherwise specified) PARAMETER TEST CDITIS SYMBO MIN. TYP. MAX. UNIT V IN =1.8V Output Voltage V IN =1.8V V IN =2.0V V V V IN =3.0V Input Voltage V IN 8 V Start-Up Voltage I =1mA, V IN :0 2V V START V Hold-on Voltage I =1mA, V IN :2 0V V HOD 0.6 V No-oad Input Current I =0mA I IN 18 µa 45 I DD1 50 µa Supply Current 1 EXT at no load, V IN =V x 0.95 Measurement of the IC input current (V Pin) 7 I DD2 7 µa Supply Current 2 EXT at no load, V IN =V Measurement of the IC input current (V Pin) 300 EXT H On-Resistance V EXT =V 0.4V R EXTH Ω 110 EXT On-Resistance V EXT = 0.4V R EXT Ω 3

4 EECTRICA CHARACTERISTICS (Continued) PARAMETER TEST CDITIS SYMBO MIN. TYP. MAX. UNIT Oscillator Duty Cycle Max. Oscillator Freq. V IN =V x 0.95 Measurement of the EXT Pin Waveform V IN =V x 0.95 Measurement of the EXT Pin Waveform DUTY % F OSC KHz Efficiency η % TYPICA PERFORMANCE CHARACTERISTICS Inductor (1) : 33µH (Pin Type) Capacitor (C1) : 47µF (Tantalum Type) Diode (D1) : 1N5819 Schottky Type Transistor (Q1) : 2SD Output Voltage (V) V IN=1.8V Efficiency (%) V IN=1.8V Fig. 1 oad Regulation (=33µH) Fig. 2 Efficiency (=33uH) Output Voltage (V) V IN=1.8V Fig. 3 oad Regulation (=33µH) Efficiency (%) 85 V IN=1.8V Fig. 4 Efficiency (=33µH) 4

5 TYPICA PERFORMANCE CHARACTERISTICS (Continued) Output Voltage (V) Efficiency (%) Fig. 5 oading Regulation (=33µH) Fig. 6 Efficiency (=33µH) Output Voltage (V) V IN=3.0V Fig. 7 oad Regulation (=33µH) Efficiency (%) Fig. 8 Efficiency (=33µH) V IN=3.0V Output Voltage (V) Start up Input Voltage (V) Start up Hold on Hold on Fig. 9 Start-up & Hold-on Voltage (=33µH) Fig. 10 Start-up & Hold-on Voltage (=33µH) 5

6 TYPICA PERFORMANCE CHARACTERISTICS (Continued) Input Voltage (V) Start up Hold on Input Voltage (V) Start up Hold on Fig. 11 Start-up & Hold-on Voltage (=33µH) Fig. 12 Start-up & Hold-on Voltage (=33µH) Start up Start up Input Voltage (V) Hold on Input Voltage (V) Hold on Fig. 13 Start-up & Hold-on Voltage (=33µH) Fig. 14 Start-up & Hold-on Voltage (=33µH) Output Voltage (V) V =5.0V V = 3.3V V = 3.0V V = 2.7V Switching Frequency (khz) V = 5.0V V = 3.3V V = 3.0V V = 2.7V Fig. 15 AIC1639 Output Voltage vs. Temperature Fig. 16 AIC1639 Switching Frequency vs. Temperature 6

7 TYPICA PERFORMANCE CHARACTERISTICS (Continued) Maximum Duty Cycle (%) V = 2.7V V = 3.0V V = 3.3V V = 5.0V Fig. 17 AIC1639 Maximum Duty Cycle vs. Temperature Supply Current IDD1 (µa) V = 5.0V V = 3.3V V = 3.0V V = 2.7V Temperature ( C) Fig. 18 AIC1639 Supply Current vs. Temperature Resistance (O) V = 2.7V V = 3.0V V = 3.3V V = 5.0V Resistance (O) V = 2.7V V = 3.0V V = 3.3V V = 5.0V Temperature ( C) Fig. 19 AIC1639 EXT "" On-Resistance Temperature ( C) Fig. 20 AIC1639 EXT "H" On-Resistance BOCK DIAGRAM V 1.25V REF. 1M - + EXT GND Enable OSC, 100KHz 7

8 PIN DESCRIPTIS PIN 1 : GND - Ground. Must be low impedance; solder directly to ground plane. PIN 2 : V - IC supply pin. Connect V to the regulator output. PIN 3: EXT - Push Pull driver output for external power switch. APPICATI INFORMATI GENERA DESCRIPTI AIC1639 PFM (pulse frequency modulation) controller ICs combine a switch mode regulator, push pull driver (AIC1639), 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 ( 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 turn-on time. Switching frequency depends on load, input voltage, and inductor value, and it can range up to 100KHz. 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. The continuous conduction mode means that the inductor current does not ramp to zero during each cycle. V IN I IN I D I SW EXT + Isw Ico V 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 forces 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. 8

9 V EXT I IN I PK At the boundary between continuous and discontinuous mode, output current (IOB) is determined by I OB = V VIN + V D * 1 V * 2 where V D is the diode drop, IN * T * ( 1 x) I SW X = (R T + RS) R = Switch turn on resistance, R S = Inductor DC resistance I D T DIS V SW Charge Co. Discharge Co. Discontinuous Conduction Mode V EXT I t T = Switch time In the discontinuous mode, the switching frequency (Fsw) is F 2() * (V = V + V * T ) * (I ) * (1 D IN SW IN In the continuous mode, the switching frequency is 1 fsw = T ( V + VD IN) * (V + V D SW x VIN SW * [1+ ( )] 2 V + VD SW 1 V + VD IN * T V + VD SW ) x) I IN I PK where Vsw = switch drop and proportion to output current. I SW I D V SW I Continuous Conduction Mode t INDUCTOR SEECTI To operate as an efficient energy transfer element, the inductor must fulfill three requirement. 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 time. Second, the inductance must also be high enough so maximum current rating of AIC1639 and inductor are not exceed at the other worst case condition of maximum input voltage and time. astly, the inductor must have sufficiently low DC resistance so excessive power is not lost as heat 9

10 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 time, peak current and energy in the inductor build according to I PK VIN R + R = * 1 exp( R + RS VIN x * ( T ) * 1 2 VIN * T (simple lossless equation), where X = (R 1 E = * IPK 2 T + RS) 2 S * T ) Power required from the inductor per cycle must be equal or greater than P f SW = (V + V D IN ) * (I 1 ) * ( 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 I PK V = * I + VD VIN SW V + IN Valley current (Iv) is I V V = V * VD VIN SW IN DE * T SW SW SW * x 2 * T x * I 2 x 1 2 * 1 ) x 2 Table 1 Indicates resistance and height for each coil. Power Inductor Type Inductance ( mh ) Resistance ( Ω ) Rated Current (A) height (mm) Sumida SMT Type CD54 Hold SMT Type PM Hold SMT Type PM Huan Feng PIN Type V m

11 CAPACITOR SEECTI 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 ES. There are low ESR aluminum capacitors for switch mode DC-DC converters which work much better than generalpurpose unit. Tantalum capacitors provide still better performance at more expensive. OS-C 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 SEECTI COMPENT POWER DISSIPATI Operating in discontinuous mode, power loss in the winding resistance of inductor can be approximate equal to 2 T V + V PD = * * * 3 V D ( RS) * ( P) where P =V * I ; R S =Inductor DC R; V D = Diode drop. The power dissipated in a switch loss is PDsw = 2 T * 3 * ( R )* ( I )* ( P ) The power dissipated in rectifier diode is V V PD D = D * ( P ) 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 startup voltage will suffer substantially. 11

12 PHYSICA DIMENSIS SOT-89 (unit: mm) D D1 A C SYMBO MIN MAX A B C H E D D e e1 B E e 1.50 (TYP.) e (TYP.) H SOT-89 MARKING Part No. Marking AU27 AU30 AU33 AU50 TO-92 (unit: mm) A C E SYMBO MIN MAX A C 0.38 (TYP.) D e1 D E e (TYP.)