+ C1. Note: V IN 1.8V, V OUT 7V. High Efficiency Step-Up DC/DC Converter

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1 2-Cell, 500mA, Step-Up DC/DC Converter ❶ FEATURES High Efficiency %. Adjustable Output Voltage with Two Resistors (AI631A) Power-Saving Shutdown Mode (7µA typical). Internal 2A Switch. 120KHz Switching Rate. Adjustable Switch Current Limit. On-Chip Low Battery Detector. ❶ APPLICATIONS Palmtop & Notebook Computers. Pocket Organizers. Cameras. Pagers. Battery Backup Supplies. Portable Instruments. ❶ DESCRIPTION The AI631 is a high efficiency step up DC- DC converter. Only four external components are required to deliver a fixed voltage of 3V, 3.3V, or 5V. The output voltage can be externally set to an arbitrary value below breakdown voltage of the power switch for AI631A. Efficiency beyond 87% can be easily achieved at 0mA load with 2.2V to 3V input voltages. Logic-controlled shutdown mode is provided for power saving. Switch current limit can be programmed with a resistor. The low battery detector can be configured as a linear regulator or a burst mode controller performing an extremely low supply current operation. 120KHz switching rate reduces the inductor size. Inductors of 25µH to 50µH inductance are recommended for most applications. ❶ TYPICAL APPLICATION CIRCUIT V OUT (3.3V) 0µF V IN L 0Ω 50µH Note: V IN 1.8V, V OUT 7V 0µF NORMAL SD R ILIM High Efficiency Step-Up DC/DC Converter SGND AI631 CGND Analog Integrations Corporation 4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC DS Dec 27, 00 TEL: FAX:

2 ❶ ORDERING INFORMATION AI631 XXX PACKAGE TYPE N: PLASTIC DIP S: SMALL OUTLINE TEMPERATURE RANGE C=0 C~70 C OUTPUT VOLTAGE DEFAULT: 3.3V 3: 3.0V 5: 5.0V A: Adjustable ORDER NUMBER AI631CN AI631-3CN CN (PLASTIC DIP) AI631CS AI631-3CS CS (PLASTIC SO) AI631ACN (PLASTIC DIP) AI631ACS (PLASTIC SO) PIN CONFIGURATION TOP VIEW SGND 4 5 CGND TOP VIEW EXT 3 6 GND 4 5 FB ❶ ABSOLUTE MAXIMUM RATINGS Supply Voltage V Operating Temperature Range C ~ 80 C Storage Temperature Range C ~ 150 C ❶ TEST CIRCUIT Refer to Typical Application Circuit. ❶ ELECTRICAL CHARACTERISTICS (V IN =3.0V,, unless otherwise specified.) PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNIT Input Voltage Fig. 4 in Appl. Examples V Output Voltage I =200mA AI631 AI V Switch off Current µa No Load Current AI631/AI µa Shutdown Mode Current 7 15 µa Shutdown Recovery Time V IN =2.5V, I =200mA 0.4 ms 2

3 ❶ ELECTRICAL CHARACTERISTICS (CONTINUED) PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNIT Efficiency I =200mA AI631/AI % Line Regulation I =0mA AI631, V IN =1.8 ~ 3.3V AI631-3, V IN =1.8 ~ 3V, V IN =2.2 ~ 3.3V %V OUT Load Regulation I =~300mA AI631/AI %V OUT Oscillator Frequency KHz Pin Trip Point V FB Threshold Voltage AI631A V ON Resistance AI631/AI Ω ON Resistance V IN =2V 45 Ω Off Leakage 1 µa Input Pin Bias Current na/pin Output Pin Leakage na/pin ❶ TYPICAL PERFORMANCE CHARACTERISTICS Switch Voltage vs. Current AI631/ ON Resistance vs. Temperature AI631/ V (V) 0.5 RDS (Ω) I (A) Temperature ( C) 3

4 ❶ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) 200 No Load Supply Current vs. Input Voltage 2 No Load Supply Current vs. Temperature IS (µa) AI631/ IS (µa) AI631/ V IN (V) Temperature ( C) 8.2 Shutdown Mode Supply Current vs. Input Voltage 9.4 Shutdown Mode Supply Current vs. Temperature V IN=3V IS (µa) IS (µa) (V) Temperature ( C) Frequency (KHz) Oscillator Frequency vs. Input Voltage V IN (V) Oscillator Frequency (KHz) Oscillator Frequency vs. Temperature V IN=3V Temperature ( C) 4

5 ❶ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) Maximum Load Current (ma) Maximum Load Current vs. Switch Current Limit Resistance V IN =2.2V V IN =2.5V AI631/ (5% V OUT Drop) R ILIM (KΩ) V IN =2.0V V IN =1.8V Maximum Load Current (ma) Maximum Load Current vs. Switch Current Limit Resistance V IN =2.0V V IN =2.7V V IN =2.2V V IN =2.5V R ILIM (KΩ) AI631/ (5% V OUT Drop) V IN =1.8V ❶ BLOCK DIAGRAM Current Limit - 0mV - Shutdown 0.617V - A 1.22V OSC SGND CGND 5

6 ❶ PIN DESCRIPTIONS AI631/ AI631-3 / PIN 1: - 1. Connected to pin through a resistor to set the switch peak current. It serves to protect IC and inductor, as well as to improve efficiency and output ripples. However, supply capability of the AI631 is limited by the current limit resistor. (See typical performance characteristics). The pin should be shorted to pin if limiting on switch peak current is not intended. PIN 2: - Input supply. 2. The AI631 goes in shutdown mode and consumes less than µa when pin is pulled to ground. PIN 3: - Drain of the power switch, to be connected to inductor/ diode. PIN 4:SGND - PIN 5:CGND - Ground connected to source of power switch. Ground for control circuits of the IC. It should be separated from SGND to avoid the interference. PIN 6: - Open drain output of the battery low detector, with 45Ω ON resistance at V IN =2V. It is pulled low when the voltage on pin is below 1.22V. PIN 7: - The noninverting input of the battery low detector, of which the inverting input is internally connects to 1.22V voltage reference. PIN 8: - The output voltage feedbacks to the IC through this pin. AI631A PIN 1: - 1. Connected to pin through a resistor to set the switch peak current. It serves to protect IC and inductor, as well as to improve efficiency and output ripples. However, supply capability of the AI631A is limited by the current limit resistor. (See typical performance characteristics). The pin should be shorted to pin if limiting on switch peak current is not intended. 2. The AI631A goes in shutdown mode and consumes less than µa when pin is pulled to ground. PIN 2: - Input supply. PIN 3: - Drain of the power switch, to be connected to inductor/ diode. PIN 4: GND - Ground. PIN 5: FB - Output voltage can either be internally set to 5 volt by grounding FB pin, or be externally set to an arbitrary voltage by applying to FB pin the divider voltage of two divider resistors. voltage is given by the following equation: = 1 R where = Resistor connected between FB pin and pin. R2= Resistor connected between FB pin and ground. =Output voltage to be set. PIN 6: - Open drain output of the battery low detector, with 45Ω ON resistance at V IN =2V. It is pulled low when the voltage on pin is below 1.22V. 6

7 AI631A (continued) PIN 7: - The noninverting input of the battery low detector, of which the inverting input is internally connects to 1.22V voltage reference. PIN 8: - The output voltage feedbacks to the IC through this pin. If output voltage was externally set, the pin can be tied to any low impedance node with voltage between the external power switch threshold and 7V ❶ APPLICATION EXAMPLES V OUT (3V) OSCON 0µF C3 50µH L1 V IN 22Ω 0µF 47µF 27K R2 SGND AI631-3 CGND Efficiency (%) Fig. 1 3V Output Step-Up Converter V IN =1.8V Load Current (ma) V IN =3.3V V IN =3.0V V IN =2.5V V IN =2.2V V IN =2.0V V OUT (5V) OSCON 0µF C3 25µH L1 V IN 22Ω 0µF 47µF 27K R2 SGND CGND Efficiency (%) Fig. 2 5V Output Step-Up Converter V IN =2.2V V IN =2.0V V IN =2.5V Load Current (ma) V IN =5.0V V IN =4.5V V IN =4.0V V IN =3.0V

8 ❶ APPLICATION EXAMPLES (CONTINUED) V OUT (3V) V IN 0Ω 80 V IN =1.6V V IN =1.4V 47µF L1 µf Efficiency (%) V IN =1.0V V IN =1.2V 0µF SGND AI631-3 CGND Load Current (ma) Fig. 3 1-Cell Input 3V Output Step-Up Converter V OUT (5V) V IN 0Ω 80 0µF 47µH L1 µf SGND CGND Efficiency (%) V IN=1V V IN =1.2V V IN =1.6V V IN =1.4V Load Current (ma) Fig. 4 1-Cell Input 5V Output Step-Up Converter 2SB1424 Q1 500µH L1 0µF V IN 0Ω 27K R2 220µF µf SGND CGND 15K R5 RB 12K 20K R4 62K R3 V OUT (5V) 0µF C4 Efficiency (%) V IN =6V Load Current (ma) V IN =5V V IN =4V V IN=3V V IN =7V V IN =8V Fig. 5 4-Cell Input Step-Up / Step-Down Converter 8

9 ❶ APPLICATION EXAMPLES (CONTINUED) V IN V OUT (5V) 0µF 50µH L1 0Ω 47µF SGND CGND * CTL= GND in Burst Mode CTL= in Normal Mode 1N4148 D2 *CTL 1M R2 15nF C4 C3 1µF 1M R3 Q2 2N34 680K R4 Q1 2N34 Total Supply Current (µa) V IN =2.0V V IN =2.5V V IN =1.8V V IN =3V Load Current (µa) Fig. 6 Low Supply Current Burst Mode Step-Up Converter V OUT V IN 50µH L1 0µF 22Ω 47µF 27K R2 OSCON 0µF C3 GND AI631A FB R2 Fig.7 Adjustable Output Voltage Step-Up Converter 9

10 ❶ PHYSICAL DIMENSION 8 LEAD PLASTIC SO (unit: mm) D H E e A C A1 SYMBOL MIN MAX A A B C D E e 1.27(TYP) H L B L 8 LEAD PLASTIC DIP (unit: mm) D SYMBOL MIN MAX A E1 A b E C D A2 E L A1 C E e 2.54 (TYP) b e eb eb.92 L