AIC1620/AIC1621/AIC1622 High Efficiency Synchronous Step-Up DC/DC Converter n DESCRIPTION n FEATURES High Efficiency 93% (V IN=2.4V, VOUT =3.3V, IOUT =200mA). The AIC1620/AIC1621/AIC1622 are high effi- l 20µA Quiescent Supply Current. voltage is as low as 0.8V and operate with an l Power-Saving Shutdown Mode (0.1µA typical). input voltage down to 0.7V. Consuming only l Internal Synchronous Rectifier ( no external diode ) 20µA of quiescent current. These devices offer l Selectable Current Limit for Reduced Ripple ( AIC1622 ). size and cost by eliminating the need for an ex- l Low Noise , Anti-Ringing Feature ( AIC1622 ) ternal Schottky diode and improves overall effi- l On-Chip Low Battery Detector. ciency by minimizing losses. l Low Battery Hysteresis The switching frequency depends on the load l ciency step up DC-DC converter. The start-up a built-in synchronous rectifier that reduces and the input voltage can range up to 500KHz. n APPLICATIONS The peak current of the internal switch is fixed l Palmtop & Notebook Computers. at 0.8A (AIC1620), at 0.45A (AIC1621), or is l PDAs selectable (AIC1622) for design flexibility. Rip- l Wireless Phones ple does not exceed the product of the switch l Pocket Organizers. current limit and the filter capacitor equivalent l Cameras. series resistance (ESR). The AIC1622 also fea- l 1 to 2-Cell Hand-Held Devices tures a circuit that eliminates noise due to inductor ringing. n TYPICAL APPLICATION CIRCUIT VIN ON + 100µF OFF 22µH LX SHDN Low-Battery Detect In LBI AIC1620 AIC1621 AIC1622 REF OUT LBO FB LBO GNDFB Output 3.3V, or Adj. (1.8V to 4.0V) up to 300mA + 220µF Low-Battery Detect Out 0.1µF Analog Integrations Corporation 4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw DS-1620-00 032502 1 AIC1620/AIC1621/AIC1622 n ORDERING INFORMATION AIC1620CX XX AIC1621C X XX AIC1622C X XX PIN CONFIGURATION (MSOP8) PACKING TYPE TR: TAPE & REEL PACKAGING TYPE O: MSOP8 (for AIC1620/1) O: MSOP10 (for AIC1622) TOP VIEW FB 1 8 OUT LBI 2 7 LX 6 GND 5 SHDN LBO 3 AIC1620 AIC1621 REF 4 TOP VIEW (MSOP10) FB 1 Example: AIC1620COTR à In MSO8 Package & Taping & Reel Packing Type 10 OUT LBI 2 LBO 3 9 LX AIC1622 8 GND CLSEL 4 7 BATT REF 5 6 SHDN n ABSOLUTE MAXIMUM RATINGS Supply Voltage (OUT to GND) Switch Voltage (LX to GND) 8.0V VOUT + 0.3V Battery Voltage (Batt to GND) 6.0V SHDN , LBO to GND 6.0V LBI, REF, FB, CLSEL to GND VOUT +0.3V Switch Current (LX) -1.5A to +1.5A Output Current (OUT) -1.5A to +1.5A Operating Temperature Range -40°C ~ +85°C Storage Temperature Range -65°C ~150°C n TEST CIRCUIT Refer to Typical Application Circuit. 2 AIC1620/AIC1621/AIC1622 n ELECTRICAL CHARACTERISTICS (V BATT=2.0V, VOUT=3.3V (FB=VOUT), RL=∝, TA=25°C, unless otherwise specified.) PARAMETER TEST CONDITIONS MIN. Minimum Input Voltage 1.1 RL=3KΩ (Note1) 0.8 Start-Up Voltage Tempco 1.8 FB = VOUT AIC1620 AIC1622 (CLSEL=OUT) Steady State Output Current FB=OUT (Note 2) ( VOUT =3.3V) AIC1621 AIC1622 (CLSEL=GND) Reference Voltage IREF= 0 UNIT V 4.0 V 1.1 V -2 Output Voltage Range Output Voltage MAX. 0.7 Operating Voltage Start-Up Voltage TYP. mV/°C 4.0 3.17 3.3 300 400 3.43 V mA 150 220 1.199 1.23 Reference Voltage Tempco 1.261 0.024 V mV/°C Reference Load Regulation IREF = 0 to 100 µA 10 30 mV Reference Line Regulation VOUT = 1.8V to 4V 5 10 mV/V 1.23 1.261 V FB , LBI Input Threshold Internal switch On-Resistance 1.199 ILX = 100mA Ω 0.3 AIC1620,AIC1622(CLSEL = OUT) 0.6 0.8 1.0 AIC1621,AIC1622(CLSEL = GND) 0.3 0.45 0.6 0.05 1 µA LX Switch Current Limit A LX Leakage Current VLX=0V, 4V; VOUT =4V Operating Current into OUT VFB = 1.4V , VOUT = 3.3V 20 35 µA SHDN = GND 0.1 1 µA VOUT = 3.3V ,ILOAD = 200mA 90 VOUT = 2V ,ILOAD = 1mA 85 (Note 3) Shutdown Current into OUT Efficiency % LX Switch On-Time VFB =1V , VOUT = 3.3V 2 4 7 µS LX Switch Off-Time VFB =1V , VOUT = 3.3V 0.6 0.9 1.3 µS FB Input Current VFB = 1.4V 0.03 50 nA 3 AIC1620/AIC1621/AIC1622 n ELECTRICAL CHARACTERISTICS (Continued) PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNIT 1 50 nA LBI Input Current VLBI = 1.4V CLSEL Input Current AIC1622 , CLSEL = OUT 1.4 3 µA SHDN Input Current V SHDN = 0 or VOUT 0.07 50 nA LBO Low Output Voltage VLBI = 0, ISINK = 1mA 0.2 0.4 µA LBO Off Leakage Current V LBO = 5.5V, VLBI = 5.5V 0.07 1 LBI Hystereisis 50 Damping Switch Resistance AIC1622, VBATT = 2V mV 50 100 Ω 0.2V OUT SHDN Input Voltage V 0.8V OUT 0.2V OUT CLSEL Input Voltage V 0.8V OUT Note 1: Start-up voltage operation is guaranteed without the addition of an external Schottky diode between the input and output. Note 2: Steady-state output current indicates that the device maintains output voltage regulation under load. Note 3: Device is bootstrapped (power to the IC comes from OUT). This correlates directly with the actual battery supply. n TYPICAL PERFORMANCE CHARACTERISTICS 100 160 90 Input Battery Current (µA) 140 Efficiency (%) 80 120 V IN=2.4V 70 100 VIN=1.2V 60 50 40 30 20 80 I_limit=0.8A , VOUT=3.3V 60 40 I_limit=0.45A , V OUT=3.3V 20 10 0 0.01 0.1 1 10 100 1000 0 0.0 VOUT =3.3V CLSEL=OUT (0.8A) 1.0 1.5 2.0 2.5 3.0 Input battery voltage (V) Loading (mA) Fig. 1 0.5 Fig. 2 No-Load Battery Current vs. Input Battery Voltage 4 AIC1620/AIC1621/AIC1622 n TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 1.8 100 1.6 Start-up Voltage (V) Efficiency (%) 90 80 V IN =2.4V 70 V IN =1.2V 60 1.4 1.2 1.0 Without Diode 0.8 0.6 With Diode 0.4 50 0.2 0.1 1 10 100 0.0 0.01 1000 0.1 1 10 100 Loading (mA) Load Current (mA) Fig. 3 VOUT=3.3V CLSEL=GND (0.45A) Fig. 4 Start-up Voltage vs. Load Current 0.10 2.2 0.08 2.0 Shutdown Threshold (V) Shutdown Current (µA) 40 0.01 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 -0.10 1.0 1.5 2.0 Fig. 5 2.5 3.0 3.5 4.0 VOUT (V) Shutdown Current vs. VOUT 0.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Output Voltage (V) Fig. 6 Shutdown Threshold vs. Output Voltage Maximum Output Current (mA) 800 LX pin waveform VOUT=3.3V 700 600 CLSEL=OUT VOUT AC Couple 500 400 300 200 CLSEL=GND 100 Inductor Current VIN =2.4V VOUT =3.3V 0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 Input Voltage (V) Fig. 7 Maximum Output Current vs. Input Voltage Fig. 8 Heavy Load Waveform 5 AIC1620/AIC1621/AIC1622 n TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 9 VIN =2.4V VOUT=3.3V Without Damping Ringing Function Fig. 10 With Damping Ringing Function ∆ IOUT=200mA VOUT AC Couple Fig. 11 Load Transient Response 6 AIC1620/AIC1621/AIC1622 n BLOCK DIAGRAM SHDN CLSEL OUT Minimum Off-Time + Q1 One Shot L 1 47µF Q R C3 220µF R1 BATT 200Ω LX Q2 F/F S Damping Switch Q3 OUT 0.1µF VIN + C1 100µF GND One Shot Maximum On-Time + Mirror FB + + LBO Reference Voltage REF C4 0.1µF LBI n PIN DESCRIPTIONS AIC1620/ AIC1621 PIN 1: FBConnect to OUT for +3.3V output. Use a resistor network to set the output voltage from +1.8V to +4.0V. PIN 2: LBILow-battery comparator input. n I ternally set to trip at +1.23V. PIN 3: LBO- Open-drain low battery comparator output. Output is low when VLBI is <1.23V. LBO is high impedance during shutdown. PIN 4: REF- 1.23V reference voltage. Bypass with a 0.1µF capacitor. PIN 5: SHDN- Shutdown input. High=operating, low=shutdown. PIN 6: GND- Ground PIN 7: LXN-channel and P-channel power MOSFET drain. PIN 8: OUT- Power output. OUT provides bootstrap power to the IC. 7 AIC1620/AIC1621/AIC1622 AIC1622 PIN 1: FB- Connect to OUT for +3.3V output. Use a resistor network to set the output voltage from +1.8V to +4.0V. PIN 2: LBILow-Battery comparator input. Internally set to trip at +1.23V. PIN 3: LBO- Open-drain low battery comparator output. Output is low when VLBI is <1.23V. LBO is high impedance during shutdown. PIN 4: CLSEL- Current-limit selects input. CLSEL= OUT sets the current limit to 0.8A. CLSEL=GND sets the current limit to 0.45A. PIN 5: REF- 1.23V reference voltage. Bypass with a 0.1µF capacitor. PIN 6: SHDN- Shutdown input. High=operating, low=shutdown. PIN 7: BATT- Battery input and damping switch connection. If damping switch is unused, leave BATT unconnected. PIN 8: GND- Ground. PIN 9: LXN-channel and P-channel power MOSFET drain. PIN 10: OUT- Power output. OUT provides bootstrap power to the IC. n APPLICATION INFORMATION Overview The AIC1620/AIC1621/AIC1622 series are high efficiency, step-up DC-DC converters, designed to feature a built-in synchronous rectifier, which reduces size and cost by eliminating the need for an external Schottky diode. The start-up voltage is as low as 0.9V and operate with an input voltage down to 0.7V. Quiescent supply current is only 20µA. In addition, the AIC1622 feature a circuit that eliminates inductor ring to reduce noise. The internal P-MOSFET onresistance is typically 0.3Ω to improve overall efficiency by minimizing AC losses. The current limit of the AIC1620 and AIC1621 are 0.8A and 0.45A respectively. The AIC1622 offers a selectable current limit(0.45A or 0.8A). The lower current limit allows the use of a physically smaller inductor in spacesensitive applications. PFM Control Scheme The key feature of the AIC1620 series is a unique minimum-off-time, current-limited, pulse-frequencymodulation (PFM) control scheme (see BLOCK DIAGRAM) with the ultra-low quiescent current . A constant-peak-current limit in the switching allows the inductor current to vary between this peak limit and some lesser value. The peak current of the internal NMOSFET power switch can be fixed at 0.8A, 0.45A or is selectable. Besides, the ripple voltage dose not exceed the product of the peak current limit and the filter capacitor equivalent series resistance (ESR). The switch frequency depends on the loading condition and input voltage, and can range up to 500KHz. The switching frequency is governed by a pair of oneshots that set a minimum off-time (1µS) and a maximum on-time (4µS). 8 AIC1620/AIC1621/AIC1622 Synchronous Rectification BATT/Damping Switch Using the internal synchronous rectifier eliminates the The AIC1622 is designed with an internal damping need for an external Schottky diode. Therefore, the switch (Fig. 15) to reduce ringing at LX. The damping cost and board space is reduced. During the cycle of switch supply a path to quickly dissipate the energy off-time, the P-MOSFET turns on and shunts the N- stored in inductor and reduces the ringing at LX. MOSFET. turn-on Damping LX ringing dose not reduce VOUT ripple, but resistance of MOSFET, the synchronous rectifier sig- dose reduce EMI. R1=200Ω works well for most ap- nificantly improves efficiency without the addition of plication while reducing efficiency by only 1%. Larger an external component. Thus, the conversion efficien- R1 value provide less damping, but less impact on ef- cy can be as high as 93%. ficiency. In principle, lower value of R1 is needed to Due to the low fully damp LX when the VOUT /VIN ratio is high. Reference Voltage The reference voltage (REF) is nominally 1.23V for Selecting the Output Voltage excellent T.C. performance. In addition, REF pin can VOUT can be simply set to 3.3V by connecting the FB source up to 100µA to external circuit with good load pin to OUT due to internal resistor divider (Fig. 16). In regulation (<10mV). A bypass capacitor of 0.1µF is order to adjust the output voltage, a resistor divider is required for proper operation and good performance connected to VOUT, FB, GND (Fig. 17). Use the following equation to calculate: Shutdown The whole circuit is shutdown when VSHDN is low. During shutdown mode, the current can flow from the R5=R6 [(V OUT / VREF )-1] Where VREF =1.23V and VOUT may range from 1.8V to 4V. battery to the output due to body diode of the PMOSFET. VOUT falls to approximately Vin-0.6V and LX remains high impedance. The capacitance and Low-Battery Detection load at OUT determine the rate at which VOUT decays. The AIC1620 series contain an on-chip comparator Shutdown can be pulled as high as 6V. Regardless of with 50mV internal hysteresis (REF, REF+50mV) for the voltage at OUT. low battery detection. If the voltage at LBI falls below the internal reference voltage. LBO ( an open-drain output) sinks current to GND. Current Limit Select Pin The AIC1622 series allows a selectable inductor current limit of either 0.45A or 0.8A. This allows flexibility in designing for higher current or smaller applications. CLSEL draws 1.4µA when connected to OUT. 9 AIC1620/AIC1621/AIC1622 Component Selection be. A filter capacitor with low ESR is helpful to 1. Inductor Selection the efficiency and steady state output current of An inductor value of 22µH performs well in most AIC1620 series. Therefore HERMEI capacitor LT applications. The AIC1620 series also work with series with 220µF/6.3V is recommended. A inductors in the 10µH to 47µH range. An inductor smaller capacitor (down to 10F with higher ESR) with higher peak inductor current tends a higher is acceptable for light loads or in applications that output voltage ripple (IPEAK×output filter capacitor can tolerate higher output ripple. ESR). The inductor’s DC resistance significantly affects efficiency. We can calculate the maximum output current as follows: VIN VOUT − VIN IOUT ( MAX) = ILIM − t OFF VOUT 2 ×L 3. PCB Layout and Grounding η where IOUT(MAX)=maximum output current in amps Since AIC1622’s switching frequency can range up to 500kHz, it makes AIC1622 become very sensitive. So careful printed circuit layout is m i portant for minimizing ground bounce and noise. IC’s OUT pin should be as clear as possible. And the GND pin should be placed close to the ground VIN=input voltage plane. Keep the IC’s GND pin and the ground L=inductor value in µH leads of the input and output filter capacitors less η=efficiency (typically 0.9) than 0.2in (5mm) apart. In addition, keep all con- tOFF=LX switch’off-time in µS nection to the FB and LX pins as short as possi- ILIM =0.45A or 0.8A ble. In particular, when using external feedback resistors, locate them as close to the FB as pos- 2. Capacitor Selection sible. To maximize output power and efficiency The output voltage ripple relates with the peak in- and minimize output ripple voltage, use a ground ductor current and the output capacitor ESR. Be- plane and solder the IC’s GND directly to the sides output ripple voltage, the output ripple cur- ground plane. Following are the recommended rent also needs to be concerned. The smaller the layout diagrams. capacitor ESR is, the higher the ripple current will Figure 12. Top layer Figure 13. Bottom layer Figure 14. Placement 10 AIC1620/AIC1621/AIC1622 n APPLICATION EXAMPLES VIN VOUT Q1 R1 200Ω OUT DAMPING SWITCH Q3 BATT R1 200Ω L 22µH VIN LX BATT (AIC1622) R3 LBI C1 100µF OUT CLSEL (AIC1622) VOUT C2 0.1µF C3 220µF SHDN LX R4 L1 Q2 R2 100KΩ REF 22µ H 0.1µ F LBO C4 GND AIC1622 FB LOW BATTERY OUTPUT AIC1620 AIC1621 AIC1622 GND Fig. 15. Simplified Damping Switch Diagram Fig. 16 VOUT = 3.3V Application Circuit. VIN R1 200Ω L 22µH LX BATT (AIC1622) R3 LBI VOUT OUT CLSEL (AIC1622) C2 0.1µF SHDN R4 0.1µF C4 C1 100µF 100KΩ R2 REF C3 220µF R5 LBO GND FB AIC1620 AIC1621 AIC1622 LOW BATTERY OUTPUT R6 Fig. 17 An Adjustable Output Application Circuit 11 AIC1620/AIC1621/AIC1622 n PHYSICAL DIMENSION l 8 LEAD MSOP (unit: mm) D E E1 e A2 SYMBOL MIN MAX A1 -- 0.20 A2 0.76 0.97 b 0.28 0.38 C 0.13 0.23 D 2.90 3.10 E 4.80 5.00 E1 2.90 3.10 e L 0.40 0.66 SYMBOL MIN MAX A1 -- 0.20 A2 0.76 0.97 b 0.15 0.30 C 0.13 0.23 D 2.90 3.10 E 4.80 5.00 E1 2.90 3.10 A1 C 0.65 b 10 LEAD MSOP (unit: mm) D E E1 e A2 e C L 0.50 0.40 0.66 A1 l L b L 12