AIC1880 Low Noise, Step-Up PWM DC/DC Converter FEATURES DESCRIPTION 90% High Efficiency 1.6A, 0.3Ω, 12V Internal Power MOSFET 640kHz/1.2MHz Pin-Selectable Operation Frequency 2.6V to 5.5V Input Range Low Shutdown Current: 0.1µA Programmable Soft-Start External Compensation Network Adjustable Output from VIN to 11V Thin 8-Pin MSOP Package The AIC1880 is a step-up DC/DC converter with a 1.6A, 0.3Ω internal power switch. A soft-start programmed with an external capacitor sets the input current ramp rate. Pin-selectable high switching frequency (640kHz or 1.2MHz) allows easy filtering and low noises. An external compensation pin gives users flexibility in setting frequency compensation, which makes it feasible to use the small, low ESR ceramic output capacitors. The AIC1880 converts input ranging 2.6V to 5.5V into output voltage up to 11V. The device is available in a low profile 8-lead MSOP package. APPLICATIONS TFT Bias Supplies Handheld Devices PCMCIA Cards Portable Equipment TYPICAL APPLICATION CIRCUIT 3.3V L 6 Cin 10uF 1.2MHz ON 640kHz 7 OFF 3 1 Ccomp2 20pF Analog Integrations Corporation U1 6.8uH VIN D LX FREQ GND SHDN FB COMP SS Rcomp 33k AIC1880 10V 5 4 SS24 2 Cout 10uF R1 1.6M 8 Css 0.022uF R2 220k Ccomp 1200pF Si-Soft Research Center DS-1880P-02 042507 3A1, No.1, Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan, R.O.C. TEL: 886-3-5772500, FAX: 886-3-5772510 www.analog.com.tw 1 AIC1880 ORDERING INFORMATION AIC1880PX XX PIN CONFIGURATION PACKING TYPE TR: TAPE & REEL TB: TUBE MSOP-8 TOP VIEW COMP 1 PACKAGING TYPE O: MSOP-8 FB 2 SHDN 3 P: LEAD FREE COMMERCIAL GND 4 8 SS 7 FREQ 6 VIN 5 LX Example: AIC1880POTR In MSOP-8 Package & Taping & Reel Packing Type ABSOLUTE MAXIMUM RATINGS VIN, FB, SHDN , COMP, FREQ, SS to GND -0.3 V to 5.5V LX to GND -0.3 V to 12V Operating Ambient Temperature Range TA -20°C to 85°C Operating Maximum Junction Temperature TJ Storage Temperature Range 125°C -65°C to 150°C 260°C Lead Temperature (Soldering 10 Sec.) Thermal Resistance Junction to Case MSOP-8 75°C/W Thermal Resistance Junction to Ambient MSOP-8 180°C/W (Assume no Ambient Airflow, no Heatsink) Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 2 AIC1880 ELECTRICAL CHARACTERISTICS (TA=25°C, VIN= SHDN =3V, FREQ=GND, unless otherwise specified) (Note 1) PARAMETER TEST CONDITION Input Voltage Range Under Voltage Lock Out Quiescent Current SYMBOL MIN TYP MAX UNIT VIN 2.6 2.20 5.5 2.50 V 2.35 UVLO V VFB=1.3V, not switching IIN 0.18 0.35 mA VFB=1V, switching IIN 2 5 mA SHDN =GND IIN 0.1 1 µA Shutdown Current SOFT-START ISS 1.5 4 7 µA FREQ=GND FOSC 540 640 740 kHz FREQ=VIN FOSC 1000 1220 1500 kHz FREQ=GND DC 85 % FREQ=VIN DC 85 % FREQ=GND DC 16 % FREQ=VIN DC 30 % Level to produce VCOMP=1.24V VFB VFB=1.24V IFB Soft-start current SWITCHING REGULATOR OSCILLATOR Frequency Maximum Duty Cycle Minimum Duty Cycle ERROR AMPLIFIER Feedback Voltage FB Input Bias Current FB Voltage Line Regulation Transconductance 1.222 Level to produce VCOMP=1.24V 2.6V < VIN < 5.5V ΔI=5µA 1.24 0 1.258 40 V nA 0.05 0.3 %/V GM 210 µmhos ILIM 1.6 A N-CHANNEL SWITCH Current Limit Internal Switch On-Resistance ILX=1.2A RON 0.3 0.5 Ω Leakage Current VLX=12V ILXOFF 0.01 20 µA 0.3VIN V CONTROL INPUTS Input Low Voltage Input High Voltage Hysteresis SHDN , FREQ VIN=2.6V to 5.5V SHDN , FREQ VIN=2.6V to 5.5V VIL VIH 0.7VIN V V 0.1 VIN SHDN , FREQ FREQ Pull-Down Current IFREQ SHDN Input Current I SHDN 1.8 5 9 µA 0.1 1 µA 3 AIC1880 Note 1: Specifications are production tested at TA=25°C. Specifications over the -20°C to 85°C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC). TYPICAL PERFORMANCE CHARACTERISTICS 95 95 fOSC = 1.2MHz L = 3.3µH 90 85 80 fOSC = 640kHz L = 6.8µH 75 EFFICIENCY (%) EFFICIENCY (%) 85 70 65 60 80 75 fOSC = 1.2MHz L = 6.8µH 70 65 60 VIN = 3.3V VOUT = 5V 55 50 fOSC = 640kHz L = 10µH 90 1 10 100 VIN = 3.3V VOUT = 10V 55 50 1000 1 10 100 1000 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) Fig. 1 Efficiency at VIN=3.3V, VOUT=5V Fig. 2 Efficiency at VIN=3.3V, VOUT=10V ) 95 fOSC = 640kHz L = 10µH 90 EFFICIENCY (%) 85 fOSC = 1.2MHz L = 6.8µH 80 75 70 65 60 VIN = 5V VOUT = 10V 55 50 1 10 100 OUTPUT CURRENT (mA) Fig. 3 Efficiency at VIN=5V, VOUT=10V 1000 NO-LOAD SUPPLY CURRENT (mA) 0.9 0.8 0.7 0.6 fOSC = 640kHz 0.5 0.4 0.3 fOSC = 1.2MHz 0.2 0.1 0.0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) Fig. 4 No-Load supply current 4 AIC1880 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 10.60 1600 OUTPUT VOLTAGE (V) 10.50 o TA = +85 C 10.45 10.40 10.35 10.30 o TA = +25 C 10.25 10.20 10.15 o TA = -20 C 10.10 1400 1200 V OUT = 5V 1000 800 V OUT = 10V 600 400 200 10.05 10.00 MAXIMUM CURRENT (mA) 10.55 0 20 40 60 80 100 120 140 160 180 200 220 240 260 f OSC = 640kHz 0 3.0 3.2 3.4 3.6 Fig. 5 Load regulation 3.8 4.0 4.2 4.4 4.6 4.8 5.0 INPUT VOLTAGE (V) OUTPUT CURRENT (mA) Fig. 6 Maximum output current vs. Input voltage ∆IOUT ∆IOUT fOSC=640kHz L=10µH COUT=32µF RCOMP = 33kΩ CCOMP = 1500pF CCOMP2 = 20pF VOUT AC Couple Fig. 7 Load-transient response at VIN=3.3V, VOUT=10V VOUT AC Couple Fig. 8 Load-transient response at VIN=3.3V, VOUT=5V SHDN SHDN VOUT fOSC=640kHz L=6.8µH COUT=44µF RCOMP = 62kΩ CCOMP = 820pF CCOMP2 = 10pF VIN=3.3V VOUT=10V fOSC=640kHz IOUT=10mA COUT=32µF IL Fig. 9 Startup waveform without soft-start VOUT VIN=3.3V VOUT=10V fOSC=640kHz IOUT=10mA COUT=32µF CSS=4.7nF IL Fig. 10 Startup waveform with soft-start 5 AIC1880 BLOCK DIAGRAM SHDN SHUTDOWN CONTROL VIN SHUTDOWN UNDER VOLTAGE LOCK OUT UVLO SOFTSTART SS COMP ERROR AMPLIFIER FB ERROR COMPARATOR 1.24V CLOCK LX CONTROL AND DRIVER LOGIC 1 N GND FREQ OSCILLATOR CURRENT SENSE RSENSE SLOPE COMPENSATION PIN DESCRIPTIONS PIN 1: COMP - Compensation Pin for Error Amplifier. PIN 2: FB - Feedback Pin with a typical reference voltage of 1.24V. PIN 3: SHDN - Shutdown Control Pin. The Device will turn off when SHDN is Low. PIN 4:GND - Ground. PIN 5: LX - Switch Pin. PIN 6: VIN - Power Supply Pin. PIN 7: FREQ - Frequency Select Pin. Oscillator frequency is 640kHz when FREQ connects to GND, and 1.2MHz when FREQ connects to VIN. PIN 8: SS - Soft-Start Control Pin. Connect a soft-start capacitor to this pin. A 4µA constant current charges the soft-start capacitor. Leave open for no soft-start. 6 AIC1880 COMPONENT SELECTION VIN (V) VOUT (V) fOSC (Hz) 3.3 10 640k 3.3 10 1.2M 3.3 5 640k 3.3 5 1.2M 5.0 10 640k 5.0 10 1.2M L (µH) COUT (µF) 10 (Taiyo Yuden NP06D B100M) 6.8 (Taiyo Yuden NP06D B6R8M) 10 (Taiyo Yuden NP06D B100M) 4.7 (Taiyo Yuden NP06D B4R7M) 10 (Taiyo Yuden NP06D B100M) 6.8 (Taiyo Yuden NP06D B6R8M) 10 ceramic (Taiyo Yuden EMK325BJ106MN-B) 10 ceramic (Taiyo Yuden EMK325BJ106MN-B) 10¯2 ceramic (Taiyo Yuden EMK325BJ106MN-B) 10¯2 ceramic (Taiyo Yuden EMK325BJ106MN-B) 10¯2 ceramic (Taiyo Yuden EMK325BJ106MN-B) 10¯2 ceramic (Taiyo Yuden EMK325BJ106MN-B) RCOMP (kΩ) CCOMP (pF) CCOMP2 (pF) TYPICAL IOUT (MAX) (mA) 39 820 20 250 33 1200 20 250 30 820 10 700 36 1000 20 700 30 1200 20 500 22 1500 56 500 APPLICATION INFORMATION Operation switching frequency is 1.2MHz, as FREQ pin is con- The AIC1880 is a fixed-frequency and high efficiency nected to VIN. For 640kHz operation, an internal step-up DC/DC converter with current-mode PWM pull-low of FREQ pin allows the FREQ pin uncon- control architecture. By selecting appropriate circuit nected. components, it can achieve fast transient response. Current Limitation The AIC1880 can regulate its output voltage through a Current limitation function of AIC1880 will be activated feedback control circuit, which is composed of an error when the peak value of switch current reaches 1.6A amplifier; two comparators and several control signal (typ.). While the current limitation function is activated, generators. By comparing the voltage at FB pin to the the duty cycle will be reduced to limit the output power reference voltage of 1.24, the error amplifier varies the to protect the internal power switch. voltage at COMP pin. The voltage at COMP pin is Soft-Start compared with the summing signal of current sensing The AIC1880 provides the soft-start function. When signal and slope compensation signal to determine the SHDN pin is connected to VIN, an internal current duty cycle of internal power switch. In order to prevent source of 4µA (typ.) charges an external soft-start ca- overcharging the output capacitor and achieve better pacitor. During the soft-start period, the voltage at SS efficiency, AIC1880 will enter pulse-skipping mode pin will decide the allowable peak value of switch cur- (PSM) operation while working at light load conditions. rent. The peak value of switch current is 0A, when the Frequency Selection voltage at SS pin is 0V. In addition, it is in full current The AIC1880’s switching frequency can be selected to limitation when the voltage at SS pin is higher than be either 640kHz or 1.2MHz. The switching frequency 1.0V. The soft-start time can be calculated in accor- is 640kHz, while FREQ pin is connected to GND. The dance with the following equation. 7 AIC1880 t SS = C SS × ciency. The forward drop voltage of a Schottky diode 1 .0 V 4µA will result in the conduction losses in the diode, and the The soft-start capacitor is discharged to GND when the diode capacitance (CT or CD) will cause the switching SHDN pin is connected to GND. losses. Therefore, it is necessary to consider both for- Shutdown ward voltage drop and diode capacitance for diode se- By connecting the SHDN pin to GND, the AIC1880 lection. In addition, the rating of selected Schottky di- can be shut down to reduce the supply current to ode should be able to handle the output voltage and 0.1µA (typ.). At this operation mode, the output voltage the maximum peak diode current. of step-up converter is approximately equal to (VIN–VD). Input Capacitor VD is the forward drop voltage of catch diode. To prevent the large input voltage ripple resulted from Components Selection high frequency switching, the use of low ESR ceramic Inductor capacitor is recommended. A 10µF ceramic capacitor The inductor selection depends on the switching fre- is sufficient for most AIC1880 applications. quency and current ripple of inductor. Output Capacitor L≥ VIN fOSC ⋅ ∆IL ⎛ V ⎞ ⎜⎜1 − IN ⎟⎟ VOUT ⎠ ⎝ The selection of output capacitor depends on the required output voltage ripple. The output voltage ripple The AIC1880’s switching frequency can be selected to be either 640kHz or 1.2MHz. A higher switching frequency allows the use of a smaller inductance. How- can be expressed as: ∆VOUT = IOUT fOSC ⋅ COUT ⎛ V ⎞ ⎜⎜1 − IN ⎟⎟ + ESR ⋅ ∆IL VOUT ⎠ ⎝ ever, higher switching frequency can cause more For lower output voltage ripple, the use of low ESR switching losses, resulting in lower efficiency. By set- ceramic capacitor is recommended. The tantalum ca- ting the switching frequency and an acceptable current pacitor can also be used well, but its ERS is larger than ripple of inductor, a suitable inductance can be ob- that of ceramic capacitor. tained from above equation. Soft-Start Capacitor In addition, it is important to ensure the inductor satu- The soft-start of AIC1880 begins from VSS=0V and ration current exceeds the peak value of inductor cur- ends while VSS reaches 1.0V. During the soft-start pe- rent in application to prevent core saturation. The peak riod, an internal current source of 4µA (typ.) charges value of inductor current can be calculated according the soft-start capacitor. Hence, the soft-start capacitor to the following equation. should be large enough to ensure that the output volt- IPEAK = IIN(max ) + = ⎛ VIN V ⎞ ⎜⎜1 − IN ⎟⎟ 2 × fOSC ⋅ L ⎝ VOUT ⎠ IOUT(MAX ) ⋅ VOUT η ⋅ VIN + ⎛ VIN V ⎜⎜1 − IN 2 × fOSC ⋅ L ⎝ VOUT age has reached the regulation value before the soft-start function has finished. ⎞ ⎟⎟ ⎠ Output Voltage Programming By connecting a resistive divider R1 and R2, the output Diode voltage of AIC1880 step-up converter can be set. VOUT A Schottky diode with low forward drop voltage and can be calculated as: fast reverse recovery is the ideal choice for better effi- 8 AIC1880 ⎛ R ⎞ VOUT = 1.24 × ⎜⎜1 + 1 ⎟⎟ ⎝ R2 ⎠ formance, it is necessary to adjust the component val- The resistive divider should sit as close to FB pin as Layout Consideration possible. In order to ensure a proper operation of AIC1880, the Loop Compensation following points should be managed comprehensively. In order to avoid the poor output voltage ripple and low 1. The input capacitor and VIN should be placed as efficiency caused by instability, AIC1880 requires a close as possible to each other to reduce the input proper external compensation network to compensate ripple voltage. ues of external compensation network. its feedback loop. In this external compensation net- 2. The output loop, which is consisted of the inductor, work, RCOMP is used to set the high-frequency integra- the internal power switch, the Schottky diode and tor gain for fast transient response. While RCOMP is de- the output capacitor, should be kept as small as cided, CCOMP is chosen to set the integrator zero to possible. maintain the loop stability. CCOMP2 is used to cancel the zero caused by the output capacitor and its ESR. While using the ceramic capacitor as the output capacitor, CCOMP2 can be omitted due to the small ESR. R COMP ≅ 10 × CCOMP ≅ COUT VOUT (kΩ ) × L VIN RL ⋅ COUT (F) 10 × R COMP C COMP 2 ≅ ESR × C OUT (F) R COMP 3. The routes with large current should be kept short and wide. 4. Logically the large current on the converter should flow at the same direction. 5. The FB pin should be connected to the feedback resistors directly and the route should be away from the noise sources. 6. The soft-start capacitor should be connected to the SS pin and GND pin directly. For each components of external compensation network, the above equations provide the approximate calculations. In order to obtain better transient per- 9 AIC1880 APPLICATION EXAMPLES D4 BAT54S C10 0.1uF D3 BAT54S Vout2 28V/10mA C8 C12 0.1uF 0.1uF C11 1uF Vout3 -9V/10mA C13 1uF D2 BAT54S C9 0.1uF L1 Vin 3.3V 6 Cin 10uF 7 6.8uH U1 VIN LX FREQ GND 3 SHDN FB 1 COMP SS 4 SS12 2 Cout1 10uF Vout1 10V/200m R1 1.6M 8 Css 0.047uF AIC1880 Rcomp 36k Ccomp2 20pF D1 5 R2 220k Ccomp 1000pF Fig. 11 TFT LCD Bias Supply at VIN=3.3V D4 BAT54S C10 0.1uF D3 BAT54S C8 C12 0.1uF 0.1uF Vout3 C13 1uF D2 BAT54S -9V/10mA Vout2 28V/10mA C11 1uF C9 0.1uF L1 Vin 5.0V Cin 10uF 6 7 3 1 Ccomp2 56pF U1 6.8uH VIN D1 LX FREQ GND SHDN FB COMP Rcomp 22k SS AIC1880 5 4 SS12 2 Cout1 10uF 8 Css 0.047uF Vout1 10V/200mA R1 1.6M R2 220k Ccomp 1500pF Fig. 12 TFT LCD Bias Supply at VIN=5.0V 10 AIC1880 PHYSICAL DIMENSIONS (unit: mm) MSOP-8 D A A SEE VIEW B A2 e MSOP-8 MILLIMETERS MIN. MAX. A E E1 S Y M B O L 1.10 A1 0.05 0.15 A2 0.75 0.95 b 0.25 0.40 c 0.13 0.23 D 2.90 3.10 A E E1 4.90 BSC A1 e L q b 3.10 2.90 0.65 BSC 0.40 0.70 0° 6° 0.25 c WITH PLATING SECTION A-A GAUGE PLANE SEATING PLANE θ L VIEW B BASE METAL Note: 1. Refer to JEDEC MO-187AA. 2. Dimension "D" does not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 6 mil per side . 3. Dimension "E1" does not include inter-lead flash or protrusions. 4. Controlling dimension is millimeter, converted inch dimensions are not necessarily exact. Note: Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AIC product, nor for any infringement of patents or other rights of third parties that may result from its use. We reserve the right to change the circuitry and specifications without notice. Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 11