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| AIC1653 Micropower Inverting DC/DC Converter in SOT-23-5 FEATURES Low Quiescent Current: 15A in Active Mode <1A in Shutdown Mode Operates with VIN as Low as 1.8V Uses Small Surface Mount Components High Output Voltage: Up to -28V Low profile 5-Lead SOT-23-5 Package DESCRIPTION The AIC1653 is a micropower inverting DC/DC converter in 5-lead SOT-23 package. It is designed for power systems with a 100mA current limit and an input voltage ranging from 1.8V to 10V. Besides, AIC1653 features a quiescent current of only 15A at no load, which further reduces to 0.5A when shutdown. The schemes of current limited and fixed off-time control conserve operating current, resulting in high efficiency over a broad range of load current. In addition, the 30V switch of AIC1653 allows high voltage outputs up to -28V, which is easily generated without the use of costly transformers. The AIC1653's low off-time of 400ns permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications. APPLICATIONS LCD Bias Hand-Held Computers Battery Backup Digital Still Cameras TYPICAL APPLICATION CIRCUIT VIN 2.5V~5V C1 4.7F 5 4 2 L1 22H VIN SW 1 C3 0.22F L2 22H D1 RB521S-30 R1 150k VOUT -6V/14mA C2 4.7F SHDN 3 GND NFB AIC1653 R2 39K L1,L2: TOKO D312F 22H D1: Rohm RB521S-30 C1,C2,C3: TAIYO YUDEN Ceramic capacitors 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-1653-02 122203 1 AIC1653 ORDERING INFORMATION AIC1653CXXX PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE V: SOT-23-5 Example: AIC1653CVTR in SOT-23-5 Package & Tape & Reel Packing Type PIN CONFIGURATION SOT-23-5 (CV) FRONT VIEW 1: SW 2: GND 3: NFB 4. SHDN 5: VIN 5 4 1 2 3 SOT-23-5 Marking Part No. AIC1653 Marking 1653 ABSOLUTE MAXIMUM RATINGS VIN, SHDN Voltage SW Voltage NFB Voltage Junction Temperature Operating Temperature Range (Note 2) Storage Temperature Range Lead Temperature (Soldering, 10 sec) (Note 1) 10V 30V -3V 125C -40C to 85C -65C to 150C 300C TEST CIRCUIT Refer to Typical Application Circuit. 2 AIC1653 ELECTRICAL CHARACTERISTICS otherwise specified) PARAMETER Minimum Input Voltage Quiescent Current FB Comparator Trip Point FB Comparator Hysteresis Output Voltage Line Regulation (Note 3) FB Pin Bias Current (Note 4) Switch Off Time Inter Switch On-Resistance Switch Current Limit SHDN Input Voltage High SHDN Input Voltage Low (TA = 25C, VIN = 3.6V, V SHDN = 3.6V unless MIN. TYP. 15 -1.205 -1.23 10 MAX. 1.8 20 1 -1.255 UNIT V A V mV %/V 2.7 A nS nS 1.4 125 0.25 mA V V A 0.01 5 TEST CONDITIONS Not Switching VSHDN = 0V Refer to Fig.7 VNFB = -1.23V NFB-1V NFB-0.6V 0.6 75 0.9 Switch Off, VSW = 5V 1.3 0.05 2 400 800 1 100 Switch Leakage Current Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Output voltage line regulation is guaranteed by design, characterization and correlation with statistical quality controls, not production tested. Note 4: Bias current flows out of the NFB pin. 3 AIC1653 TYPICAL PERFORMANCE CHARACTERISTICS 80 75 70 -1.25 5 FB Comparator Trip Point (V) VIN=3.6V 4 -1.24 Efficiency (%) VIN=2.7V 65 Voltage 3 -1.23 60 55 50 45 2 VIN =4.2V Current 2 -1.22 -1.21 1 4 6 8 10 12 14 16 -1.20 -40 -20 0 20 40 60 80 0 100 Load Current (mA) Fig. 1 Load Current vs. Efficiency (Refer to typical application circuit) 1.5 Temperature (C) Fig. 2 FB Comparator Trip Point and Pin Bias Current vs. Temperature 140 VIN=2.5V Switch Current Limit (mA) 120 100 80 60 40 20 0 -40 Switch ON-Resistance () VIN =3.6V 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 -40 VIN=3.6V, ISWITCH=50mA VIN=4.2V VIN =8.5V VIN =10V -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 Temperature (C) Fig. 3 Switch Current Limit vs. Temperature Temperature (C) Fig. 4 Switch ON-Resistance vs. Temperature Bias Current (A) 4 AIC1653 TYPICAL PERFORMANCE CHARACTERISTICS 850 800 -40 -20 0 (Continued) 20 40 60 80 100 Temperature (C) 24 VIN=3.6V Supply Current (uA) Phase I Switch Off Time (ns) 750 700 650 600 550 500 450 400 -40 -20 0 22 20 18 16 14 12 60 80 100 10 2 4 VIN=1.8V to 12V, Temperature = 20C Temperature=-40C to 100C, VIN =3.6V Phase II 20 40 6 8 10 12 Temperature (C) Fig. 5 Switch Off Time vs. Temperature 7.0 6.8 6.6 Supply Voltage (V) Fig. 6 Quiescent Current vs. Temperature and Voltage Output Voltage (V) 6.4 6.2 6.0 5.8 5.6 5.4 5.2 5.0 2 3 4 5 6 7 8 9 10 VOUT = - 6.0V, IOUT=2mA Input Voltage (V) Fig. 7 Line Regulation 5 AIC1653 BLOCK DIAGRAM VIN SW + R1 R2 + Q1 Q2 R3 + R4 NFB -+ A3 MODE Control SHDN GND A1 400nS/ 800nS One-Shot Bandgap A2 100mV Current Limit Logic Drive -0.6V Fig. 8 Block diagram of AIC1653 PIN DESCRIPTIONS PIN 1: SW - Switch Pin. This is the open drain of the internal N-MOSFET power switch. Minimize the metal trace area connected to this pin to minimize EMI. PIN 2: GND PIN 3: FB - Ground. Tie this pin directly to the local ground plane. - Set the output voltage by values of R1 and R2 (see typical application circuit): PIN 5: VIN R1 = VOUT - 1.23 1.23 + 2 x 10 -6 R2 PIN 4: SHDN - Shutdown Pin. Tie this pin to 0.9V or higher to enable the device. Tie below 0.25V to turn off the device. - Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. 6 AIC1653 APPLICATION INFORMATIONS Principle of Operation AIC1653 uses a constant off-time control scheme, which is represented in Fig. 8, to provide high efficiency over a range of output current. Q1 and Q2 along with R3 and R4 form a bandgap reference used to regulate the output voltage. When the voltage at NFB pin is slightly below -1.23V, comparator A1 disables most of the internal circuitry. Output current is then provided by output capacitor, which slowly discharges until the voltage at the NFB pin goes above the hysteresis point of A1. A1 then enables the internal circuitry to turn power switch NMOS on, and the current in inductor begins ramping up. Once the switch current reaches 100mA, comparator A2 resets one-shot, which turns NMOS off for 400ns. In the meantime, the inductor continues to deliver current to the output. When NMOS turns back on, the inductor current ramps up. And A2 resets one-shot again when switch current gets to 100mA. This switching action continues until the output voltage is charged up with NFB pin reaching -1.23V. Then A1 turns the internal circuitry off and the cycle repeats. The AIC1653 contains additional circuitry to provide current-limit protection for start-up as well as short-circuit protection. When FB pin voltage is higher than -0.6V, switch off-time is increased to 800nS. This reduces the average inductor current and helps minimize the power dissipation in AIC1653 power switch, and in the external inductor and diode. For a converter (typical application circuit) Be aware that, based on formula (1), high output voltage can raise inductance, which may cause an increase of inductor size. Component Selection Inductor Selection - Inverting Regulator The following formula calculates the appropriate inductor value for an inverting regulator. This value provides a good tradeoff in inductor size and system performance. In any applications, the closest value to the one from the formula needs to be applied to the inductors (both inductors should have the same value). A use of an inductor value up to 22H can induce a slight increase of output current, but any value beyond that will result in high output ripple voltage with no further output current increase. The size of inductor can be reduced by using a value under 22H. The formula is shown as below: V OUT + VD L = 2 x t OFF I LIM (1) where VD=0.4V (Schottky diode forward voltage), ILIM=100mA, and tOFF=400nS. converting from 3.6V to -6V, a 51.2H inductor is calculated from the above equation. However, a 22H inductor is recommended instead to prevent the loss of output current. 7 AIC1653 Inductor Selection - Inverting Charge Pump Regulator This topology, inverting charge pump regulator, is recommended when internal power switch voltage is over its maximum rating. As the inverting regulator application above, its internal power switch voltage is 9.6V (the sum of the absolute value of 3.6V input and -6V output), which is fine as it is under the maximum rating, 30V. However, any applications of internal power switch voltage exceeding the maximum rating, topology of inverting charge pump regulator is recommended for their system. For example, a 12V to -30V converter will generate 42V internal power switch voltage, which exceeds its maximum rating 30V. For such a system, an inverting charge pump regulator is the recommended topology. Multilayer ceramic capacitors are the best choice as they have a very low ESR and are available in low-profile packages. Due to the advantage of small size, it makes multilayer ceramic capacitors and AIC1653's SOT-23 packages good companions for size-concerning applications. Solid tantalum capacitors are another alternative for output capacitors, but they take more board area and have larger ESR than ceramics. Input Capacitors Ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to AIC1653. A 4.7F input capacitor is sufficient for most applications. Be aware that, sufficient voltage rating is required for capacitor selection. Diode Selection Appropriate inductor value for an inverting charge pump regulator can be calculated by formula (2). For designs with varying VIN value such as battery-powered applications, minimum VIN value is used in formula (2). L= VOUT - VIN(MIN) + VD t OFF ILIM For most AIC1653 applications, Rohm RB521S-30 surface mount Schottky diode (200mA, 30V) providing the advantage of low forward voltage and fast switching speed is an ideal choice. Note that, generally, rating of handling minimum current at 1A is required for AIC1653 applications. Reducing Output Ripple Voltage (2) Capacitor Selection Output Capacitors Low ESR (Equivalent Series Resistance) capacitors should be used at output terminal to minimize the output ripple voltage. Using low ESR capacitors will help reduce the output ripple voltage. In addition, proper selection of the inductor and the output capacitor plays an important role in output ripple voltage reduction. The AIC1653 provides energy to the output in 8 AIC1653 bursts by ramping up the inductor current, which is then delivered to load. If either inductor value over 22H or capacitor value under 4.7F is used, output ripple voltage will increase because the capacitor will be slightly overcharged in each burst cycle. Two methods of helping reduce output ripple voltage are recommended. One is to increase the output capacitor value. Adding a 100pF feedforward capacitor that is parallel with R1 (see Fig.13) is the other. And the addition of the small capacitor will greatly reduce output ripple voltage. Output Voltage Programming A resistive divider, as in formula (3), sets the output voltage. R1 + R1 x 2 x 10 - 6 VOUT = - 1.23V 1 + R2 A capacitor at 100pF in parallel to the upper feedback resistor is required for a stable feedback. PCB Layout Proper PCB layout and component placement may enhance the performance of AIC1653 application circuit. For a better efficiency, major loop from input terminal to output terminal should be as short as possible. In addition, in a case of a large current loop, the track width of each component in the loop should maintain as wide as possible. In order to get rid of noise interference, separation of Schottky diode ground and output terminal ground into two independent parts is required. Recommended layout diagrams and component placement are shown as Fig. 9 to Fig. 12. ( ) (3) Fig. 9 Top Layer Fig. 10 Bottom Layer 9 AIC1653 Fig. 11 Top Placement Fig. 12 Bottom Placement APPLICATION EXAMPLES VIN 3V~5V C1 4.7F 5 4 2 L1 22H VIN SW 1 C3 0.22F L2 22H D1 RB521S-30 R1 150k C4 100pF VOUT -6V/14mA C2 4.7F SHDN 3 GND NFB AIC1653 R2 39k L1,L2: TOKO D312F 22H D1: Rohm RB521S-30 C1,C2,C3: TAIYO YUDEN Ceramic capacitors Fig. 13 OLED Application for Single Li-Ion Input L1 22H 5 4 2 VIN SW 1 C3 0.22F D1 BAT54S R1 150k C4 100pF VOUT -6V/14mA C2 4.7F VIN 3V~5V C1 4.7F SHDN 3 GND NFB AIC1653 R2 39k L1: TOKO D312F 22H D1: CHENMKO BAT54S C1,C2,C3: TAIYO YUDEN Ceramic capacitors Fig. 14 Inverting Charge Pump Application 10 AIC1653 PHYSICAL DIMENSIONS (unit: mm) SOT-23-5 (CV) D C L SYMBOL A A1 A2 b C D E e MIN 1.00 -- 0.70 0.35 0.10 2.70 1.40 2.60 0.37 1 MAX 1.30 0.10 0.90 0.50 0.25 3.10 1.80 3.00 -- 9 HE e 1 A2 A 1.90 (TYP) A1 b H L 1 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 |
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