SS8051 Micro-Power Step-up DC/DC Converter FEATURES DESCRIPTION Configurable output voltage up to 28V The SS8051 boost converter is designed for small to Quiescent current of 20µA medium size LCD panels requiring high bias voltages. Shutdown current <1µA Shutdown-pin current <1µA With a typical quiescent current of 20µA and a supply Supply range from 2.5V to 6.5V voltage range of 2.5V to 6.5V, it is suitable for battery Low VDS(on): 250mV (ISW =300mA) powered portable applications, such as PDAs and Tiny SOT23-5 package handheld computers. When the SS8051 goes into shutdown mode, it consumes less than 1µA. Furthermore, with a 350mA current limit, 500ns fixed APPLICATIONS minimum off-time and tiny SOT23-5 package, the STN/TFT LCD Bias SS8051 can be used with smaller inductors and other Personal Digital Assistants (PDAs) surface-mount components to minimize the required PCB Handheld Computers footprint in space-conscious applications. Digital Still Cameras To control the SS8051, no other external current is Cellular Phones needed for the shutdown pin, which typically consumes WebPad less than 1µA over the full supply range. White LED Driver Local 3V to 5V Conversion TYPICAL APPLICATION CIRCUIT 10uH 20V 2.5V – 4.2V 12mA VCC SW 1M SS8051 SHDN FB 1µF 62k 4.7µF Rev.2.01 6/06/2003 GND www.SiliconStandard.com 1 of 9 SS8051 PIN CONFIGURATION ORDERING INFORMATION SW SS8051TXXXX VCC 1 Packing type TR: Tape and reel TB: Tube SS8051T11 5 GND 2 FB Pinout type T11 T12 SOT23-5 TOP VIEW Example: SS8051T12TR T12 pin configuration shipped in tape and reel packing SHDN 4 3 FB SHDN 1 SS8051T12 5 VCC 2 GND SW 3 4 PIN DESCRIPTION NAME SW GND FB SHDN VCC FUNCTION Switch Pin. The drain of the internal NMOS power switch. Connect this pin to inductor. Ground. Feedback Pin. Set the output voltage by selecting values for R1 and R2 (see Block Diagram): VOUT -1 R1 = R2 1. 2 Active-Low Shutdown Pin. Tie this pin to logic-high to enable the device or tie it to logic-low to turn the device off. Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. ABSOLUTE MAXIMUM RATINGS SW to GND…………………………………………………................……..-0.3V to +30V FB to GND…………………………………………………….................…..-0.3V to VCC VCC, SHDN to GND..................................................................................-0.3V to +7V Operating Temperature Range............................................................. -40°C to 85°C Maximum Operating Junction Temperature.................................................... +125°C Storage Temperature Range .............................................................. -65°C to 150°C Maximum Lead Temperature (Soldering, 10sec)............................................ +300°C Rev.2.01 6/06/2003 www.SiliconStandard.com 2 of 4 SS8051 ELECTRICAL CHARACTERISTICS (VCC = 3.6V, V SHDN = 3.6V, TA = 25°C) PARAMETER CONDITIONS MIN 2.5 Input Voltage Range Quiescent Current Switch Off Time Switch VDS(ON) 20 30 µA V SHDN = 0V 0.1 1 µA 1.2 1.22 V 1.18 2.5V<VIN<6.5V Pin Current SHDN Input Voltage High SHDN Input Voltage Low Switch Leakage Current -0.05 VFB = 1.2V 30 %/V 80 nA VFB > 1V 500 ns VFB < 0.6V 1.6 µs ISW = 300mA 250 350 mV 350 400 mA 0.1 1 µA Switch Current Limit SHDN UNITS V Not switching FB Comparator Trip Point Output Voltage Line Regulation FB Pin Bias Current (Note 2) TYP MAX 6.5 300 0.9 Switch off, VSW = 28V V 0.01 0.25 V 5 µA Note 1: The SS8051 is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the -40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 2: Bias current flows into the FB pin. Rev.2.01 6/06/2003 www.SiliconStandard.com 3 of 4 SS8051 TYPICAL PERFORMANCE CHARACTERISTICS (V CC =+3.6V, V SHDN =+3.6V, L=10µH, TA=25°C, unless otherwise noted.) Output Voltage vs. Load Current 21 20.5 20.5 Output Voltage (V) Output Voltage (V) Output Voltage vs. Input Voltage 21 IOUT =1mA 20 IOUT=10mA 19.5 V IN=2.7V 20 V IN=4.2V 19.5 19 19 2.5 3 3.5 4 4.5 5 5.5 1 2 3 5 6 7 8 9 10 Quiescent Current vs. Temperature Efficiency vs. Load Current 50 90 Quiescent Current (µA) V IN=4.2V 85 80 Efficiency (%) 4 Load Current (mA) Input Voltage (V) V IN=3.6V 75 70 V IN=2.7V 65 60 40 V IN=4.2V 30 20 V IN=2.7V 55 10 50 0.1 1 10 -20 100 0 40 60 80 100 Feedback Voltage vs. Temperature Vds(on) vs. Temperature 1.22 Feedback Voltage (V) 500 Switch Vds_on (mV) 20 Temperature (C) Load Current (mA) 400 VIN=2.7V 300 200 1.21 V IN=2.7V 1.2 1.19 V IN=4.2V V IN=4.2V 1.18 100 -20 0 20 40 60 80 100 -20 Rev.2.01 6/06/2003 0 20 40 60 80 100 Temperature (C) Temperature (C) www.SiliconStandard.com 3 of 4 SS8051 TYPICAL PERFORMANCE CHARACTERISTICS (cont.) FB Bias Current vs. Temperature Switch Current Limit vs. Temperature 450 V IN =2.7V Peak Current (mA) Feedback Bias Current (nA) 30 25 20 V IN =4.2V 400 350 V IN =2.7V 300 250 15 -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 Temperature (C ) Temperature (C ) Line Transient Rev.2.01 6/06/2003 V IN =4.2V Load Transient www.SiliconStandard.com 3 of 4 SS8051 BLOCK DIAGRAM L1 V IN VOUT C2 C1 VCC BIAS VOUT R1 SHUTDOWN LOGIC PUMP CONTROL OC DRIVER COMP ERROR COMP FB + SW SHDN en_sw + R2 1.2 V T OFF P U L S E CONTROL VREF GND APPLICATIONS INFORMATION TABLE 1. RECOMMENDED INDUCTORS The SS8051 is a boost converter with an integrated N-channel MOSFET (refer to the block diagram above). PART VALUE? µH) MAX DCR ? W) The boost cycle is initiated when the FB pin voltage drops LQH3C4R7 4.7 0.26 below 1.2V and the MOSFET turns on. During the period LQH3C100 10 0.30 that the MOSFET is on, the inductor current ramps up LQH3C220 22 0.92 until the 350mA current limit is reached. Then the CD43-4R7 4.7 0.11 MOSFET turns off and the inductor current flows through CD43-100 10 0.18 CDRH4D18-4R7 4.7 0.16 CDRH4D18-100 10 0.20 DO1608-472 4.7 0.09 DO1608-103 10 0.16 DO1608-223 22 0.37 the external schottky diode, ramping down to zero. During the MOSFET off period, the inductor current charges the output capacitor and the output voltage climbs. This pumping mechanism continues cycle by VENDOR Murata www.murata.com Sumida www.sumida.com Coilcraft www.coilcraft.com cycle until the FB pin voltage exceeds 1.2V and the non-switching mode starts. In this mode, the SS8051 Inductor Selection – Boost Regulator consumes as little as 20uA typically, saving on battery The appropriate inductance value for the boost regulator power. application may be calculated from the following equation. Select a standard inductor close to this value. Choosing an Inductor There are several recommended inductors that work well with the SS8051 in Table 1. Use the equations L= VOUT-VIN(MIN)+VD ILIM x tOFF and recommendations in the next few sections to find the proper inductance value for your design. Rev.2.01 6/06/2003 www.SiliconStandard.com 3 of 4 SS8051 Here, VD = 0.4V (Schottky diode voltage), ILIM = 350mA without any problem, but the total efficiency will suffer. and tOFF = 500ns. A larger value can be used to slightly For best performance, the IPEAK is best kept below increase the available output current, but limit it to about 500mA. twice the calculated value. When too large an inductor is used, the output voltage ripple will increase without Capacitor Selection providing much additional output current. In conditions of Low ESR (Equivalent Series Resistance) capacitors varying VIN, such as battery power applications, use the should be used at the output to minimize the output minimum VIN value in the above equation. A smaller ripple voltage and the peak-to-peak transient voltage. value can be used to give smaller physical size, but overshoot of the inductor current will occur (see Current Limit Overshoot section). Multilayer ceramic capacitors (MLCC) are the best choice, as they have a very low ESR and are available in very small packages. Their small size makes them a good match with the SS8051’s Inductor Selection – SEPIC Regulator For a SEPIC regulator using the SS8051, the approximate inductance value can be calculated using the formula below. As for the boost inductor selection, a SOT-23 package. If solid tantalum capacitors (like the AVX TPS, Sprague 593D families) or OS-CON capacitors are used, they will occupy more volume than ceramic ones and the higher ESR increases the larger or smaller value can be used. output ripple voltage. It is important to use a capacitor with a sufficient voltage rating. L=2 VOUT + VD x tOFF A low ESR surface-mount ceramic capacitor also ILIM makes a good selection for the input bypass capacitor, which should be placed as close as possible to the Current Limit Overshoot SS8051. A 4.7µF input capacitor is sufficient for The SS8051 uses a constant off-time control scheme; most applications. the MOSFET is turned off after the 350mA current limit is reached. When the current limit is reached and the MOSFET actually turns off, there is a 100ns delay time. Diode Selection During this time, the inductor current exceeds the current For most SS8051 applications, the high switching limit by a small amount. The formula below can calculate frequency requires high-speed Schottky diodes, such the peak inductor current. as the Motorola MBR0530 (0.5A, 30V) with their low IPEAK = ILIM + VIN(MAX) – VSAT L x 100ns forward voltage drop and fast switching speed. Many different manufacturers make equivalent parts, but make sure that the component is rated for at least Here, VSAT = 0.25V (switch saturation voltage). For 0.35A. To achieve high efficiency, the average systems with high input voltages and smaller current rating of the Schottky diodes should be inductance values, the current overshoot will be most greater than the peak switching current. Choose a apparent. This overshoot can be useful as it helps reverse breakdown voltage greater than the output increase the amount of available output current. By voltage. using a small inductance value, the current limit overshoot can be quite high. Even though it is Lowering Output Ripple Voltage internally current limited to 350mA, the internal The SS8051 supplies energy to the load in bursts by MOSFET of the SS8051 can handle larger currents ramping up the inductor current, then delivering that current to the load. Using low ESR capacitors will help Rev.2.01 6/06/2003 www.SiliconStandard.com 3 of 4 SS8051 minimize the output ripple voltage, but proper output ripple, increase the output capacitance value, selection of the inductor and the output capacitor also or add a 10pF feed-forward capacitor in the feedback plays a big role. If a larger inductance value or a network of the SS8051 (see the circuits in the smaller capacitance value is used, the output ripple Typical Applications section). To add this small voltage will increase because the capacitor will be inexpensive 10pF capacitor will greatly reduce the slightly overcharged each burst cycle. To reduce the output voltage ripple. TYPICAL APPLICATION CIRCUITS Boost Converter SEPIC Converter L1:MURATA LQH3C4R7M24 D1:MOTOROLA MBR0520 L1 4.7uH L1 10uH D1 C3 1uF L1,L2:MURATA LQH3C100K24 D1:MOTOROLA MBR0520 D1 1 5V 50mA V IN 2.5V to 4.2V VCC SW VCC SW 3.3V 60mA V IN 2.5V to 4.2V VCC SW 390k L2 10µH R1 SHDN FB SHDN FB C1 4.7µF C2 22µF SHDN 120k GND C1 4.7µF R2 L1 10uh/0.5A 470k R1 C2 22µF FB GND 270k R2 D1 VBAT 2.5V~5.5V MBR0530 C1 4.7µF VCC SW C2 1µF D2(Optional) 27V SS8051 ON/OFF Control FB SHDN GND White LED Driver R3 308k 1% R2 120k_1% VBIAS(+3.3V) R4 660k 1% R1 30_1% PWM Dim PWM Dimming Control VH=3.3V VL=0V Freq=160~240Hz Rev.2.01 6/06/2003 Dimming Ratio>50:1 Drive 2~8 White LEDs www.SiliconStandard.com 3 of 4 SS8051 PACKAGE DIMENSIONS SOT-23-5 (unit: mm) DIMENSIONS IN MILLIMETERS C D SYMBOLS MIN NOM MAX A 1.00 1.10 1.30 A1 0.00 ----- 0.10 A2 0.70 0.80 0.90 L E H θ1 e1 e A A2 b A1 b 0.35 0.40 0.50 C 0.10 0.15 0.25 D 2.70 2.90 3.10 E 1.40 1.60 1.80 e ----- 1.90(TYP) ----- e1 ----- 0.95 ----- H 2.60 2.80 3.00 L 0.37 ------ ----- ?1 1º 5º 9º 1. Package body sizes exclude mold flash protrusions or gate burrs 2. Tolerance ±0.1000 mm (4mil) unless otherwise specified 3. Coplanarity: 0.1000mm 4. Dimension L is measured in gage plane Feed direction SOT-23-5 package orientation Information furnished by Silicon Standard Corporation is believed to be accurate and reliable. However, Silicon Standard Corporation makes no guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its use. Silicon Standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of Silicon Standard Corporation or any third parties. Rev.2.01 6/06/2003 www.SiliconStandard.com 4 of 4