LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch GENERAL DESCRIPTION FEATURES The LSP6501 is a current mode step up converter that can carry out 1.6A. LSP6501 also builds up a internal switch with 0.23 to provide a high efficient regulator with fast response. The LSP6501 can be operated at 640KHz or 1.3MHz allowing for small filter solution and low noise. An external compensation pin gives the user flexibility in setting up loop compensation, which allows to use a low- ESR ceramic output capacitors. Internal Soft-start function results in small inrush current and the sofe-start can be programmed with an external capacitor. 1. 1.6A, 0.23, Internal Switch 2. Input Range: +2.6V to +5.5V 3. Low Shutdown Current: 0.1uA 4. Adjustable Frequency: 640kHz or 1.3MHz 5. Small 8-Pin MSOP Package TYPICAL APPLICATIONS The LSP6501 device includes under-voltage lockout, and current limiting protection preventing damage in the event of an output overload. A low profile 8-pin MSOP packages is available in the LSP6501. TFT-LCD Power Management Portable DVD Player Power Management PIN ASSIGNMENT COMP 1 8 SS FB 2 7 FREQ SHDN 3 6 VDD GND 4 5 SW MSOP-8 (Top View) PIN DESCRIPTION Pin Name Function 1 COMP Compensation Pin for Error Amplifier 2 FB 3 SHDN 4 GND 5 SW Switch Pin 6 VDD Power Supply Pin 7 FREQ 8 SS Feedback Pin with a Typical Reference Voltage of 1.24V, VOUT = 1.24x(1+ R1/R2). Shutdown Control Pin. When SHDN is Low, the LSP6501 Will Turn Off Ground Frequency Select Pin. Oscillator Frequency to 640kHz When FREQ is Low, and 1.3MHz When FREQ is High Soft-Start Control Pin. 1/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch TYPICAL APPLICATION CIRCUIT VIN 2.6 ~ 5.5VDC VOUT L CIN VCC FREQ R3 DF SW A304 LSP6501 R1 COUT C3 FB COMP SS CP2 GND R2 CP1 CSS RP ABSOLUTE MAXIMUM RATINGS Parameters Value Unit SW to GND 18 V 6 V -0.3 ~ VDD + 0.3 V 2.3 A -20 ~ +85 C Input Voltage: SHDN / VDD / FREQ to GND SS to GND SW pin maximum current Operating temperature C Maximum Operating Junction Temperature, TJ 150 -45 to 125 Storage Temperature Range C C Lead Temperature (Soldering, 10 seconds) 260 Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. THERMAL IMPEDIENCE Thermal Resistance from Junction to Ambient, JA 152C /W ELECTRICAL CHARACTERISTICS __________ (VDD=SHDN=3V, FREQ=GND; TA=25C, unless otherwise noted) Parameter Symbol Conditions Input Voltage Range VDD VDD Under voltage Lockout UVLO When VDD is rising, typical hysteresis is 40mV; SW remains off below this level Quiescent Current IDD VFB=1.3V, Not switching VFB=1.0V, switching Min Typ Max Unit 5.5 V 2.38 2.52 V 0.21 1.2 0.35 5.0 mA mA 2.6 2/10 2.25 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch Shutdown Current ISC FB Reference Voltage VFB FB Input Current FB Voltage Line Regulation Error Amp Transconductance* Ibias __________ SHDN = GND 1.228 VFB=VREF 0.1 10 uA 1.24 1.252 V 1 40 nA COMP=FB, 2.6VVDD5.5V - 0.1 0.15 %/V ICOMP=5uA 70 105 240 uA/ V - 1500 - V/V FREQ=GND 540 640 740 FREQ=VDD 1100 1320 1600 FREQ=GND 79 85 92 Gm Error Amp Gain* AV Oscillated Frequency Fosc Maximum Duty Cycle DMAX Current Limit ILIM VDD=1V, D=0.65 ON-Resistance RON Leakage Current ISWOFF FREQ=VDD 85 1.2 Iss Input Low Voltage 2.3 A Isw=1.2A 0.23 0.5 VSW=12V 0.01 20 uA 300 7 uA 0.3VDD V Vss=1.2V Input High Voltage 1.5 4 __________ VIL SHDN, FREQ; VDD=2.6V to 5.5V. __________ VIH SHDN, FREQ; VDD=2.6V to 5.5V. 0.7VDD __________ Hysteresis IFREQ SHDN Input Current Ishutdown V 0.1VDD SHDN, FREQ; FREQ Pull-Down Current % 1.6 Reset Switch Resistance Soft Start Charge current kHz 1.8 V 5.0 9.0 uA 0.001 1 uA *: Guaranteed by design, not 100% tested in production. FUNCTIONAL BLOCK DIAGRAM 5 SW FREQ 7 LOGIC S CONTROL Oscillator Sync Switch Driver R SHDN Ramp Summer 3 Slope Compensation Current Sense 4 GND 63m FB 2 1.24V Reference Error Amp 6 VDD PWM Comparator 8 SS COMP 1 3/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch TYPICAL CHARACTERISTICS Unless otherwise specified, TA = 25C. Efficiency vs. Output Current Efficiency vs. Output Current 100% 100% Fose=640KHZ L=4.7uH Fose=1.2MHZ L=4.7uH V IN =5V V IN =5V 90% 90% V IN =3.3V V IN =3.3V V IN =2.7V 70% 70% 60% 60% 50% 50% 40% 40% 0 40 80 120 160 0 200 40 10.0 Fosc=640KHZ VIN=3.3V 9.0 Output Voltage (V) Output Voltage (V) 120 160 200 Output Voltage vs . Load Curre nt Output Voltage vs . Load Curre nt 10.0 80 Output Current (mA) Output Current (mA) 8.0 Fosc=1.2MHZ VIN=3.3V 9.0 8.0 7.0 7.0 0 40 80 120 160 0 200 40 80 120 160 200 Load Current (mA) Load Current (mA) M ax Load Curre nt vs . Input Voltage Curre nt Lim it vs . Duty Cycle 900 2.4 L=4.7uH 2.2 VIN=3.3V L=4.7uH 790 Output Current (mA) 1.2MHZ Limit Current (A) V IN =2.7V 80% Efficiency Efficiency 80% 2.0 1.8 640KHZ 1.2MHZ 680 640KHZ 570 460 1.6 1.4 350 20% 40% 60% 80% 2.5 Duty (%) 3.0 3.5 4.0 4.5 5.0 Input Voltage (V) 4/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch FUNCTION DESCRIPTION VIN 2.6 ~ 5.5VDC VOUT L CIN VCC FREQ R3 DF SW LSP6501 A304 R1 COUT C3 FB COMP SS CP2 CP1 RP C.R NO Q'TY 1 1 1 2 1 1 1 1 1 1 1 1 1 IC DF CIN COUT L R1 R2 RP (R3) *NOTE 2 (C3) *NOTE 2 (CP1) CP2 CSS GND R2 CSS Value 10uF / 10V 10uF / 25V 4.7uH *NOTE 1 12K 10K (Optional) (Optional) (Optional) 10nF 1uF Description LSP6501 Schottky Diode 40V/2A CAP CER SMD CAP CER SMD 1.0A NR4018-100M Chip Resistor / 1% Chip Resistor / 1% Chip Resistor / 1% Chip Resistor / 1% CAP CER X7R CAP CER X7R CAP CER X7R CAP CER X7R Package MSOP-8 SMA SMD 1206 SMD 1206 SMD SMD 0603 SMD 0603 SMD 0603 SMD 0603 SMD 0603 SMD 0603 SMD 0603 SMD 0603 *NOTE 1: VOUT=VFB(1+R1/R2) *NOTE 2: R3 & C3 & CP1 are used for improving the transient performance. Because the components are not ideal, sometimes the system needs R3 & C3 & CP1 to get better transient. The value is determined according to real load conditions. 1. Setting the Output Voltage FB pin is used to set the output voltage VOUT of the LSP6501. By using the resistor divider, R1 and R2, to divide VOUT to the FB pin as feedback signal, the output voltage is determined by: V FB = VOUT R2 R1 + R 2 R V OUT = V FB 1 + 1 = 1 .24V R 2 R 1 + 1 R 2 Where, the feedback pin voltage, VFB, is fixed at 1.24V. 2. Selection of Output Capacitor It is recommended to select output capacitors that the capacitance is high enough and the ESR (Effective Series Resistance) is low enough. These (high capacitance & low ESR) are very important for the Boost Converter to be able to meet the VOUT ripple and load transient specifications. Ceramic capacitors often have low ESR and can meet the Boost Converter requirements as long as the capacitance values are enough. Note that the capacitance values of all kinds of ceramic capacitor drop when 5/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch there are DC voltages bias on them. The higher the DC bias, the lower the effective capacitance. The Zxx series capacitors (ex: Z5U) often drop more capacitance than what Yxx series capacitors (ex: Y5V) will drop. And Yxx series are usually worse than Xxx series (ex: X5R). Therefore, it is better to use X5R/X7R type of ceramic capacitors and don't use Yxx series (ex: Y5V) or Zxx series (ex: Z5U) types of capacitor. Although they could be cheaper than X5R or X7R, Yxx series and Zxx series' permanence is not as good as X5R/X7R and is easier to have problems like audio noise problem. The lifetime of a ceramic capacitor is shorter if the DC-bias is close to its maximum DC rating. For example, to a VOUT=12V application, a 25VDC capacitor should have a longer lifetime than a 16VDC capacitor does, even when other characteristics of these two capacitors are similar. Electrolytic capacitors have higher ESR than what ceramic capacitors do. If electrolytic capacitors are used as output capacitors, the ESR should be low enough to meet the VOUT ripple voltage requirement: ESR << VOUT Ripple ( Peak to Peak Voltage) I OUT Ripple For example, if the VOUT ripple voltage of a 5V output DC/DC converter should be smaller than 250mVPeak-to-Peak and if the ripple current is 0.5A, an capacitor whose ESR is << (0.25V/0.5A)500m should be chosen. A 680uF of ESR<500 m capacitor can be used in this case. Note that the ESR of electrolytic capacitor is highly dependent on the temperature - the lower the temperature the higher the ESR and vice versa. This temperature dependence causes VOUT ripple problem and system stability problem sometimes. It may need to use tantalum capacitors or other capacitors that the ESR are temperature independent for applications that temperature ranges are wide. It is important to ensure the ripple current rating of the output capacitor is enough or the capacitor might burn out during operation. To most electrolytic capacitors, the body temperatures should not be higher than environment temperature plus 10C. If the body temperature of the capacitor is too high, the ripple current could be higher than the rating of the capacitor. For example, if the air temperature that close to the input capacitor is 45C, it is better that the body temperature is << (45C + 10C ) = 55C. 3. Selection of Input Capacitor It is recommended to put a ceramic capacitor(s) of several uF to 10uF as input capacitor of the Boost Converter. The capacitor(s) is better to be X7R/X5R type. 4. Selection of Inductor It is recommended to use ferrite core as the chock material. Don't use iron powder core because the core loss will be too high for applications that the operation frequency is larger than 300KHz, although the cost of an iron powder core could be cheaper. The DC-R of the chock wire should be as low as possible to reduce the power loss. Below is an equation about the inductor value: L=( V IN , MIN VOUT )2 ( VOUT - V IN , MIN I OUT , MAX f SW ) (3 ) Where, L : Inductor Value ( H ) V IN , MIN : Minimum Input Voltage (V ) VOUT : Typical Output Voltage (V ) I OUT , MAX : Maximum Output Current ( A) f SW : Switching Frequency ( Hz ) : Typical Efficiency Using a higher value inductor can reduce the power loss of the Boost converter. Anyway, a higher value inductor often is bigger in size or has higher DC-R, and the higher DC-R may increase the inductor power loss. Shielding inductor has better EMI performance but the DC-R is often higher than non-shielding inductors of the same size. It is recommended to adopt an inductor value that the DC/DC converter will not transfer from 6/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch Discontinue-Current-Mode (DCM) to Continue-Current-Mode (CCM) or vise versa when VIN or IOUT change. Such mode changing will cause the duty cycle of the Boost DC/DC converter becomes unstable. 5. Selection of Flywheel Diode An Schottky diode that the voltage rating larger than 20V and the current rating larger than IOUT is recommended. Adopt a Schottky diode of lower dropout voltage can improve the system efficiency. Please also check the leakage current specification of the Schottky diode at the same time. Note that the maximum working temperatures of many Schottky diodes are only 120C. Please double check the working temperature of the Schottky diode to ensure it is within the specification. 6. Minimum & Maximum Duty Cycle Limitation PWM ICs often have trouble to convert a VOUT from a VIN if the duty cycle is too small (close to 0%) or too big (close to 100%). Small duty cycle happens when VOUT/VIN is low and big duty cycle happens when VOUT/VIN is High. DC/DC converter designers need to carefully examine whether the DC/DC converter under design has such duty cycle limit problem, especially when the nominal VOUT/VIN is already <1.2 or >5. Note that factors like VIN deviation, component value deviation, temperature change, switching frequency deviation...etc, can push the duty cycle to be much higher/lower than what we expect from the nominal VOUT/VIN values. For example, the duty of a 3.3V input, 12V output DC/DC converter seems to be around 72.5%, but the actual duty cycle could be up to 80% if we include the voltage drops of output Schottky, VIN trace drop, VIN ripple voltage drop, inductor line drop ...etc. LAYOUT GUIDE LINE PCB layout is an important stage for power circuit, especially the switching type DC/DC converter that providing high current/voltage and using high switching frequency. If PCB layout is not carefully done, the Boost converter may be unstable or cause serious EMI problems. Use wide, short, and straightforward traces for high current paths. About the input capacitors, two or more ceramic capacitors of several uF or bigger are recommended to be used. Place one of them very close to the VIN pin of IC and ground, and at least one another very close to the inductor. It is very important to keep the loop of the SW pin, Schottky diode, output capacitor, and the GND pin of LSP6501 as small as possible, and also minimize the length of the traces between these components, as shown in the following Fig. 1. This is because the di/dt at these traces is very high and according to the formula of v = L di dt the related voltage spikes will be very high if the trace inductance is high. Such voltage spikes not just cause EMC problems, but may interfere or even damage the IC sometimes. The most important is, it is better NOT to use via holes in the loop described above, because via holes have high inductance. 7/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch The loop needs to be as small as possible. L DF VIN VOUT CIN VDD FREQ ON/OFF COUT SW GND A304 LSP6501 SHDN CP1 CP2 FB SS COMP CSS R1 R2 RP Fig. 1 Second, keep all the analog components and signal traces, for example the VOUT sense trace, far away from the noisy areas, that is, the areas near inductor, LSP6501 switch pin, and Schottky diode. If the VOUT sense trace is close to the noisy area, large noise may be coupled into FB pin and cause VOUT value not accurate or unstable. Please refer to Fig. 2. Noisy area. L DF VIN VOUT CIN COUT VDD FREQ ON/OFF SHDN SW GND LSP6501 A304 SS COMP CSS CP2 RP FB R1 R2 CP1 Analog components & traces should be far away from noisy area. Fig. 2 About analog ground (the ground for feedback resistors, soft start capacitor, VOUT sensing resisters, and compensation components), it is recommended to use short traces to connect these ground points and then directly connect these traces to the GND pin of the IC. Please refer to Fig. 3 & Fig. 4. 8/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch L DF CIN FREQ SHDN CIN SW SS COMP RP ON/OFF R2 CP2 RP CP1 Analog ground is independent with power ground. It is also short and far away from noisy area. SHDN SW A304 LSP6501 SS (Good) FB R1 R2 CP1 It is bad to use other ground trace as analog ground. It is even worse if the traces are long, close to noisy area or connected to high current devices. Load 2 Load 1 GND COMP CSS CP2 FREQ R1 FB VOUT COUT VDD Load 1 GND A304 LSP6501 DF VIN COUT VDD ON/OFF L VOUT VIN CSS Load 2 (Bad) Fig. 3 Fig. 4 A big ground plane (form input to out put) can help almost all the performance of the chip. Beside the ground trace on the top layer, please use another layer as the ground layer. ORDERING INFORMATION LSP6501X X X X Package: MS: MSOP8L Output Voltage: Blank: Adj Packing: A: Tape & Real Temperature Grade: C: -2085 MARKING INFORMATION MSOP-8 LOGO LSC LSP6501 VYWZ Part ID 9/10 VER. 1.2 LSP6501 1.6A, 1.3MHz, Boost DC-DC Converter With Internal Switch PACKAGE INFORMATION A J B INCHES MILLIMETERS MIN TYP MAX MIN TYP MAX A 0.114 0.118 0.122 2.9 3 3.1 B 0.114 0.118 0.122 2.9 3 3.1 C 0.043 D F 0.021 F M 1.1 0.012 0.016 P D G 0.3 0.031 0.4 0.53 G 0.026BSC 0.65BSC J 0.006 0.15 0.8 C K K 0 - 0.006 0 - 0.15 M 0 - 8 0 - 8 P 0.185 0.193 0.201 4.7 4.9 5.1 10/10 VER. 1.2