LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET KEY FEATURES DESCRIPTION Internal Reference 1.17V ±2% Accuracy (Line and Temperature) 4V to 6.0V Input Range Adj. Output From 1.17V to VIN Output Current (IDC >850mA) Quiescent Current < 300µA 1MHz Operation Frequency MSOP 8-Pin APPLICATIONS/BENEFITS WWW . Microsemi .C OM The LX1910 does not require a minimum load current for stable operation. There is no Under Voltage Lockout for the input voltage, operational range includes 4V to 6V. The regulator is capable of providing an output dc load current of 850mA. The SHDN pin places the device in a sleep-mode drawing less than 1µA of quiescent current. The LX1910 comes in space-saving MSOP package allowing a complete application circuit to occupy a very small PCB area. These features make the LX1910 ideal for use in SmartPhones, PDAs, or other batteryoperated devices The LX1910 PWM buck regulator achieves very high efficiencies over a broad range of operating load conditions. The LX1910 implements a load-detection architecture and enters a power-saving PFM mode when driving small load currents ensuring optimal regulator efficiency over the entire output current range thus maximizing battery life. The PWM operating mode implements a fixed frequency of 1MHz (typ), the transconductance error amplifier has 12µA of drive with an output voltage swing rail to rail. Compensation is external for maximum user flexibility. Portable Microprocessor Core Voltage Supplies 5V to 3V IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com PRODUCT HIGHLIGHT LX1910 Efficiency @ Vout=1.5V 90% LX1910 PVIN VOUT SW AVIN SHDN CIN RC D COMP FB AGND PGND CX R1 COUT R2 CC CONVERSION EFFICIENCY VIN 80% L 70% 60% 50% 40% 30% 20% 10% 0 100 200 300 400 500 600 700 OUTPUT CURRENT, mA Figure 1 – LX1910 Circuit Topology and Typical Efficiency Performance PACKAGE ORDER INFO Input Voltage Output Voltage Range 0 to 85 4.5V – 6.0V 1.17V to VIN DU Plastic MSOP 8-PIN LX1910 TJ(°C) RoHS Compliant / Pb-free LX1910CDU Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1910-13016CDU-TR) Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET ABSOLUTE MAXIMUM RATINGS PACKAGE PIN OUT Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of specified terminal. PVIN AVIN SHDN COMP 1 8 2 7 3 6 4 5 SW PGND AGND FB DU PACKAGE (Top View) RoHS / Pb-free 100% Matte Tin Lead Finish THERMAL DATA WWW . Microsemi .C OM Input Voltage (IN) or SHDN to GND .............................................................................-0.3V to 7.0V SW to GND.............................................................................................................-0.3V to (VIN + 0.3V) VFB to GND..........................................................................................................................-0.3V to +2V SW Peak Current (Internally Limited) ....................................................................................... 1000mA Operating Temperature Range.......................................................................................-40°C to +125°C Storage Temperature Range, TA ...................................................................................... -65°C to 150°C Maximum Junction Temperature.................................................................................................... 150°C RoHS / Pb-free Peak Package Solder Reflow Temperature (40 seconds maximum exposure) ......................................................................................260°C (+0, -5) DU Plastic MSOP 8-Pin THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA 206°C/W Junction Temperature Calculation: TJ = TA + (PD x θJA). The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. FUNCTIONAL PIN DESCRIPTION NAME SW DESCRIPTION Inductor and commutation diode connection point. Connects to internal MOSFET drain. AGND Analog circuit ground providing bias for IC operation. FB Feedback input for setting adjustable output voltage SHDN PVIN COMP Enable control input. Reduces quiescent current to 1µA. Pin 8, Output becomes high impedance. Unregulated supply voltage input connected to PMOS Source. Input range from +2.7V to 6.0V Frequency Compensation of the overall loop is effected by placing a series R/C combination between COMP pin and GND. AVIN Unregulated supply voltage input. Input range from +4V to 6.0V PGND Power ground (return path for internal PMOS gate driver). PACKAGE DATA Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET ELECTRICAL CHARACTERISTICS Specifications apply over junction temperature of: 0oC < T < 85oC for VIN = 5V (except where otherwise noted). Typical values are at TA=25°C. Symbol VIN Test Conditions Functional operation guaranteed by design Output Voltage Range VOUT Closed loop operating range Feed Back Threshold VFBT 4V < VIN < 6V FB Input Current IFB EA Drive Current (COMP Pin) ISOURCE ISINK EA Output Swing (COMP Pin) Quiescent Operating Current Sleep (Shutdown Mode) Current VEA OUT IQ P-Channel Switch ON Resistance Maximum Duty Cycle RDS(ON) D V 0.95*VIN V 1.170 1.193 V 300 500 nA 10 16 VFB +125mV of Overdrive, VCOMP = 2.5V 10 16 µA 95 mV VOH, Sourcing 10µA 4.86 V Pin 2 Supply Current 250 VOL, Sinking 10µA VSHDN = 0V, SW grounded VSD Units 6.0 VFB -125mV of Overdrive, VCOMP = 2.5V IQVINSD Shutdown Voltage Threshold VFB 1.146 Max µA VSHDN = 0V, SW Pin open ISD_IB Typ 3.5 VFB = 1.2V IQVINSD Shutdown Input Bias Current Min 2 SHDN = GND or SHDN = 5V -100 Device Off Device On µA 1 µA 5 µA 100 nA 0.2*VIN V V 0.8*VIN ISW = 0.5A 0.53 0.8 Ω 80 100 SW Leakage Current P-Channel Current Limit ILEAK ILIM 5 900 1 950 µA mA Frequency FOP 0.80 1.07 1.2 MHz 0.35 0.5 % VO Closed Loop Load Regulation Thermal Shutdown Load Reg ISW = 0.5A (assured by design, not ATE tested) 400 VO = 1.5V, 5mA < IO < 700mA, ckt figure 3 TSD 125 WWW . Microsemi .C OM Parameter Operating Range 150 % °C ELECTRICALS Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET SIMPLIFIED BLOCK DIAGRAM PVIN WWW . Microsemi .C OM AVIN Ramp SW comparator PWM + bg + avin Logic - FB agnd pgnd OSC ilimit Skip Mode SHDN Shutdown COMP Thermal Sense LX1910 PGND AGND Figure 2 – LX1910 Block Diagram LX1910 5.0V PVIN 4.7µH 1.5V SW AVIN 3300pF SHDN 4.7µF 30KΩ 14KΩ D COMP FB AGND PGND 10µF 51KΩ BLOCK DIAGRAM 3300pF Figure 3 – Circuit for 1.5V Output Voltage Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET APPLICATION NOTE OUTPUT VOLTAGE PROGRAMMING Resistors R1 and R2 program the output voltage. An optional capacitor CX may be inserted across R1 to improve the transient response (see Figure 1). The value of R2 should be less than 100KΩ. The value of R1 can be determined using the following equation, note VREF is also referred to as VFBT. ⎡⎛ V ⎞ ⎤ R1 = R2⎢⎜⎜ OUT ⎟⎟ − 1⎥ ⎣⎢⎝ VREF ⎠ ⎦⎥ DESIGN EXAMPLE: Let R2 equal 50K and the required VOUT equal to 3.0V. ⎡⎛ 3V ⎞ ⎤ ⎟⎟ − 1⎥ ⎣⎢⎝ 1.17 ⎠ ⎦⎥ R1 = 50K ⎢⎜⎜ = 78KΩ DIODE SELECTION A Schottky diode is recommended for use with the LX1910 because it provides fast switching and superior reverse recovery performance. The Microsemi UPS5817 (20V @ 1A) makes an effective choice for most applications. Copyright © 2004 Rev. 1.1, 2005-02-25 LAYOUT CONSIDERATIONS The high peak currents and switching frequencies present in DC/DC converter applications require careful attention to device layout for optimal performance. Basic design rules include: (1) maintaining wide traces for power components (e.g., width > 50mils); (2) place CIN, COUT, the Schottky diode, and the inductor close to the LX1910; (3) minimizing trace capacitance by reducing the etch area connecting the SW pin to the inductor; and (4) minimizing the etch length to the FB pin to reduce noise coupling into this high impedance sense input. Other considerations include placing a 0.1uF capacitor between the LX1910 VOUT pin and GND pin to reduce high frequency noise and decoupling the VIN pin using a 0.1µF capacitor. Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 APPLICATIONS INDUCTOR SELECTION Selecting the appropriate inductor type and value ensures optimal performance of the converter circuit for the intended application. This selection process requires the designer to make trade-offs between circuit performance and cost. A primary consideration requires the selection of an inductor that will not saturate at the peak current level. Other considerations that affect inductor choice include EMI, output voltage ripple, and overall circuit efficiency. The inductor that works best depends upon the application’s requirements. Further, some experimentation with actual devices in-circuit is typically necessary to make the most effective choice. The LX1910 allows for a broad selection of inductor values and choosing a value between 2.2µH and 30µH supports a majority of applications. Selecting a larger inductor value can increase efficiency and reduce output voltage ripple. Smaller inductors typically provide smaller package size (critical in many portable applications) at the expense of increasing output ripple current. Regardless of inductor value, selecting a device manufactured with a ferrite-core produces lower losses at higher switching frequencies and thus better overall performance. CAPACITOR SELECTION To minimize ripple voltage, output capacitors with a low series resistance (ESR) are recommended. Multi-layer ceramic capacitors with X5R or X7R dielectric make an effective choice because they feature small size, very low ESR, a temperature stable dielectric, and can be connected in parallel to increase capacitance. Typical capacitance values of 4.7 to 30µF have proven effective. Other low ESR capacitors such as solid tantalum, specialty polymer, or organic semiconductor, make effective choices provided that the capacitor is properly rated for the output voltage and ripple current. Finally, choose an input capacitor of sufficient size to effectively decouple the input voltage source impedance (e.g., CIN > 4.7µF). WWW . Microsemi .C OM FUNCTIONAL DESCRIPTION The LX1910 implements a PFM / PWM architecture that improves power management efficiency across the output load range. Page 5 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET CHARACTERISTIC CURVES CONVERSION EFFICIENCY OUTPUT DEVIATION, % 0.15% 0.10% 0.05% 0.00% -0.05% -0.10% -0.15% -0.20% -0.25% -0.30% -0.35% 0 100 200 300 400 500 600 80% 70% 60% 50% 40% 30% 20% 10% 0 700 10 20 Figure 4 1910 LINE REG (Vout=1.5V, Rload=15 ohms) 1.45 0.4% Vfb (Pin 5), Volts Vo VOLT 0.2% Vout Error 1.05 0.0% 0.95 -0.1% 0.85 -0.2% 0.75 -0.3% 1.160 0.65 -0.4% 1.155 0.55 -0.5% 3 3.5 4 Vin, volts 90 100 70 80 1.175 0.1% 2.5 80 1.180 1.15 2 70 1.185 0.3% Vo 1.5 60 Feedback Voltage Thermal Stability 0.5% 1 50 Figure 5 1.55 1.25 40 OUTPUT CURRENT, ma IOUT, ma 1.35 30 WWW . Microsemi .C OM LX1910 Efficiency @ Vout=1.5V LX1910 LOAD REGULATION (Vout=1.5V) 4.5 5 5.5 1.170 1.165 -10 0 10 20 30 40 50 60 6 Temperature, °C Figure 7 Figure 6 GRAPHS Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LX1910 TM ® Step-Down Regulator P RODUCTION D ATA S HEET CHARACTERISTIC CURVES WWW . Microsemi .C OM Figure 9– Output Load Step Response: CH1: VOUT and CH4: IOUT; Condition: VIN = 5.0V; ISTEP = 50 to 600mA Figure 10 – Switching Waveforms: PFM Mode CH3: VSW (pin 8) and CH1: VOUT; ( VIN = 5.0V; IOUT = 1mA) Figure 11 – Switching Waveforms: PWM Mode CH3: VSW (pin 8) and CH1: VOUT; (VIN = 5.0V; IOUT = 10mA) GRAPHS Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LX1910 ® TM Step-Down Regulator P RODUCTION D ATA S HEET PACKAGE DIMENSIONS 8-Pin Miniature Shrink Outline Package (MSOP) A Dim B H G P M C N Note: WWW . Microsemi .C OM DU D L K A B C D G H J K L M N P MILLIMETERS MIN MAX 2.85 3.05 2.90 3.10 – 1.10 0.25 0.40 0.65 BSC 0.38 0.64 0.13 0.18 0.95 BSC 0.40 0.70 3° 0.05 0.15 4.75 5.05 INCHES MIN MAX .112 .120 .114 .122 – 0.043 0.009 0.160 0.025 BSC 0.015 0.025 0.005 0.007 0.037 BSC 0.016 0.027 3° 0.002 0.006 0.187 0.198 Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(0.006”) on any side. Lead dimension shall not include solder coverage. NOTES MECHANICALS PRODUCTION DATA – Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not necessarily include testing of all parameters. Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. Copyright © 2004 Rev. 1.1, 2005-02-25 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8