LX1918CLD

LX1918 TM ® 1.8A Step-Down Synchronous Converter P RODUCTION D ATA S HEET DESCRIPTION KEY FEATURES Input range voltage 2.7 to 5.5V Maximum output current, 1.8A Internal or External Synchronization Output Voltage from VIN to 0.6V PFM or PWM mode under light load EMI support with force PWM mode Efficiency up to 95% No external Schottky diode Thermal shutdown Cycle by cycle switch current limit UVLO Short circuit protection 8 pin MLP APPLICATIONS The Microsemi LX1918 is a step down buck regulator with a synchronous rectifier. All MOSFET switches and compensation components are built in. The synchronous rectification eliminates the need of an external Schottky diode and maximizes efficiency (>95%) for a high step-down ratio and a low output voltage. The input supply voltage range is from 2.7V to 5.5V with a maximum output current of 1.8A. The LX1918 is a current mode PWM with optional PFM under light loads. The LX1918 can switch with a 1MHz free running internal oscillator or be synchronized with an external oscillator ranging from 500KHz to 1.25MHz; the high frequency allows for small size and low cost external components. The LX1918 output voltage is programmable with two resistors and can be tightly regulated down to 0.6V. The LX1918 MODE feature can either maximize efficiency or reduce EMI depending on the needs of the application. High efficiency (MODE = GND) is obtained by allowing the LX1918 to enter a PFM mode with discontinuous inductor current. Low EMI (MODE=VCC) is obtained by only operating in PWM mode even at no load. The LX1918 features include soft start, cycle-by-cycle switch current limit, hiccup short circuit current limiting and thermal shut down. The LX1918 comes in small 8 pin MLP package (fully RoHS compliant). WWW . Microsemi . C OM IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com Lower power embedded applications WLAN power system Portable design with single cell Lion or 3 cells NiMH/NiCd Low power portable storage application PRODUCT HIGHLIGHT VIN PWR VCC MODE SW VOUT @ 1.8 A LX1918 ON OFF E/S FB PGND SGND LX1918 LX1918 PACKAGE ORDER INFO TA (°C) -40 to 85 LD Plastic MLP 8-Pin 3x3mm LX1918CLD RoHS Compliant / Pb-free Note: Available in Tape & Reel. Append the letters “TR” to the part number.(i.e. LX1918CLD-TR) Copyright © 2004 Rev. 1.1, 2005-07-05 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LX1918 TM ® 1.8A Step-Down Synchronous Converter P RODUCTION D ATA S HEET ABSOLUTE MAXIMUM RATINGS PACKAGE PIN OUT WWW . Microsemi . C OM Supply Input Voltage (PWR, VCC)..................................................-0.3V to 6.5V Supply Input Transient Voltage (PWR, VCC).................................................10V Input Voltage (E/S, FB,MODE) ......................................... -0.3V to (VCC + 0.3V) Maximum Switch Voltage (SW)....................................... -0.3V to (VPWR + 0.3V) SW Peak Current (Internally Limited)............................................................3.6A Operating Ambient Temperature Range ........................................-40°C to +85°C Operating Junction Temperature Range.......................................-40°C to +125°C Maximum Operating Junction Temperature ................................................ 150°C Storage Temperature Range...........................................................-65°C to 150°C Peak Package Solder Reflow Temp. (40 second max. exposure) ... 260°C (+0, -5) 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. 1 FB SGND PGND SW 2 3 4 8 7 6 5 E/S MODE VCC PWR LD PACKAGE (Top View) THERMAL DATA 1918 xxxx MSC LD PACKAGE MARKINGS “xxxx” Denote Date Code and Lot Identification LD Plastic MLP 3mm X 3mm 8-Pin 35 – 50°C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA RoHS / Pb-free 100% Matte Tin Lead Finish 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. The variation in overall thermal resistance, ΘJA, is directly affected by heatsink area available on the PCB. FUNCTIONAL PIN DESCRIPTION PIN 1 2 3 4 5 6 7 8 Name FB SGND PGND SW PWR VCC MODE E/S Description Feedback Pin - This pin is regulated to the internal reference voltage. Signal Ground – Low current signal ground reference for IC; also attaches to bottom pad. Connect to common ground reference. Ground – High current ground; connects to common ground reference. MOSFET Switch (Drain) Connects for inductor. Power Input – Connect a decoupled voltage source between 2.7V and 5.5V. Reference power supply for IC. Light Load Mode Select - Ground for Highest efficiency mode or pull high for Lowest EMI mode during light load operation. Enable and External Synchronization – Pull high to enable operation with internal oscillator. Apply an external oscillator signal to synchronize the PWM switch frequency. Apply logic low to cause IC to enter Shutdown mode. PACKAGE DATA PACKAGE DATA Copyright © 2004 Rev. 1.1, 2005-07-05 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LX1918 TM ® 1.8A Step-Down Synchronous Converter P RODUCTION D ATA S HEET ELECTRICAL CHARACTERISTICS Unless otherwise specified, the following specifications apply over the operating ambient temperature2 -40°C ≤ TA where otherwise noted and the following test conditions: VIN = 3.7V; VE/S = 3.7V; VMODE = GND Parameter ENTIRE REGULATOR ≤ 85°C3 except WWW . Microsemi . C OM Symbol Test Conditions Min 2.7 LX1918 Typ 92 350 0.5 1 1 0.600 1.00 0.1 Max 6.0 500 1.0 0.612 50 1.25 1.0 0.4 1250 Units V % µA % % V nA MHz µA V kHz ns µA V A °C V Input Voltage3 Efficiency1 Quiescent Current • Active • Shutdown Line Regulation1 Load Regulation1 Feedback Voltage FB Input Current Internal Oscillator frequency E/S Pin Bias Current E/S Logic High Input E/S Logic Low Input SYNC Capture Range SYNC Minimum Pulse Width MODE Bias Current MODE Logic High MODE Logic Low SW Pin Current Limit Thermal Shutdown Threshold1 Under Voltage Lockout VPWR, VCC η VOUT = 1.8V, IOUT = 200mA ICC VE/S = 3.6V; VFB = 1.0V; T = 25°C VE/S = GND VIN = 2.7 to 5.5V IOUT = 10mA to 1.5A VFB = 0.5V to 0.7V VE/S = 3.6V; VMODE= 3.6V VE/S = GND VMODE= 3.6V High or Low; VMODE= 3.6V VE/S = GND: VMODE= VIN VMODE(HI) V MODE(LO) Peak Current VUVLO VFB IFB FOSC VE/S(HI) VE/S(LO) 0.588 -50 0.75 1.6 500 100 1.0 0.9 x VIN 2.0 130 2.7 140 2.0 0.1 x VIN 3.6 150 2.7 Notes 1. 2. 3. Guaranteed by design, but not tested. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature. Functionality over the -40°C to +85°C operating temperature range is assured by design, characterization, and correlation. ELECTRICALS ELECTRICALS Copyright © 2004 Rev. 1.1, 2005-07-05 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LX1918 TM ® 1.8A Step-Down Synchronous Converter P RODUCTION D ATA S HEET SIMPLIFIED BLOCK DIAGRAM WWW . Microsemi . C OM PWR VCC 2.7A UVLO AND ENABLE LOGIC Soft Start Ramp and Cur Limit Clamp 0mA Current Limit Slope Compensation VREF OR ADJ + FB - gm Compensation Error Amp Cur Limit Turn on Blanking R Q Thermal Overload S Q Reverse Current Detect E/S CLOCK LOGIC CCO