19-3086; Rev 0; 5/04 KIT ATION EVALU E L B A AVAIL Low Input/Output Voltage Step-Up DC-DC Converter with RESET Applications MP3 Players, Pagers, and CD Players Features ♦ Low Input (0.7V) and Output (1.8V) Voltage Capability ♦ Internal Synchronous Rectifier ♦ High 94% Efficiency ♦ Fixed Output Voltages: 1.8V, 2.5V, 3V, and 3.3V ♦ Up to 2MHz Switching Allows Small External Components and Low Output Ripple ♦ Automatic Pulse Skipping at Light Loads for Extended Battery Life ♦ Low 70µA (typ) Operating Supply Current (Measured at OUT) ♦ Low 2µA Logic-Controlled Shutdown ♦ True Shutdown Fully Discharges Output to Ground ♦ Uses Only Small Ceramic Capacitors ♦ 75ms RESET Output Flag PDAs and Organizers Ordering Information Digital Still Cameras Cordless Phones PART Wireless Mice/Keyboards TEMP RANGE PIN-PACKAGE MAX1947ETAxy* -40°C to +85°C 8 TDFN 3mm x 3mm *xy represents the output voltage code (e.g., 18 =1.8V). Standard output voltages include 3.3V (33), 3.0V (30), 2.5V (25), and 1.8V (18). Contact the factory for other output voltages in 100mV increments between 1.8V and 3.3V; the minimum order quantity is 25,000 units. Portable Medical Equipment Other Battery-Powered Systems Pin Configuration Typical Application Circuit VIN +0.7V TO +VOUT 4.7µH TOP VIEW 2.2µF VOUT +1.8V, +2.5V, +3.0V, +3.3V LX BATT OUT MAX1947 SHDN 10µF PGND RESET 1 GND 2 8 BATT 7 OUT MAX1947 GND 3 6 LX SHDN 4 5 PGND RESET GND TDFN 3mm x 3mm True Shutdown is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1947 General Description The MAX1947 is a compact, high-efficiency, step-up DCDC converter that regulates output voltages from 1.8V to 3.3V to power µP/DSP cores, memory, and I/O rails in 1and 2-cell alkaline/NiMH/NiCd battery-powered systems. It features an internal 800mA switch and synchronous rectifier to achieve up to 94% efficiency and to eliminate the need for an external Schottky diode. High-frequency switching (up to 2MHz) results in low ripple and small external components, while automatic pulse skipping at light loads reduces supply current to just 70µA for extended battery life. Maxim’s proprietary True Shutdown™ reduces supply current to just 2µA and fully discharges the output to ground. The converter is offered in fixed-output voltages of 1.8V, 2.5V, 3.0V, and 3.3V, requiring no feedback or compensation network. A 75ms RESET output flag provides for power-on reset (POR) and undervoltage detection. The MAX1947 is available in a space-saving 8-pin TDFN package. MAX1947 Low Input/Output Voltage Step-Up DC-DC Converter with RESET ABSOLUTE MAXIMUM RATINGS BATT, OUT, SHDN to GND ...................................-0.3V to +4.0V RESET to GND..........................................-0.3V to (VOUT + 0.3V) PGND to GND .......................................................-0.3V to +0.3V Switch Current (ILX, IOUT, IPGND) (Note 1) .................-1A to +1A Continuous Power Dissipation (TA = +70°C) 8-Pin TDFN (derate 24.4mW/°C above +70°C)..........................................................1951.2mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: LX has internal clamp diodes to PGND and OUT. Applications that forward bias these diodes should take care not to exceed the IC’s package power-dissipation limits. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VBATT = 1.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER Minimum Startup Voltage CONDITIONS MIN RLOAD = 1kΩ, TA = +25°C Startup-Voltage Temperature Coefficient Maximum Input Operating Voltage Load Regulation MAX UNITS 0.8 0.95 V -2.1 (Note 3) mV/°C 3.6 Minimum Input Operating Voltage Output Voltage TYP 0.7 V MAX1947ETA18, ILOAD = 40mA 1.74 1.8 1.86 MAX1947ETA25, ILOAD = 32mA 2.42 2.5 2.58 MAX1947ETA30, ILOAD = 25mA 2.9 3.0 3.1 MAX1947ETA33, ILOAD = 25mA 3.2 3.3 3.4 No load to full load VBATT = 1V Full-Load Output Current VBATT = 1.8V 1.2 MAX1947ETA18 160 273 MAX1947ETA25 130 214 MAX1947ETA30 100 185 MAX1947ETA33 100 169 MAX1947ETA25 240 380 MAX1947ETA30 200 361 MAX1947ETA33 200 329 V V % mA Supply Current into BATT No switching 2 4 µA Supply Current into OUT No switching 70 110 µA LX Switch Maximum On-Time 0.7 1 1.3 µs LX Switch Minimum Off-Time 0.2 0.25 0.3 µs Maximum On-Time to Minimum Off-Time Ratio 3.6 4 4.6 Frequency in Startup 2 650 _______________________________________________________________________________________ kHz Low Input/Output Voltage Step-Up DC-DC Converter with RESET MAX1947 ELECTRICAL CHARACTERISTICS (continued) (VBATT = 1.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER Startup to Normal-Mode Output Transition Voltage NFET Current Limit PFET Turn-Off Current Internal NFET On-Resistance CONDITIONS 50mV hysteresis, rising edge MAX UNITS 1.40 1.62 1.73 V 600 800 1000 TA = -40°C to +85°C 580 800 1000 TA = 0°C to +85°C 15 75 150 TA = -40°C to +85°C 10 75 150 MAX1947ETA18 0.3 0.6 MAX1947ETA25 0.22 0.44 MAX1947ETA30 0.17 0.34 MAX1947ETA33 0.15 0.3 MAX1947ETA18 0.5 1.0 MAX1947ETA25 0.35 0.7 MAX1947ETA30 0.28 0.56 MAX1947ETA33 0.25 0.5 TA = +25°C 0.1 1 TA = +85°C 1 ILX = 100mA SHDN = GND, VOUT = 0V, VLX = 3.6V LX Leakage Current TYP TA = 0°C to +85°C ILX = 100mA Internal PFET On-Resistance MIN mA mA Ω Ω µA SHUTDOWN MODE Shutdown Supply Current SHDN = GND VIH SHDN Input Voltage 2 OUT Discharge Resistance in Shutdown µA V 0.18 x VBATT VIL SHDN Input Bias Current 4 0.8 x VBATT SHDN = OUT or GND, TA = +25°C 1 SHDN = OUT or GND, TA = +85°C 5 SHDN = GND 100 nA 500 1000 Ω 90 93 % RESET OUTPUT Reset OUT Voltage Trip Level VOUT falling, 1% hysteresis Minimum VOUT for Valid Reset 87 0.9 Reset Timeout 65 RESET Output Voltage ISINK = 200µA ISOURCE = 200µA V 140 235 0.3 0.8 x VOUT ms V Note 2: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design. Note 3: When BATT is greater than the output-voltage set point, the part is in track mode (see the Track Mode section). _______________________________________________________________________________________ 3 Typical Operating Characteristics (VIN = 1.5V, Circuit of Typical Application Circuit, TA = +25°C, unless otherwise noted.) MAX1947ETA25 EFFICIENCY vs. LOAD CURRENT 100 VIN = 1.6V 95 VIN = 1.25V 80 75 VIN = 1V VIN = 1.25V VIN = 1V 75 80 70 65 65 60 60 100 60 1000 0.1 1 10 100 1000 0.1 1 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) MAX1947ETA33 EFFICIENCY vs. LOAD CURRENT MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE NO-LOAD INPUT CURRENT vs. INPUT VOLTAGE 85 80 75 VIN = 1.25V VIN = 1V 70 65 VOUT = 2.5V 800 VOUT = 1.8V 600 400 200 500 1 10 100 300 VOUT = 2.5V 200 1.2 1.7 2.2 2.7 3.2 3.7 0.7 1.2 1.7 2.2 2.7 3.2 INPUT VOLTAGE (V) INPUT VOLTAGE (V) STARTUP VOLTAGE vs. LOAD CURRENT STARTUP VOLTAGE vs. TEMPERATURE SHUTDOWN THRESHOLD vs. INPUT VOLTAGE VOUT = 2.5V 1.4 VOUT = 3.3V 1.2 1.0 0.8 0.6 RLOAD = 1kΩ 0.8 0.7 0.6 0.5 RLOAD = 0Ω 0.4 0.3 60 80 100 LOAD CURRENT (mA) 120 140 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.2 0.4 0.1 0.2 0 40 2.0 3.7 MAX1947toc09 VOUT = 1.8V 0.9 SHUTDOWN THRESHOLD (V) 1.8 1.0 STARTUP VOLTAGE (V) VOUT = 3.0V MAX1947toc08 LOAD CURRENT (mA) 2.0 20 VOUT = 1.8V 0 0.7 1000 MAX1947toc07 0.1 VOUT = 3.3V 400 100 VOUT = 3.3V 0 60 MAX1947toc06 MAX1947toc05 VOUT = 3.0V 1000 600 INPUT CURRENT (µA) 90 1200 MAXIMUM OUTPUT CURRENT (mA) MAX1947toc04 95 0 VIN = 1V LOAD CURRENT (mA) VIN = 2.5V VIN = 1.8V 1.6 VIN = 1.25V 75 70 100 EFFICIENCY (%) 80 85 65 10 VIN = 1.8V 90 85 70 1 VIN = 2.5V 95 EFFICIENCY (%) 85 0.1 4 VIN = 1.6V 90 EFFICIENCY (%) EFFICIENCY (%) 90 100 MAX1947toc02 95 MAX1947toc01 100 MAX1947ETA30 EFFICIENCY vs. LOAD CURRENT MAX1947toc03 MAX1947ETA18 EFFICIENCY vs. LOAD CURRENT STARTUP VOLTAGE (V) MAX1947 Low Input/Output Voltage Step-Up DC-DC Converter with RESET 0 -40 -15 10 35 TEMPERATURE (°C) 60 85 0.7 1.2 1.7 2.2 2.7 INPUT VOLTAGE (V) _______________________________________________________________________________________ 3.2 3.7 Low Input/Output Voltage Step-Up DC-DC Converter with RESET OUTPUT VOLTAGE vs. LOAD CURRENT 1.80 1.78 1.80 1.78 MAX1947toc12 1.82 OUTPUT VOLTAGE (V) 1.82 OUTPUT VOLTAGE (V) 1.82 1.84 MAX1947toc11 1.84 MAX1947toc10 1.84 1.80 1.78 1.76 1.76 1.76 1.74 1.74 1.74 ILOAD = 40mA 150 200 250 300 350 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 LOAD CURRENT (mA) -40 -15 INPUT VOLTAGE (V) HEAVY-LOAD SWITCHING WAVEFORMS VOUT (AC-COUPLED) 50mV/div VOUT (AC-COUPLED) 50mV/div VIN (AC-COUPLED) 2V/div VLX IL 500mA/div 85 50mV/div 50mV/div 2V/div IL 500mA/div 2µs/div LINE-TRANSIENT WAVEFORMS LOAD-TRANSIENT WAVEFORMS 1.5V 1V 50mV/div 10µs/div 60 VLX 2µs/div VOUT (AC-COUPLED) 35 LIGHT-LOAD SWITCHING WAVEFORMS VIN (AC-COUPLED) VIN 10 TEMPERATURE (°C) MAX1947toc14 100 MAX1947toc16 50 MAX1947toc13 0 MAX1947toc15 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE vs. TEMPERATURE NO-LOAD OUTPUT VOLTAGE vs. INPUT VOLTAGE ILOAD VOUT (AC-COUPLED) 200mA/div 50mV/div 10µs/div _______________________________________________________________________________________ 5 MAX1947 Typical Operating Characteristics (continued) (VIN = 1.5V, Circuit of Typical Application Circuit, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = 1.5V, Circuit of Typical Application Circuit, TA = +25°C, unless otherwise noted.) EXITING AND ENTERING SHUTDOWN WAVEFORMS POWER-ON RESET WAVEFORMS MAX1947toc18 MAX1947toc17 MAX1947 Low Input/Output Voltage Step-Up DC-DC Converter with RESET VIN 1V/div VOUT 1V/div VRESET 1V/div VRESET 1V/div VOUT 1V/div VSHDN 1V/div 20ms/div 20ms/div Pin Description PIN NAME FUNCTION 1 RESET 2 GND Ground. Connect to exposed paddle. 3 GND Ground. Connect to exposed paddle. 4 SHDN Shutdown Input. Connect to BATT or logic 1 for normal operation. Connect to GND or logic 0 for a low quiescent-current shutdown mode. 5 PGND Power Ground. Connect to exposed paddle. 6 LX 7 OUT Regulator Output. Bypass with 10µF ceramic capacitor to GND for full-load capability. For less than 50% of full load, a 4.7µF capacitor can be used. 8 BATT Battery Connection. VBATT is used for the startup oscillator and to power the chip when VOUT < VBATT. — EP Active-Low Push-Pull Reset Output. RESET goes high 75ms (min) after the output voltage has exceeded 90% of its final value. The RESET output is valid for output voltages as low as 0.9V. RESET is driven low in shutdown. Inductor Connection to the Drains of the Internal N-Channel Switch and P-Channel Synchronous Rectifier Exposed Paddle. Connect to GND and PGND. Detailed Description The MAX1947 compact step-up DC-DC converter starts up with voltages as low as 0.8V and operates with input voltages down to 0.7V. An internal synchronous rectifier reduces cost by eliminating the need for an external Schottky diode and improves overall efficiency by reducing losses in the circuit. The efficiency is further 6 increased with the low 70µA quiescent current and low on-resistance of the internal n-channel MOSFET power switch. The MAX1947 uses Maxim’s proprietary True Shutdown circuitry, which disconnects the output from the input in shutdown and actively discharges the output to ground. _______________________________________________________________________________________ Low Input/Output Voltage Step-Up DC-DC Converter with RESET BATT RESET 75ms TIMER STARTUP OSCILLATOR 0.9 x REF OUT SHDN SHUTDOWN CIRCUITRY ERROR AMPLIFIER REF P* tON MAX TIMER CONTROL LOGIC AND GATE DRIVERS tOFF MIN TIMER ZERO-CROSSING AMPLIFIER LX N REF CURRENT-LIMIT AMPLIFIER 1.25V REFERENCE (REF) PGND MAX1947 GND Control Scheme The MAX1947 is a bootstrapped design. Upon turn-on, a startup oscillator brings the output voltage high enough to allow the main DC-DC circuitry to run. Once the output voltage reaches 1.62V (typ) the main DC-DC circuitry turns on and boosts the output voltage to the final regulation point. The unique minimum off-time, current-limited control scheme is the key to the MAX1947’s low operating current and high efficiency over a wide load range. The architecture combines the high output power and efficiency of a pulse-width modulation (PWM) device with the ultra-low quiescent current of a traditional pulseskipping controller. The switching frequency can be as high as 2MHz and depends upon the load current and input voltage. The MAX1947 is designed to operate using low-ESR ceramic capacitors, so output voltage ripple due to ESR is very small (approximately 10mVP-P). Track Mode The MAX1947 enters track mode when BATT is greater than the output-voltage regulation point. Track mode can only be entered under the following conditions: *BODY DIODE CONTROL VBATT > VOUT, VOUT > VOUT regulation point, and the minimum off-time expires. During track mode, the synchronous rectifier is turned on 100% of the time and the output voltage tracks the battery voltage. Track mode is exited by VOUT falling below the VOUT regulation point. Synchronous Rectification The internal synchronous rectifier eliminates the need for an external Schottky diode, reducing cost and board space. During the cycle off-time, the p-channel MOSFET turns on and shunts the MOSFET body diode. As a result, the synchronous rectifier significantly improves efficiency without the addition of an external component. Conversion efficiency can be as high as 94%. RESET The MAX1947 features an active-low push-pull RESET output for use with a microcontroller (µC). It signals the µC when the MAX1947 output voltage is within operating limits. During startup, RESET is held low. When the RESET threshold (90% of the output regulation voltage) is reached, a 75ms (min) timer begins counting. RESET is switched high once the timer expires. _______________________________________________________________________________________ 7 MAX1947 Functional Diagram MAX1947 Low Input/Output Voltage Step-Up DC-DC Converter with RESET Table 1. Suggested Component Values APPLICATION LOAD INPUT CAPACITOR (µF) OUTPUT CAPACITOR (µF) INDUCTOR (µH) 1-Cell Input, Output < 2.7V ≤50% full load 2.2 4.7 3.3 1-Cell Input, Output > 2.7V 2-Cell Input >50% full load 2.2 10 3.3 ≤50% full load 2.2 4.7 4.7 >50% full load 2.2 10 4.7 ≤50% full load 2.2 4.7 6.8 >50% full load 2.2 10 6.8 Table 2. Suggested Component Manufacturers MANUFACTURER Sumida Taiyo Yuden TDK PART PART NUMBER PHONE Inductor CDRH3D16 series 81-3-3667-3381 www.sumida.com Output capacitors 4.7µF JMK212BJ475MG, 10µF JMK212BJ106MG 408-573-4150 www.t-yuden.com 888-835-6646 www.TDK.com Input capacitors 2.2µF LMK107BJ225MA Output capacitors 4.7µF C2012X5R0J475K, 10µF C2012X5R0J106K Input capacitors 2.2µF C1608X5R03225M Shutdown The MAX1947 enters shutdown mode when SHDN is driven low. During shutdown, the synchronous rectifier disconnects the output from the input, eliminating the DC conduction path that normally exists with traditional boost converters in shutdown mode. The output is actively discharged to ground through an internal 500Ω resistor. The quiescent current is reduced to 2µA while in shutdown mode. Drive SHDN high for normal operation. The output reaches regulation approximately 650µs after SHDN goes high. Applications Information Inductor Selection An inductor value of 4.7µH performs well in most applications. The MAX1947 also works with inductors in the 8 WEBSITE 2.2µH to 6.8µH range. Smaller inductance values typically offer a smaller physical size for a given series resistance, allowing the smallest overall circuit dimensions but with lower output-current capability. Circuits using larger inductance values exhibit higher outputcurrent capability, but are larger for the same series resistance and current rating. The inductor’s incremental saturation current rating should be greater than the peak switch-current limit. However, it is generally acceptable to bias the inductor into saturation by as much as 20%, although this slightly reduces efficiency (see the Electrical Characteristics for the MAX1947 NFET current limit). Table 1 lists the suggested components for several typical applications. Also, the inductor’s DC resistance significantly affects efficiency. _______________________________________________________________________________________ Low Input/Output Voltage Step-Up DC-DC Converter with RESET IRIPPLE = VOUT + ILIM × (RDS(ON)PFET + RL ) − VBATT L / t OFF + (RDS(ON)PFET + RL ) 2 IRIPPLE )× VOUT + (ILIM − 2 (RDS(ON)PFET + RL ) − VBATT D= I VOUT + (ILIM − RIPPLE ) × 2 R ( R − DS(ON)PFET DS(ON)NFET + RL ) Capacitor Selection The MAX1947 is specifically designed for using small, inexpensive, low-ESR ceramic capacitors. X5R and X7R dielectrics are recommended when operating over wide temperature ranges. Bypass the output of the MAX1947 with 10µF when using maximum load currents. When using less than half the maximum load current capability, the output capacitor can be reduced to 4.7µF. Bypass the input with a 2.2µF or larger ceramic capacitor. Table 1 lists the suggested values for the input and output capacitors for typical applications. PC Board Layout and Grounding I IOUTMAX = (ILIM − RIPPLE ) × (1− D) 2 Careful printed circuit-board layout is important for minimizing ground bounce and noise. Keep the IC’s GND pins and the ground leads of the input and output filter capacitors very close together. Connect GND and PGND directly to the exposed paddle. In addition, keep all connections to the OUT and LX pins as short as possible. To maximize output power and efficiency and minimize output ripple voltage, use short, wide traces from the input and output. A sample layout is available in the MAX1947 evaluation kit. Chip Information Here, ILIM is the NFET current limit (800mA typ), tOFF is the LX switch’s off-time (0.25µs typ), and R L is the series resistance of the inductor. TRANSISTOR COUNT: 5156 PROCESS: BiCMOS _______________________________________________________________________________________ 9 MAX1947 Calculate the maximum output current (IOUTMAX) using inductor ripple current (IRIPPLE) and duty cycle (D) as follows: Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 6, 8, &10L, DFN THIN.EPS MAX1947 Low Input/Output Voltage Step-Up DC-DC Converter with RESET D N PIN 1 INDEX AREA E E2 DETAIL A CL CL L A L e e PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm 21-0137 NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY F 1 2 COMMON DIMENSIONS SYMBOL A MIN. 0.70 0.80 D 2.90 3.10 E 2.90 3.10 0.00 0.05 A1 L k MAX. 0.40 0.20 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e T633-1 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF T833-1 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF T1433-1 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.03 2.40 REF T1433-2 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.03 2.40 REF PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm 21-0137 F 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.