19-1217; Rev 0; 4/97 Regulated 3.3V Charge Pump The MAX679’s switching frequency is pin selectable at 330kHz or 1MHz to allow trade-offs between lowest supply current and smallest-size capacitors. The logic shutdown function reduces the supply current to 5µA (max) and disconnects the load from the input. Special soft-start circuitry prevents excessive current from being drawn from the battery during start-up. This DCDC converter requires no inductors and has low EMI. It is available in the ultra-small µMAX package, which is only 1.11mm high and half the area of an 8-pin SO. ________________________Applications Battery-Powered Applications ____________________________Features ♦ Regulated 3.3V ±4% Output ♦ Ultra-Small: 1.1mm-High, 8-Pin µMAX Package ♦ No Inductors Required ♦ Up to 1MHz Operation (small external components) ♦ Fits into 0.05 in.2 ♦ Up to 85% Efficiency ♦ 1.8V to 3.6V Input Voltage Range ♦ 50µA Quiescent Supply Current ♦ 1µA Shutdown Current ______________Ordering Information PART MAX679C/D MAX679EUA Miniature Equipment Backup-Battery Boost Converters TEMP. RANGE 0°C to +70°C -40°C to +85°C PIN-PACKAGE Dice* 8 µMAX *Dice are tested at TA = +25°C only. Translators Two-Way Pagers __________Typical Operating Circuit INPUT 2V to 3.6V IN OUTPUT 3.3V, 20mA OUT __________________Pin Configuration TOP VIEW COUT CIN FSET 1 MAX679 8 OUT 7 C1+ IN 3 6 C1- GND 4 5 PGND SHDN 2 FSET MAX679 C1+ C1 SHDN OFF/ON C1PGND GND µMAX ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX679 _______________General Description The MAX679 step-up, regulated charge pump generates a 3.3V ±4% output voltage from a 1.8V to 3.6V input voltage (two alkaline, NiCd, or NiMH; or one Lithium-Ion battery). Output current is 20mA (min) from a 2.0V input. Only three external capacitors are needed to build a complete DC-DC converter. MAX679 Regulated 3.3V Charge Pump ABSOLUTE MAXIMUM RATINGS IN, OUT, SHDN, FSET to GND....................................-0.3V to 6V PGND to GND.....................................................................±0.3V C1- to GND ..................................................-0.3V to (VIN + 0.3V) C1+ to GND..............................................-0.3V to (VOUT + 0.3V) OUT Short to GND ..............................................................10sec Continuous Power Dissipation (TA = +70°C) µMAX (derate 4.1mW/°C above +70°C) .......................330mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C 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 (VIN = V S HDN = VFSET = 2V, CIN = 4.7µF, C1 = 0.33µF, COUT = 10µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) MAX UNITS Input Voltage PARAMETER 1.8 3.6 V Input Undervoltage Lockout Voltage 0.8 1.6 V Output Voltage CONDITIONS 2V < VIN < 3.3V, 0mA < IOUT < 20mA MIN TA = 0°C to +85°C 3.17 TA = -40°C to +85°C 3.15 TYP 3.3 3.43 V 3.45 Output Current VIN = 1.8V, VOUT > 3.17V 20 No-Load Supply Current VIN = 2.5V, FSET = IN or GND 50 80 µA Leakage Current into OUT in Shutdown VOUT = 3.6V, SHDN = GND 15 25 µA Supply Current in Shutdown VIN = 3.3V 1 5 µA FSET, SHDN Input Voltage Low VIN = 1.8V 0.5 x VIN 0.3 x VIN V FSET, SHDN Input Voltage High VIN = 3.6V FSET, SHDN Input Leakage Current FSET, SHDN = GND or VIN 0.7 x VIN mA 0.5 x VIN 0.1 V 1 FSET = GND 260 330 450 FSET = IN 700 1000 1300 200 Switching Frequency kHz Output Short-Circuit Current OUT = GND, VIN = 3.3V 100 Efficiency VIN = 2V, IOUT = 10mA 80 Note 1: Specifications to -40°C are guaranteed by design, not production tested. 2 µA _______________________________________________________________________________________ mA % Regulated 3.3V Charge Pump VIN = 2.4V 50 40 VIN = 3.0V VIN = 2.4V 50 VIN = 3.0V 40 VIN = 3.5V 1 2.8 0.1 10 1 20 30 40 50 60 70 SUPPLY CURRENT vs. SUPPLY VOLTAGE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE VIN = 2.0V 10 1 SHDN = GND DASHED LINES INDICATE OUTPUT OUT OF REGULATION 2.9 60 70 80 90 100 VIN = 2.4V 500 400 300 200 100 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 -40 -15 10 35 60 OUTPUT CURRENT (mA) SUPPLY VOLTAGE (V) TEMPERATURE (°C) PUMP FREQUENCY vs. TEMPERATURE PUMP FREQUENCY vs. TEMPERATURE OUTPUT RIPPLE (2mA LOAD) FSET = GND (330kHz) VIN = 2.5V 330 320 FSET = IN (1MHz) VIN = 2.5V 1080 1060 PUMP FREQUENCY (kHz) 340 MAX679 TOC08b 1100 MAX679 TOC08a 360 80 0 0.1 20 30 40 50 600 SHUTDOWN SUPPLY CURRENT (nA) VIN = 2.4V MAX679 TOC05 SHDN = IN SUPPLY CURRENT (µA) 3.2 VIN = 1.8V 100 MAX679 TOC02b VIN = 3.5V 3.0 PUMP FREQUENCY (kHz) 10 OUTPUT VOLTAGE vs. OUTPUT CURRENT VIN = 3.0V 350 0 100 OUTPUT CURRENT (mA) 3.3 10 DASHED LINES INDICATE OUTPUT OUT OF REGULATION OUTPUT CURRENT (mA) FSET = IN (1MHz) 0 VIN = 2.0V VIN = 1.8V OUTPUT CURRENT (mA) 3.4 3.1 VIN = 2.4V 3.1 2.9 0.01 100 10 3.2 FSET = GND (330kHz) 0 0 0.1 VIN = 3.0V 3.3 3.0 10 FSET = IN (1MHz) 0.01 VIN = 3.5V 3.4 20 20 OUTPUT VOLTAGE (V) 60 30 VIN = 3.5V 10 70 VIN = 2.0V FSET = GND (330kHz) 3.5 MAX679 TOC06 30 3.6 FSET = GND (330kHz) 85 MAX679 TOC09 60 EFFICIENCY (%) EFFICIENCY (%) 80 VIN = 2.0V 70 VIN = 1.8V OUTPUT VOLTAGE (V) 80 90 MAX679 TOC01b VIN = 1.8V 90 100 MAX679 TOC01a 100 OUTPUT VOLTAGE vs. OUTPUT CURRENT MAX679 TOC02a EFFICIENCY vs. OUTPUT CURRENT EFFICIENCY vs. OUTPUT CURRENT 1040 1020 VOUT 50mV/div AC COUPLED 1000 980 960 940 310 920 300 900 -40 -15 10 35 TEMPERATURE (°C) 60 MAX679 __________________________________________Typical Operating Characteristics (Typical Operating Circuit with: VIN = V S HDN = 2V, CIN = 4.7µF, C1 = 0.33µF, COUT = 10µF, tested in-circuit, TA = +25°C, unless otherwise noted.) 85 -40 -15 10 35 60 85 100µs/div TEMPERATURE (°C) _______________________________________________________________________________________ 3 MAX679 Regulated 3.3V Charge Pump ____________________________Typical Operating Characteristics (continued) (Typical Operating Circuit with: VIN = V S HDN = 2V, CIN = 4.7µF, C1 = 0.33µF, COUT = 10µF, tested in-circuit, TA = +25°C, unless otherwise noted.) LOAD-TRANSIENT RESPONSE (1mA TO 10mA LOAD, VIN = 2V) LOAD-TRANSIENT RESPONSE (1mA TO 10mA LOAD, VIN = 3V) OUTPUT RIPPLE (2mA LOAD) MAX679 TOC12 MAX679 TOC11 MAX679 TOC10 FSET = IN (1MHz) VOUT 10mV/div AC COUPLED VOUT 10mV/div AC COUPLED IOUT 5mA/div IOUT 5mA/div VOUT 50mV/div AC COUPLED VIN = 2V FSET = IN (1MHz) VIN = 3V FSET = IN (1MHz) 100µs/div 50µs/div 100µs/div ______________________________________________________________Pin Description PIN NAME FUNCTION 1 FSET Set Charge-Pump Frequency Input. FSET = GND selects 330kHz and FSET = IN selects 1MHz. Do not leave FSET unconnected. 2 SHDN 3 IN Shutdown Input. The device shuts down, the output disconnects from the input, and the supply current decreases to 1µA when SHDN is a logic low. Connect SHDN to IN for normal operation. Supply Input. Connect to an input supply in the 1.8V to 3.6V range. Bypass IN to GND with a (COUT / 2)µF capacitor. 4 GND 5 PGND Ground. Analog ground for internal reference and control circuitry. 6 C1- Negative Terminal of the Charge-Pump Capacitor 7 C1+ Positive Terminal of the Charge-Pump Capacitor 8 OUT 3.3V Power Output. Bypass OUT to GND with an output filter capacitor (see the Design Procedure section). Power Ground. Charge-pump current flows through this pin. _______________Detailed Description The MAX679 regulated charge pump has a 50% dutycycle clock. In phase one (charge phase), the chargetransfer capacitor (C1) charges to the input voltage, and output current is delivered by the output filter capacitor (COUT). In phase two (transfer phase), C1 is placed in series with the input and connects to the output, transferring its charge to COUT. If the clock were to run continuously, this process would eventually generate an output voltage equal to two times the input voltage (hence the name “doubler”). 4 The charge pump regulates by gating the oscillator on and off as needed to maintain output regulation. This method has low quiescent current, but to achieve acceptable output ripple, C1 must be significantly lower in value than COUT. Start-Up Sequence The MAX679 soft-start circuitry prevents excessive current from being drawn from the battery at start-up or when the output is shorted. This is done by limiting the charge pump to 1/10 the normal current until either the output is in regulation or the first 4096 charge-pump _______________________________________________________________________________________ Regulated 3.3V Charge Pump MAX679 IN OUT CHIP SUPPLY P5 ΦSW P6 ΦT P4 C1+ P3 MAX679 C1 ΦC P2 ΦT SHDN C1- PULSER P1 ΦSW N1 ΦC ΦC OSCILLATOR + CONTROL LOGIC PGND ΦT ΦSC CLOCK ΦSC 10% OF N1 RESET FSET 212 COUNTER OUT EAOUT (1 = OUTPUT OVER REGULATION POINT) 1.25V REF ΦSW = ΦT = ΦC = ΦSC = GND SWITCH CONNECTS OUT TO IN DURING START-UP TRANSFER PHASE OF PUMP CHARGE PHASE OF PUMP (FULL STRENGTH) CHARGE PHASE OF PUMP (REDUCED STRENGTH) Figure 1. Block Diagram _______________________________________________________________________________________ 5 MAX679 Regulated 3.3V Charge Pump cycles (about 4ms) have elapsed. The start-up sequence begins at power-up, when exiting shutdown, or when recovering from a short circuit. If VIN is less than the 1.6V UVLO threshold, the device remains shut down and ignores a high SHDN input. Table 1. External Component Selection __________________Design Procedure Optimize the charge-pump circuit for size, quiescent current, and output ripple by properly selecting the operating frequency and capacitors C IN , C1, and COUT. For lowest output ripple, select 1MHz operation (FSET = IN). In addition, increasing COUT relative to C1 will further reduce ripple. For highest efficiency, select 330kHz operation (FSET = GND) and select the largest practical values for COUT and C1 while maintaining a 30-to-1 ratio. See Table 1 for some suggested values and the resulting output ripple. Note that the capacitors must have low ESR (<20mΩ) to maintain low ripple. Currently, only ceramic capacitors can provide such low ESR; therefore, the output filter capacitors should be a combination of a 1µF ceramic capacitor and a 10µF tantalum capacitor. Smallest Size Set the frequency to 1MHz by connecting FSET to IN. Table 1 shows typical external component values. VIN (V) C1 (µF) COUT (µF) FSET (Hz) Vp-p (mV) 2 0.33 10 1M 7 2 0.33 10 330k 14 2 0.1 3.3 1M 16 2 0.1 3.3 330k 22 3 0.33 10 1M 27 3 0.33 10 330k 56 3 0.1 3.3 1M 72 3 0.1 3.3 330k 89 PC Board Layout Place C1, C OUT , and C IN close to the IC. Connect PGND and GND with a short trace. Efficiency Charge-pump efficiency is best at low frequency (330kHz). The theoretical maximum efficiency is given in the following equation: Theoretical maximum efficiency = VOUT / (2 x VIN) Gate-charge losses amount to approximately 1mA from the output at full switching frequency (about 5% to 7% loss). Table 2. Manufacturers of Low-ESR Capacitors PRODUCTION METHOD MANUFACTURER Surface-Mount Tantalum Capacitors Surface-Mount Ceramic Capacitors CAPACITORS PHONE FAX AVX TPS series (803) 946-0690 (803) 626-3123 Matsuo 267 series (714) 969-2491 (714) 960-6492 Sprague 593D, 595D series (603) 224-1961 (603) 224-1430 AVX X7R (803) 946-0690 (803) 626-3123 Matsuo X7R (714) 969-2491 (714) 960-6492 ___________________Chip Information TRANSISTOR COUNT: 819 SUBSTRATE CONNECTED TO GND 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. 6 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.