19-1217; Rev ; 4/97 Regulated 3.3 Charge Pump General Description The step-up, regulated charge pump generates a 3.3 ±4% output voltage from a 1.8 to 3.6 input voltage (two alkaline, NiCd, or NiMH; or one Lithium-Ion battery). Output current is 2mA (min) from a 2. input. Only three external capacitors are needed to build a complete DC-DC converter. The s switching frequency is pin selectable at 33kHz or 1MHz to allow trade-offs between lowest supply current and smallest-size capacitors. The logic shutdown function reduces the supply current to 5 (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 DC- DC 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. Features Regulated 3.3 ±4% Output Ultra-Small: 1.1mm-High, 8-Pin µmax Package No Inductors Required Up to 1MHz Operation (small external components) Fits into.5 in. 2 Up to 85% Efficiency 1.8 to 3.6 Input oltage Range 5 Quiescent Supply Current 1 Shutdown Current Applications Battery-Powered Applications Miniature Equipment Backup-Battery Boost Converters Translators Two-Way Pagers Ordering Information PART TEMP. RANGE PIN-PACKAGE C/D C to +7 C Dice* EUA -4 C to +85 C 8 µmax *Dice are tested at T A = +25 C only. Typical Operating Circuit Pin Configuration INPUT 2 to 3.6 IN PUT 3.3, 2mA TOP IEW C IN C 1 8 OFF/ON SHDN PGND GND C1+ C1+ C1- PGND C1- C1 SHDN IN GND 2 3 4 µmax 7 6 5 Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-8-998-88
ABSOLUTE MAXIMUM RATINGS IN,, SHDN, to GND...-.3 to 6 PGND to GND...±.3 C1- to GND...-.3 to ( IN +.3) C1+ to GND...-.3 to ( +.3) Short to GND...1sec Continuous Power Dissipation (T A = +7 C) µmax (derate 4.1mW/ C above +7 C)...33mW Operating Temperature Range...-4 C to +85 C Storage Temperature Range...-65 C to +16 C Lead Temperature (soldering, 1sec)...+3 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 ( IN = SHDN = = 2, C IN = 4.7µF, C1 =.33µF, C = 1µF, T A = -4 C to +85 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) Input oltage Input Undervoltage Lockout oltage Output oltage Output Current PARAMETER No-Load Supply Current Leakage Current into in Shutdown Supply Current in Shutdown, SHDN Input oltage Low, > 3.17 IN = 2.5, = IN or GND = 3.6, SHDN = GND IN = 3.3 CONDITIONS MIN TYP MAX 1.8 3.6.8 1.6 2 < IN < 3.3, T A = C to +85 C 3.17 3.3 3.43 ma < I < 2mA T A = -4 C to +85 C 3.15 3.45 2 5 8 15 25 1 5.5 x.3 x IN IN UNITS ma, SHDN Input oltage High IN = 3.6.7 x.5 x IN IN, SHDN Input Leakage Current, SHDN = GND or IN.1 1 Switching Frequency = GND = IN 26 33 45 7 1 13 khz Output Short-Circuit Current = GND, IN = 3.3 1 2 ma Efficiency IN = 2, I = 1mA 8 % Note 1: Specifications to -4 C are guaranteed by design, not production tested. 2
Typical Operating Characteristics (Typical Operating Circuit with: IN = SHDN = 2, C IN = 4.7µF, C1 =.33µF, C = 1µF, tested in-circuit, T A = +25 C, unless otherwise noted.) EFFICIENCY (%) 1 9 8 7 6 5 4 3 2 1 EFFICIENCY IN = 2. IN = 2.4 IN = 3. IN = 3.5.1.1 1 1 1 TOC1a EFFICIENCY (%) 1 9 8 7 6 5 4 3 2 1.1 EFFICIENCY IN = 2. IN = 3..1 1 1 1 IN = 2.4 IN = 3.5 = GND (33kHz) TOC1b PUT OLTAGE () 3.6 3.5 3.4 3.3 3.2 3.1 3. 2.9 2.8 PUT OLTAGE = GND (33kHz) DASHED LINES INDICATE PUT OF REGULATION IN = 3.5 IN = 3. IN = 2. IN = 2.4 1 2 3 4 5 6 7 8 TOC2a PUT OLTAGE () 3.4 3.3 3.2 3.1 3. 2.9 PUT OLTAGE IN = 2. DASHED LINES INDICATE PUT OF REGULATION IN = 3.5 IN = 3. IN = 2.4 1 2 3 4 5 6 7 8 9 1 TOC2b SUPPLY CURRENT () 1 1 1.1 1.8 SHDN = IN SHDN = GND SUPPLY CURRENT vs. SUPPLY OLTAGE 2. 2.2 2.4 2.6 2.8 3. 3.2 3.4 3.6 SUPPLY OLTAGE () TOC5 SHUTDOWN SUPPLY CURRENT (na) 6 5 4 3 2 1-4 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE IN = 2.4-15 1 35 6 85 TEMPERATURE ( C) TOC6 36 35 PUMP FREQUENCY vs. TEMPERATURE = GND (33kHz) IN = 2.5 TOC8a 11 18 16 IN = 2.5 PUMP FREQUENCY vs. TEMPERATURE TOC8b PUT RIPPLE (2mA LOAD) = GND (33kHz) TOC9 PUMP FREQUENCY (khz) 34 33 32 PUMP FREQUENCY (khz) 14 12 1 98 96 5m/div 31 94 92 3-4 -15 1 35 6 85 TEMPERATURE ( C) 9-4 -15 1 35 6 85 TEMPERATURE ( C) 1µs/div 3
Typical Operating Characteristics (continued) (Typical Operating Circuit with: IN = SHDN = 2, C IN = 4.7µF, C1 =.33µF, C = 1µF, tested in-circuit, T A = +25 C, unless otherwise noted.) PUT RIPPLE (2mA LOAD) TOC1 LOAD-TRANSIENT RESPONSE (1mA TO 1mA LOAD, IN = 3) TOC11 LOAD-TRANSIENT RESPONSE (1mA TO 1mA LOAD, IN = 2) TOC12 1m/div 1m/div 5m/div I 5mA/div I 5mA/div 1µs/div IN = 3 1µs/div IN = 2 5µs/div Pin Description PIN NAME FUNCTION 1 2 SHDN 3 IN Set Charge-Pump Frequency Input. = GND selects 33kHz and = IN selects 1MHz. Do not leave unconnected. Shutdown Input. The device shuts down, the output disconnects from the input, and the supply current decreases to 1 when SHDN is a logic low. Connect SHDN to IN for normal operation. Supply Input. Connect to an input supply in the 1.8 to 3.6 range. Bypass IN to GND with a (C / 2)µF capacitor. 4 GND Ground. Analog ground for internal reference and control circuitry. 5 PGND Power Ground. Charge-pump current flows through this pin. 6 C1- Negative Terminal of the Charge-Pump Capacitor 7 C1+ Positive Terminal of the Charge-Pump Capacitor 8 3.3 Power Output. Bypass to GND with an output filter capacitor (see the Design Procedure section). Detailed Description The regulated charge pump has a 5% 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 (C). In phase two (transfer phase), C1 is placed in series with the input and connects to the output, transferring its charge to C. 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 ). 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 C. Start-Up Sequence The 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 1/1 the normal current until either the output is in regulation or the first 496 charge-pump 4
CHIP SUPPLY IN P6 P5 P4 Φ SW Φ T P3 C1+ Φ C C1 P2 Φ T SHDN PULSER C1- Φ SW P1 Φ C N1 OSCILLATOR + CONTROL LOGIC Φ C Φ T Φ SC Φ SC PGND CLOCK 1% OF N1 RESET 2 12 COUNTER EA (1 = PUT OER REGULATION POINT) 1.25 REF GND Φ SW = SWITCH CONNECTS TO IN DURING START-UP Φ T = TRANSFER PHASE OF PUMP Φ C = CHARGE PHASE OF PUMP (FULL STRENGTH) Φ SC = CHARGE PHASE OF PUMP (REDUCED STRENGTH) Figure 1. Block Diagram 5
cycles (about 4ms) have elapsed. The start-up sequence begins at power-up, when exiting shutdown, or when recovering from a short circuit. If IN is less than the 1.6 ULO threshold, the device remains shut down and ignores a high SHDN input. 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 C. For lowest output ripple, select 1MHz operation ( = IN). In addition, increasing C relative to C1 will further reduce ripple. For highest efficiency, select 33kHz operation ( = GND) and select the largest practical values for C and C1 while maintaining a 3-to-1 ratio. See Table 1 for some suggested values and the resulting output ripple. Note that the capacitors must have low ESR (<2mΩ) 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 1µF tantalum capacitor. Smallest Size Set the frequency to 1MHz by connecting to IN. Table 1 shows typical external component values. Table 1. External Component Selection IN () C1 (µf) C (µf) 2 2.33.33 1 1 2.1 3.3 2.1 3.3 3.33 1 3.33 1 3.1 3.3 3.1 3.3 (Hz) p-p (m) 1M 33k 7 14 1M 16 33k 22 1M 27 33k 56 1M 72 33k 89 PC Board Layout Place C1, C, and CIN close to the IC. Connect PGND and GND with a short trace. Efficiency Charge-pump efficiency is best at low frequency (33kHz). The theoretical maximum efficiency is given in the following equation: Theoretical maximum efficiency = / (2 x IN) 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 CAPACITORS PHONE FAX Surface-Mount Tantalum Capacitors Surface-Mount Ceramic Capacitors AX Matsuo Sprague AX Matsuo TPS series 267 series 593D, 595D series X7R (83) 946-69 (83) 626-3123 (714) 969-2491 (63) 224-1961 (63) 224-143 (83) 946-69 (714) 96-6492 (83) 626-3123 X7R (714) 969-2491 (714) 96-6492 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, 12 San Gabriel Drive, Sunnyvale, CA 9486 (48) 737-76 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.