50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters

Transcription

1 9-39; Rev ; /3 General escription The charge-pump voltage converters invert input voltages ranging from +.5V to +5.5V, or double input voltages ranging from +.5V to +5.5V. Because of their high switching frequencies, these devices use only two small, low-cost capacitors. Their 5mA output makes switching regulators unnecessary, eliminating inductors and their associated cost, size, and EMI. Greater than 9% efficiency over most of the load-current range, combined with a typical operating current of only µa (MAX6), provides ideal performance for both battery-powered and board-level voltage-conversion applications. A frequency-control (FC) pin provides three switchingfrequencies to optimize capacitor size and quiescent current and to prevent interference with sensitive circuitry. Each device has a unique set of three available frequencies. A shutdown (S H N ) pin reduces current consumption to less than µa. The are suitable for use in applications where the ICL66 and MAX66's switching frequencies are too low. The are available in -pin µmax and SO packages. Applications Portable Computers Medical Instruments Interface Power Supplies Hand-Held Instruments Operational-Amplifier Power Supplies Typical Operating Circuit Features -Pin,.mm High µmax Package Invert or ouble the Input Supply Voltage Three Selectable Switching Frequencies High Frequency Reduces Capacitor Size % Efficiency at 5mA µa Quiescent Current (MAX6) µa Shutdown Supply Current 6mV Voltage rop at 5mA Load Ω Output Resistance Ordering Information PART MAX6ISA MAX6IUA TEMP RANGE -5 C to +5 C -5 C to +5 C MAX6C/ C to + C ice* PIN-PACKAGE SO µmax MAX6ESA - C to +5 C SO MAX6MJA -55 C to +5 C CERIP MAX6ISA -5 C to +5 C SO MAX6IUA -5 C to +5 C µmax MAX6C/ C to + C ice* MAX6ESA - C to +5 C SO MAX6MJA -55 C to +5 C CERIP *ice are tested at T A = +5 C, C parameters only. Contact factory for availability. C FC MAX6 V MAX6 C+ SHN µf 3 GN C- LV OUT 6 5 VOLTAGE INVERTER INPUT VOLTAGE +.5V TO +5.5V INVERTE NEGATIVE OUTPUT µf C Pin Configuration TOP VIEW INPUT VOLTAGE +.5V TO +5.5V C µf 3 FC MAX6 V MAX6 C+ SHN GN LV C- OUT 6 5 OUBLE POSITIVE OUTPUT µf C FC C+ GN C- 3 MAX6 MAX6 SO/µMAX 6 5 V SHN LV OUT POSITIVE VOLTAGE OUBLER Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/allas irect! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS Supply Voltage (V to GN or GN to OUT)...+6.V Input Voltage Range (LV, FC, S H N )...(OUT -.3V) to (V +.3V) Continuous Output Current (OUT, V )...6mA Output Short-Circuit to GN (Note )...s Continuous Power issipation (T A = + C) SO (derate 5.mW/ C above + C)...mW µmax (derate.mw/ C above + C)...33mW CERIP (derate.mw/ C above + C)...6mW Note : Operating Temperature Ranges MAX6_I_A...-5 C to +5 C MAX6_ESA...- C to +5 C MAX6_MJA C to +5 C Storage Temperature Range C to +6 C Lead Temperature (soldering, s)...+3 C OUT may be shorted to GN for sec without damage, but shorting OUT to V may damage the device and should be avoided. Also, for temperatures above +5 C, OUT must not be shorted to GN or V, even instantaneously, or device damage may result. 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 (Typical Operating Circuit (Inverter), V = +5V, S H N = V, FC = LV = GN, C = C = µf (Note ), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONITIONS MIN TYP MAX UNITS Supply Voltage V R L = kω Inverter, LV = GN oubler, LV = OUT V = 5V..3 MAX6I/E = 3V No-Load Supply Current (Note 3) I MAX6M ma MAX6I/E MAX6M V = 5V, V OUT more negative than -3.5V 5 Output Current I OUT ma V = 3V, V OUT more negative than -.5V 3 Output Resistance (Note ) R OUT I L = 5mA I L = ma, V = V 5 35 Ω

3 ELECTRICAL CHARACTERISTICS (continued) (Typical Operating Circuit (Inverter), V = +5V, S H N = V, FC = LV = GN, C = C = µf (Note ), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER Switching Frequency (Note 5) FC Current (from V ) SYMBOL f S I FC MAX6 MAX6 FC < V MAX6, CONITIONS R L = kω from V to OUT R L = kω from OUT to GN MIN TYP MAX UNITS khz µa Power Efficiency (Note 6) MAX6, R L = kω from V to OUT R L = kω from OUT to GN %,, I L = 5mA to GN, C = C = 6µF Voltage-Conversion Efficiency No load % S H N Threshold Shutdown Supply Current Time to Exit Shutdown V IH V IL LV = GN..3 V S H N <.3V MAX6_I/E MAX6_M µa No load, V OUT = -V 5 µs Note : Note 3: Note : Note 5: Note 6: C and C are low-esr (<.Ω) aluminum electrolytics. Capacitor ESR adds to the circuit s output resistance. Using capacitors with higher ESR may reduce output voltage and efficiency. may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee proper startup, the input supply must be capable of delivering 9mA more than the maximum load current. Specified output resistance includes the effect of the.ω ESR of the test circuit s capacitors. The switches are driven directly at the oscillator frequency, without any division. At lowest frequencies, using µf capacitors gives worse efficiency figures than using the recommended capacitor values in Table 3, due to larger (f s x C) term in R OUT. 3

4 Typical Operating Characteristics (All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GN and T A = +5 C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and T A = +5 C. All capacitor values used are those recommended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is R O in the equation for R OUT shown in the Capacitor Selection section.) VOUT ROP (V) OUTPUT SOURCE RESISTANCE (Ω) OUTPUT VOLTAGE ROP FROM SUPPLY VOLTAGE vs. LOA CURRENT ALL FREQUENCIES V = +.5V V = +.5V V = +3.5V V = +.5V, +5.V V = +5.5V 3 5 LOA CURRENT (ma) OUTPUT SOURCE RESISTANCE (R O ) vs. TEMPERATURE ALL FREQUENCIES V = +3V TEMPERATURE ( C) V = +.5V V = +5V MAX6- MAX6- PERCENTAGE FREQUENCY CHANGE (%) (FROM FREQUENCY MEASURE WITH V = +5V) EFFICIENCY (%) OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE - ALL FREQUENCIES, LV CONNECTE TO GN - (INVERTER) OR OUT (OUBLER) SUPPLY VOLTAGE (V) MAX6 EFFICIENCY vs. LOA CURRENT V = +.5V V = +3V V = +5V INVERTER.. LOA CURRENT (ma) MAX6- MAX6-5 OUTPUT SOURCE RESISTANCE (Ω) SUPPLY CURRENT (µa) OUTPUT SOURCE RESISTANCE (R O ) vs. SUPPLY VOLTAGE ALL FREQUENCIES 3 5 SUPPLY VOLTAGE (V) MAX6 SUPPLY CURRENT vs. SUPPLY VOLTAGE OUBLER, LV = OUT INVERTER, LV = GN (V > 3V) SUPPLY VOLTAGE (V) MAX6-3 MAX6-6 SUPPLY CURRENT (µa) 5 3 MAX6 SUPPLY CURRENT vs. SUPPLY VOLTAGE OUBLER, LV = OUT INVERTER, LV = GN MAX6- OUTPUT CURRENT (ma) MAX6 OUTPUT CURRENT vs. CAPACITANCE HIGH-FREQUENCY MOE f OSC = 3kHz 6 LV = GN INVERTER MOE 5 V IN = +.5V, V OUT = -3.5V V IN = +.5V, V OUT = -V 3 V IN = +3V, V OUT = -.V V IN = +3V, V OUT = -.V MAX6- OUTPUT CURRENT (ma) MAX6 OUTPUT CURRENT vs. CAPACITANCE MEIUM-FREQUENCY MOE f OSC = 5kHz LV = GN 6 INVERTER MOE V IN = +.5V, V OUT = -3.5V 5 3 V IN = +3V, V OUT = -.V V IN = +.5V, V OUT = -V V IN = +3V, V OUT = -.V MAX SUPPLY VOLTAGE (V).33.. CAPACITANCE (µf).33.. CAPACITANCE (µf)

5 Typical Operating Characteristics (continued) (All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GN and T A = +5 C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and T A = +5 C. All capacitor values used are those recommended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is R O in the equation for R OUT shown in the Capacitor Selection section.) OUTPUT CURRENT (ma) MAX6 OUTPUT CURRENT vs. CAPACITANCE HIGH-FREQUENCY MOE f OSC = 5kHz LV = GN INVERTER MOE V IN = +.5V, V OUT = -V V IN = +.5V, V OUT = -3.5V V IN = +3V, V OUT = -.V V IN = +3V, V OUT = -.V MAX6- OUTPUT CURRENT (ma) MAX6 OUTPUT CURRENT vs. CAPACITANCE MEIUM-FREQUENCY MOE f OSC = khz LV = GN INVERTER MOE V IN = +3V, V OUT = -.V V IN = +.5V, V OUT = -3.5V V IN = +.5V, V OUT = -V V IN = +3V, V OUT = -.V MAX CAPACITANCE (µf).33.. CAPACITANCE (µf) Pin escription PIN NAME INVERTER FUNCTION OUBLER FC Frequency Control, see Table Frequency Control, see Table C+ Flying-Capacitor Positive Terminal Flying-Capacitor Positive Terminal 3 GN Ground Positive Input Supply C- Flying-Capacitor Negative Terminal Flying-Capacitor Negative Terminal 5 OUT Negative Output Ground 6 LV Low-Voltage-Operation Input. Connect to GN. Low-Voltage-Operation Input. Connect to OUT. S H N Active-Low Shutdown Input. Connect to V if not used. Connect to GN to disable the charge pump. Active-Low Shutdown Input. Connect to GN pin if not used. Connect to OUT to disable the charge pump. V Positive Input Supply oubled Positive Output 5

6 etailed escription The capacitive charge pumps either invert or double the voltage applied to their inputs. For highest performance, use low equivalent series resistance (ESR) capacitors. See the Capacitor Selection section for more details. The frequency-control (FC) pin allows you to choose one of three switching frequencies; these three selectable frequencies are different for each device. When shut down, current consumption reduces to less than µa. Common Applications Voltage Inverter The most common application for these devices is a charge-pump voltage inverter (see Typical Operating Circuits). This application requires only two external components capacitors C and C plus a bypass capacitor if necessary (see Bypass Capacitor section). Refer to the Capacitor Selection section for suggested capacitor types and values. Even though the s output is not actively regulated, it is fairly insensitive to load-current changes. A circuit output source resistance of Ω (calculated using the formula given in the Capacitor Selection section) means that, with a +5V input, the output voltage is -5V under no load and decreases to -.V with a 5mA load. The output source resistance (used to calculate the circuit output source resistance) vs. temperature and supply voltage are shown in the Typical Operating Characteristics graphs. Calculate the output ripple voltage using the formula given in the Capacitor Selection section. Positive Voltage oubler The can also operate as positive voltage doublers (see Typical Operating Circuits). This application requires only two external components, capacitors C and C. The no-load output is twice the input voltage. The electrical specifications in the doubler mode are very similar to those of the inverter mode except for the Supply Voltage Range (see Electrical Characteristics table) and No-Load Supply Current (see graph in Typical Operating Characteristics). The circuit output source resistance and output ripple voltage are calculated using the formulas in the Capacitor Selection section. Active-Low Shutdown Input When driven low, the S H N input shuts down the device. In inverter mode, connect S H N to V if it is not used. In doubler mode, connect S H N to GN if it is not used. When the device is shut down, all active circuitry is turned off. In the inverting configuration, loads connected from OUT to GN are not powered in shutdown mode. However, a reverse-current path exists through two diodes between OUT and GN; therefore, loads connected from V to OUT draw current from the input supply. In the doubling configuration, loads connected from the V pin to the GN pin are not powered in shutdown mode. Loads connected from the V pin to the OUT pin draw current from the input supply through a path similar to that of the inverting configuration (described above). Frequency Control Charge-pump frequency for both devices can be set to one of three values. Each device has a unique set of three available frequencies, as indicated in Table. The oscillator and charge-pump frequencies are the same (i.e., the charge-pump frequency is not half the oscillator frequency, as it is on the MAX66, MAX665, and ICL66). Table. Nominal Switching Frequencies* FC CONNECTION FREQUENCY (khz) MAX6 *See the Electrical Characteristics for detailed switchingfrequency specifications. MAX6 or open A higher switching frequency minimizes capacitor size for the same performance and increases the supply current (Table ). The lowest fundamental frequency of the switching noise is equal to the minimum specified switching frequency (e.g., 3kHz for the MAX6 with FC open). The spectrum of noise frequencies extends above this value because of harmonics in the switching waveform. To get best noise performance, choose the device and FC connection to select a minimum switching frequency that lies above your sensitive bandwidth. Low-Voltage-Operation Input LV should be connected to GN for inverting operation. To enhance compatibility with the MAX66, MAX665, and ICL66, you may float LV if the input voltage exceeds 3V. In doubling mode, LV must be connected to OUT for all input voltages. 6

7 Table. Switching-Frequency Trade-Offs ATTRIBUTE LOWER FREQUENCY HIGHER FREQUENCY Output Ripple Larger Smaller C, C Values Larger Smaller Supply Current Smaller Larger Applications Information Capacitor Selection The are tested using µf capacitors for both C and C, although smaller or larger values can be used (Table 3). Smaller C values increase the output resistance; larger values reduce the output resistance. Above a certain point, increasing the capacitance of C has a negligible effect (because the output resistance becomes dominated by the internal switch resistance and the capacitor ESR). Low-ESR capacitors provide the lowest output resistance and ripple voltage. The output resistance of the entire circuit (inverter or doubler) is approximately: ROUT = RO + x ESRC + ESRC + / (fs x C) where RO (the effective resistance of the MAX6/ MAX6 s internal switches) is approximately Ω and f S is the switching frequency. R OUT is typically Ω when using capacitors with.ω ESR and fs, C, and C values suggested in Table 3. When C and C are so large (or the switching frequency is so high) that the internal switch resistance dominates the output resistance, estimate the output resistance as follows: R OUT = R O + x ESR C + ESR C A typical design procedure is as follows: ) Choose C and C to be the same, for convenience. ) Select f S : a) If you want to avoid a specific noise frequency, choose f S appropriately. b) If you want to minimize capacitor cost and size, choose a high fs. c) If you want to minimize current consumption, choose a low fs. 3) Choose a capacitor based on Table 3, although higher or lower values can be used to optimize performance. Table lists manufacturers who provide low-esr capacitors. Table 3. Suggested Capacitor Values* NOMINAL FREQUENCY (khz) C, C (µf) *In addition to Table 3, four graphs in the Typical Operating Characteristics section show typical output current for C and C capacitances ranging from.33µf to µf. Output current is plotted for inputs of.5v (5V - %) and 3.V (3.3V - %), and also for % and % output droop from the ideal -V IN value. Table. Low-ESR Capacitor Manufacturers MANUFACTURER Series PHONE FAX COMMENTS AVX TPS Series (3) (3) Low-ESR tantalum, SMT AVX TAG Series (3) (3) Low-cost tantalum, SMT Matsuo 6 Series () () Low-cost tantalum, SMT Sprague 595 Series (63) -96 (63) -3 Low-ESR tantalum, SMT Sanyo MV-GX Series (69) (69) Aluminum electrolytic, through hole Sanyo CV-GX Series (69) (69) Aluminum electrolytic, SMT Nichicon PL Series () 3-5 () 3-9 Aluminum electrolytic, through hole United Chemicon (Marcon) () 696- () Ceramic SMT TK () 39-6 () 39-5 Ceramic SMT

8 Flying Capacitor, C Increasing the size of the flying capacitor reduces the output resistance. Output Capacitor, C Increasing the size of the output capacitor reduces the output ripple voltage. ecreasing its ESR reduces both output resistance and ripple. Smaller capacitance values can be used if one of the higher switching frequencies is selected, if less than the maximum rated output current (5mA) is required, or if higher ripple can be tolerated. The following equation for peak-to-peak ripple applies to both the inverter and doubler circuits. I OUT VRIPPLE = + x IOUT x ESRC x f S x C Bypass Capacitor Bypass the incoming supply to reduce its AC impedance and the impact of the s switching noise. The recommended bypassing depends on the circuit configuration and where the load is connected. When the inverter is loaded from OUT to GN or the doubler is loaded from V to GN, current from the supply switches between x IOUT and zero. Therefore, use a large bypass capacitor (e.g., equal to the value of C) if the supply has a high AC impedance. When the inverter and doubler are loaded from V to OUT, the circuit draws x IOUT constantly, except for short switching spikes. A.µF bypass capacitor is sufficient. Cascading evices Two devices can be cascaded to produce an even larger negative voltage, as shown in Figure. The unloaded output voltage is nominally - x V IN, but this is reduced slightly by the output resistance of the first device multiplied by the quiescent current of the second. The output resistance of the complete circuit is approximately five times the output resistance of a single. Three or more devices can be cascaded in this way, but output resistance rises dramatically, and a better solution is offered by inductive switching regulators (such as the MAX55, MAX59, MAX6, or MAX). Connect LV as with a standard inverter circuit (see Pin escription). The maximum load current and startup current of nth cascaded circuit must not exceed the maximum output current capability of (n-)th circuit to ensure proper startup. Paralleling evices Paralleling multiple MAX6s or MAX6s reduces the output resistance. As illustrated in Figure, each device requires its own pump capacitor (C), but the reservoir capacitor (C) serves all devices. C s value should be increased by a factor of n, where n is the number of devices. Figure shows the equation for calculating output resistance. An alternative solution is to use the MAX66 or MAX665, which are capable of supplying up to ma of load current. Connect LV as with a standard inverter circuit (see Pin escription). Combined oubler/inverter In the circuit of Figure 3, capacitors C and C form the inverter, while C3 and C form the doubler. C and C3 are the pump capacitors; C and C are the reservoir capacitors. Because both the inverter and doubler use part of the charge-pump circuit, loading either output causes both outputs to decline towards GN. Make C +V IN 3 MAX6 C 3 MAX6 5 C MAX6 MAX6 n 5 V OUT C C +V IN 3 MAX6 C 3 MAX6 5 R OUT = R OUT OF SINGLE EVICE NUMBER OF EVICES MAX6 MAX6 n 5 V OUT V OUT = -nv IN V OUT = -V IN C Figure. Cascading MAX6s or MAX6s to Increase Output Voltage Figure. Paralleling MAX6s or MAX6s to Reduce Output Resistance

9 C +V IN, = N 3 MAX6 MAX6 5 V OUT = -V IN Figure 3. Combined oubler and Inverter C3 C C V OUT = (V IN ) - (V F ) - (V F ) Table 5. Product Selection Guide PART NUMBER OUTPUT CURRENT (ma) OUTPUT RESISTANCE (Ω) SWITCHING FREQUENCY (khz) MAX / MAX / MAX6 5 6/5/3 MAX6 5 3//5 ICL sure the sum of the currents drawn from the two outputs does not exceed 6mA. Connect LV as with a standard inverter circuit (see Pin escription). Chip Topography Compatibility with MAX66/MAX665/ICL66 The can be used in sockets designed for the MAX66, MAX665, and ICL66 with a minimum of one wiring change. This section gives advice on installing a into a socket designed for one of the earlier devices. The MAX66, MAX665, and ICL66 have an OSC pin instead of S H N. MAX66, MAX665, and ICL66 normal operation is with OSC floating (although OSC can be overdriven). If OSC is floating, pin ( S H N ) should be jumpered to V to enable the permanently. o not leave S H N on the MAX6/ MAX6 floating. The operate with FC either floating or connected to V, OUT, or GN; each connection defines the oscillator frequency. Thus, any of the normal MAX66, MAX665, or ICL66 connections to pin will work with the, without modifications. Changes to the FC connection are only required if you want to adjust the operating frequency. FC C+ GN C-.5" (.mm) TRANSISTOR COUNT: SUBSTRATE CONNECTE TO V V SHN LV." (.3mm) OUT 9

10 PROPRIETARY INFORMATION TITLE: APPROVAL 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 CIPS.EPS IM MIN INCHES MAX MILLIMETERS MIN MAX SOICN.EPS A N A....5 B C e.5 BSC. BSC E H E H L TOP VIEW VARIATIONS: IM MIN.36 INCHES MAX.39 MILLIMETERS MIN MAX AA AB 9.. N MS 6 AC A C e B A FRONT VIEW L SIE VIEW - PACKAGE OUTLINE,.5" SOIC OCUMENT CONTROL NO. REV. - B

11 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 ÿ.5±. TOP VIEW E H X S BOTTOM VIEW IM A A MIN MAX BSC A.3 b c e E H L α S INCHES BSC MILLIMETERS MIN MAX BSC BSC LUMAX.EPS A A A e b c L α FRONT VIEW SIE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, L umax/usop APPROVAL OCUMENT CONTROL NO. REV. -36 J 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. Maxim Integrated Products, San Gabriel rive, Sunnyvale, CA 96 () Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.