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MAX1681ESA+T

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MAX1681ESA+T

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Part Number MAX1681ESA+T
Manufacturer Maxim Integrated
Description IC REG SWITCHD CAP INV 8SOIC
Datasheet MAX1681ESA+T Datasheet
Package 8-SOIC (0.154", 3.90mm Width)
In Stock 43,300 piece(s)
Unit Price $ 2.5459 *
Lead Time Can Ship Immediately
Estimated Delivery Time Sep 26 - Oct 1 (Choose Expedited Shipping)
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Part Number # MAX1681ESA+T (PMIC - Voltage Regulators - DC DC Switching Regulators) is manufactured by Maxim Integrated and distributed by Heisener. Being one of the leading electronics distributors, we carry many kinds of electronic components from some of the world’s top class manufacturers. Their quality is guaranteed by its stringent quality control to meet all required standards.

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MAX1681ESA+T Specifications

ManufacturerMaxim Integrated
CategoryIntegrated Circuits (ICs) - PMIC - Voltage Regulators - DC DC Switching Regulators
Datasheet MAX1681ESA+TDatasheet
Package8-SOIC (0.154", 3.90mm Width)
Series-
FunctionRatiometric
Output ConfigurationPositive or Negative
TopologyCharge Pump
Output TypeFixed
Number of Outputs1
Voltage - Input (Min)2V
Voltage - Input (Max)5.5V
Voltage - Output (Min/Fixed)-Vin, 2Vin
Voltage - Output (Max)-
Current - Output125mA
Frequency - Switching500kHz, 1MHz
Synchronous RectifierNo
Operating Temperature-40°C ~ 85°C (TA)
Mounting TypeSurface Mount
Package / Case8-SOIC (0.154", 3.90mm Width)
Supplier Device Package8-SOIC

MAX1681ESA+T Datasheet

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_______________General Description The MAX1680/MAX1681 inductorless switched-capaci- tor voltage converters either invert an input voltage of +2.0V to +5.5V or double it while supplying up to 125mA output current. They have a selectable-frequen- cy option that allows the use of small capacitors: 4.7µF (MAX1680), 1µF (MAX1681). With their high output cur- rent capability, these charge-pump devices are suit- able replacements for inductor-based regulators, which require more expensive external components and addi- tional board space. The devices’ equivalent output resistance (typically 3.5Ω ) allows them to deliver as much as 125mA with only a 440mV drop. A shutdown feature reduces quies- cent current to less than 1µA. The MAX1680/MAX1681 are available in 8-pin SO packages. For devices that deliver up to 50mA in smaller µMAX packages, refer to the MAX860/MAX861 data sheet. ________________________Applications Local Negative Supplies Interface Power Supplies Op-Amp Power Supplies MOSFET Bias ____________________________Features ♦ Selectable Switching Frequencies: 125kHz/250kHz (MAX1680) 500kHz/1MHz (MAX1681) ♦ Allow Use of Small Capacitors (1µF for the MAX1681) ♦ 125mA Output Current ♦ 3.5Ω Output Impedance ♦ 1µA Logic-Controlled Shutdown ♦ Configurable as Voltage Inverters or Doublers ♦ +2.0V to +5.5V Input Voltage Range ♦ Available in 8-Pin SO Packages ♦ 90% Efficiency M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters ________________________________________________________________ Maxim Integrated Products 1 MAX1681 FSEL IN CAP+ SHDN GND C1 1µF +VINPUT +3V TO +5.5V INVERTED OUTPUT VOLTAGEC2 1µF 1µF LV CAP- INVERTER CONFIGURATION OUT MAX1681 FSEL IN CAP+ SHDN GND C1 1µF C2 1µF DOUBLED OUTPUT VOLTAGE +VINPUT +4V TO +5.5V NOTE: USE 4.7µF CAPACITORS FOR MAX1680 INPUT VOLTAGE RANGE: +2.5V TO +5.5V. NOTE: USE 4.7µF CAPACITORS FOR MAX1680 INPUT VOLTAGE RANGE: +2.0V TO +5.5V. 1µF LV CAP- DOUBLER CONFIGURATION OUT __________________________________________________Typical Operating Circuits 19-1247; Rev 0; 7/97 PART MAX1680C/D MAX1680ESA MAX1681C/D 0°C to +70°C -40°C to +85°C 0°C to +70°C TEMP. RANGE PIN-PACKAGE Dice* 8 SO Dice* ______________Ordering Information *Contact factory for dice specifications. Pin Configuration appears at end of data sheet. MAX1681ESA -40°C to +85°C 8 SO For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.

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V M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters 2 _______________________________________________________________________________________ ABSOLUTE MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS (Typical Operating Circuits (inverter configuration), FSEL = LV = GND, VIN = 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°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. IN ..............................................................................-0.3V to +6V LV....................................................(VOUT - 0.3V) to (VIN + 0.3V) CAP+ ...........................................................-0.3V to (VIN + 0.3V) SHDN, FSEL ......................................(VLV - 0.3V) to (VIN + 0.3V) OUT, CAP- ..................................................................-6V to 0.3V Continuous Output Current ..............................................135mA Output Short-Circuit Duration to GND (Note 1) ...................1sec Continuous Power Dissipation (TA = +70°C) SO (derate 5.88mW/°C above +70°C)..........................471mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C ILOAD = 125mA Inverter configuration, RL = 1kΩ , LV = GND LV = GND (Note 3) FSEL = IN or LV SHDN = IN OUT = GND, SHDN = IN CONDITIONS 375 500 625 750 1000 1250 94 125 156 187 250 313 4VIH V-3.75 -4.56VLOAD Output Voltage Under Load (Note 2) V 3.0 5.5 2.0 5.5 V 1VIL Shutdown, FSEL Thresholds µA-1 1IFSELInput Bias Current (FSEL) Ω3.5 10ROUTOutput Resistance (Note 2) Ω1 5ROUT(SHUT) Output Resistance to Ground in Shutdown µA1I+SHDNShutdown Current µA-1 1ISHDNInput Bias Current (SHDN) UNITSMIN TYP MAXSYMBOLPARAMETER Doubler configuration, RL = 1kΩ , LV = OUT 4.0 5.5 VIN 2.5 5.5 Input Voltage Range MAX1680 5.4 mA 10.8 FSEL = IN (125kHz) FSEL = LV (250kHz) MAX1681 21.6 43.2 I+ FSEL = IN (500kHz) Supply Current FSEL = LV (1MHz) Note 1: Shorting OUT to IN may damage the device and should be avoided. TA = +25°C TA = +25°C TA = +25°C TA = +25°C MAX1681 MAX1680 MAX1681 MAX1680 TA = +25°C TA = +25°C TA = +25°C TA = +25°C 2.5 4.5 5 9 10 18 20 36 FSEL = LV 157 348 FSEL = IN MAX1680 79 174 FSEL = LV 570 1490 kHz FSEL = IN MAX1681 fOSCSwitching Frequency 285 745

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mA ELECTRICAL CHARACTERISTICS (Typical Operating Circuits (inverter configuration), FSEL = LV = GND, VIN = 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), TA = -40°C to +85°C, unless otherwise noted.) (Note 4) M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters _______________________________________________________________________________________ 3 FSEL = IN FSEL = LV MAX1681 ILOAD = 125mA 21.6 mA Inverter configuration, RL = 1kΩ , LV = GND 43.2 Doubler configuration, RL = 1kΩ , LV = OUT MAX1681 FSEL = LV FSEL = IN MAX1680 LV = GND (Note 3) FSEL = IN or LV SHDN = IN OUT = GND, SHDN = IN CONDITIONS I+ FSEL = IN (500kHz) Supply Current FSEL = LV (1MHz) kHz 285 745 fOSC 570 1490 79 174 157 348 Switching Frequency 4VIH V-3.75VLOAD Output Voltage Under Load (Note 2) 3.0 5.5 V 2.0 5.5 4.0 5.5 VIN V -1 1VIL Shutdown, FSEL Thresholds µA-1 1IFSELInput Bias Current (FSEL) Ω10ROUTOutput Resistance (Note 2) Ω5ROUT(SHUT) Output Resistance in Shutdown µA1I+SHDNShutdown Current µA1ISHDNInput Bias Current (SHDN) UNITSMIN TYP MAXSYMBOLPARAMETER MAX1681 MAX1680 2.5 5.5 Input Voltage Range MAX1681 MAX1680 MAX1680 5.4 10.8 FSEL = IN (125kHz) FSEL = LV (250kHz) ELECTRICAL CHARACTERISTICS (continued) (Typical Operating Circuits (inverter configuration), FSEL = LV = GND, VIN = 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) Note 2: C1 and C2 are low-ESR (<0.2Ω ) capacitors. Capacitor ESR adds to the circuit’s output resistance. Using capacitors with higher ESR reduces output voltage and efficiency. The specified output resistance includes the C1 and C2 0.2Ω ESR. Note 3: The typical threshold for VINPUT other than +5V is 0.35VINPUT (VIL = VIH). Note 4: Specifications to -40°C are guaranteed by design, not production tested. RL = 100Ω to GND, FSEL = IN MAX1680 MAX1681 % 80 90 Power Efficiency UNITSMIN TYP MAXSYMBOLPARAMETER CONDITIONS

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M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters 4 _______________________________________________________________________________________ __________________________________________Typical Operating Characteristics (All curves generated using the inverter configuration shown in the Typical Operating Circuits with LV = GND, FSEL = IN or LV, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), and TA = +25°C, unless otherwise noted. Test results are also valid for the doubler configuration with LV = OUT and TA = +25°C.) 2.5 3.5 5.5 4.5 7.5 6.5 8.5 2.52.0 3.0 3.5 4.0 4.5 5.0 5.5 OUTPUT SOURCE RESISTANCE vs. SUPPLY VOLTAGE M A X 1 6 8 0 /8 1 T O C 0 4 SUPPLY VOLTAGE (V) O U TP U T S O U R C E R ES IS TA N C E (Ω ) 0 1 3 2 5 4 6 -20-40 0 20 40 60 80 100 OUTPUT SOURCE RESISTANCE vs. TEMPERATURE M A X 1 6 8 0 /8 1 T O C 0 5 TEMPERATURE (°C) O U TP U T S O U R C E R ES IS TA N C E (Ω ) VINPUT = 3V VINPUT = 5V 100 0 1 100 1000 MAX1680 EFFICIENCY vs. LOAD CURRENT (INVERTER CONFIGURATION) 20 40 60 80 M A X 1 6 8 0 /8 1 T O C 0 6 LOAD CURRENT (mA) EF FI C IE N C Y ( % ) 10 VINPUT = 5.5V VINPUT = 4V VINPUT = 3V FSEL = IN 0 200 100 500 400 300 700 600 800 0 60 8020 40 100 120 140 OUTPUT VOLTAGE DROP vs. LOAD CURRENT M A X 1 6 8 0 /8 1 T O C 0 1 LOAD CURRENT (mA) O U TP U T V O LT A G E D R O P ( m V ) VINPUT = 3V VINPUT = 5V -14 -10 -12 -4 -6 -8 0 -2 2 2.0 3.5 4.02.5 3.0 4.5 5.0 5.5 OSCILLATOR FREQUENCY CHANGE vs. SUPPLY VOLTAGE M A X 1 6 8 0 /8 1 T O C 0 2 SUPPLY VOLTAGE (V) O S C IL LA TO R F R EQ U EN C Y C H A N G E (% ) MAX1680 MAX1681 -10 -6 -8 -2 -4 2 0 4 8 6 10 -40 0 20-20 40 60 80 100 OSCILLATOR FREQUENCY CHANGE vs. TEMPERATURE M A X 1 6 8 0 /8 1 T O C 0 3 TEMPERATURE (°C) O S C IL LA TO R F R EQ U EN C Y C H A N G E (% ) MAX1680 MAX1681

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M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters _______________________________________________________________________________________ 5 100 0 1 100 1000 MAX1681 EFFICIENCY vs. LOAD CURRENT (DOUBLER CONFIGURATION) 20 40 60 80 M A X 1 6 8 0 /8 1 T O C 0 7 LOAD CURRENT (mA) EF FI C IE N C Y ( % ) 10 VINPUT = 5.5V VINPUT = 4V VINPUT = 3V FSEL = IN 1 0 3 2 6 5 4 8 7 9 2.0 3.5 4.02.5 3.0 4.5 5.0 5.5 6.0 MAX1680 SUPPLY CURRENT vs. SUPPLY VOLTAGE M A X 1 6 8 0 /8 1 T O C 0 8 SUPPLY VOLTAGE (V) S U P P LY C U R R EN T (m A ) DOUBLER MODE FSEL = LV INVERTER MODE FSEL = IN INVERTER MODE FSEL = LV DOUBLER MODE FSEL = IN 0 5 15 10 25 20 30 3.02.5 3.5 4.0 4.5 5.0 5.5 6.0 MAX1681 SUPPLY CURRENT vs. SUPPLY VOLTAGE M A X 1 6 8 0 /8 1 T O C 0 9 SUPPLY VOLTAGE (V) S U P P LY C U R R EN T (m A ) DOUBLER MODE FSEL = LV INVERTER MODE FSEL = IN INVERTER MODE FSEL = LV DOUBLER MODE FSEL = IN 3 4 6 5 7 8 9 10 0 4 6 82 10 12 14 1816 20 MAX1680 OUTPUT SOURCE RESISTANCE vs. CAPACITANCE (INVERTER CONFIGURATION) M A X 1 6 8 0 /8 1 T O C 1 0 CAPACITANCE (µF) O U TP U T S O U R C E R ES IS TA N C E (Ω ) VINPUT = 3V, FSEL = LV VINPUT = 5V, FSEL = LV VINPUT = 3V, FSEL = IN VINPUT = 5V, FSEL = IN 3 4 6 5 7 8 9 10 0 4 6 82 10 12 14 1816 20 MAX1681 OUTPUT SOURCE RESISTANCE vs. CAPACITANCE (DOUBLER CONFIGURATION) M A X 1 6 8 0 /8 1 T O C 1 3 CAPACITANCE (µF) O U TP U T S O U R C E R ES IS TA N C E (Ω ) VINPUT = 3V, FSEL = LV VINPUT = 5V, FSEL = LV VINPUT = 5V, FSEL = IN VINPUT = 3V, FSEL = IN 3 4 6 5 7 8 9 10 0 4 6 82 10 12 14 1816 20 MAX1680 OUTPUT SOURCE RESISTANCE vs. CAPACITANCE (DOUBLER CONFIGURATION) M A X 1 6 8 0 /8 1 T O C 1 1 CAPACITANCE (µF) O U TP U T S O U R C E R ES IS TA N C E (Ω ) VINPUT = 3V, FSEL = LV VINPUT = 5V, FSEL = LV VINPUT = 5V, FSEL = IN VINPUT = 3V, FSEL = IN 3 4 6 5 7 8 9 10 0 4 6 82 10 12 14 1816 20 MAX1681 OUTPUT SOURCE RESISTANCE vs. CAPACITANCE (INVERTER CONFIGURATION) M A X 1 6 8 0 /8 1 T O C 1 2 CAPACITANCE (µF) O U TP U T S O U R C E R ES IS TA N C E (Ω ) VINPUT = 3V, FSEL = LV VINPUT = 5V, FSEL = LV VINPUT = 5V, FSEL = IN VINPUT = 3V, FSEL = IN ____________________________Typical Operating Characteristics (continued) (All curves generated using the inverter configuration shown in the Typical Operating Circuits with LV = GND, FSEL = IN or LV, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), and TA = +25°C, unless otherwise noted. Test results are also valid for the doubler configuration with LV = OUT and TA = +25°C.)

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_______________Detailed Description The MAX1680/MAX1681 switched-capacitor voltage converters either invert or double the input voltage. They have low output resistance (3.5Ω ) and can deliver up to 125mA output current. These devices operate at one of two selectable frequencies: 125kHz/250kHz (MAX1680) and 500kHz/1MHz (MAX1681). This pro- vides the flexibility to optimize capacitor size, operating supply current, and overall circuit efficiency. Frequency selection also allows for minimizing coupling into other sensitive circuits. These devices contain no internal divider; the oscillator frequency equals the switching frequency. The devices can easily be cascaded to pro- duce a higher output voltage, or paralleled to deliver more current. The MAX1680/MAX1681 feature a shutdown mode that reduces supply current to <1µA (SHDN = high). OUT, in the inverter configuration, pulls to ground in shut- down mode. Shutdown is not available in the doubler configuration; connect SHDN to OUT. __________Applications Information Voltage Inverter A simple voltage inverter is the most common MAX1680/MAX1681 application. It requires three exter- nal capacitors (including the input bypass capacitor) as shown in the Typical Operating Circuits (inverter configuration). Although the output is not regulated, low output resistance produces a typical drop of only 0.44V with a 125mA load. This low output resistance makes the devices fairly insensitive to changes in load (see the graphs for Output Source Resistance vs. Temperature and Supply Voltage in the Typical Operating Characteristics section). Voltage Doubler The MAX1680/MAX1681 can be configured as a volt- age doubler with two external capacitors as shown in the Typical Operating Circuits (doubler configuration). When loaded, the output voltage drop is similar to that of the voltage inverter. The minimum input supply range is slightly higher than in the inverter configuration. Calculate ripple voltage using the equation in the Capacitor Selection section. Frequency Control A frequency-control pin, FSEL, provides design flexibili- ty. Each device has two selectable frequencies: 125kHz/250kHz (MAX1680) and 500kHz/1MHz (MAX1681). This allows optimization of capacitor size and supply current for a given output load. Table 1 summarizes the frequency options . Table 1. Nominal Switching Frequencies M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters 6 _______________________________________________________________________________________ ______________________________________________________________Pin Description Selects operating frequency. MAX1680: 250kHz when FSEL is low, 125kHz when FSEL is high. MAX1681: 1MHz when FSEL is low, 500kHz when FSEL is high. FSEL1 Positive Charge-Pump Capacitor ConnectionCAP+2 Negative Charge-Pump Capacitor ConnectionCAP-4 Power-Supply Ground InputGND3 Logic Voltage Input. Connect LV to GND.LV6 Power-Supply Positive Voltage InputIN8 SHDN7 Negative Voltage OutputOUT5 Power-Supply Positive Voltage Input Power-Supply Ground Connection Connect LV to OUT. Not available; connect to OUT. Shutdown Input. Driving SHDN high disables the charge pump, and the output goes to 0V. SHDN is a CMOS input. Positive Voltage Output MAX1680 250FSEL = LV 125FSEL = IN FSEL CONNECTION MAX1681 1000 500 FREQUENCY (kHz) INVERTER DOUBLER PIN FUNCTION NAME

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Operating Frequency Trade-Offs It is important to recognize the trade-offs between switching frequency, power consumption, noise, cost, and performance. Higher frequency switching reduces capacitor size while maintaining the same output impedance, thus saving capacitor cost and board space. Lower frequency designs use less supply cur- rent. Table 2 summarizes the relative trade-offs. Table 2. Switching-Frequency Trade-Offs Capacitor Selection The MAX1680/MAX1681 are tested with capacitor val- ues of 10µF and 2.2µF, respectively. Capacitor size and switching speed determine output resistance. Larger C1 values decrease the output resistance until the internal switch resistance (3.5Ω typ) becomes the dominant term. Low-ESR capacitors minimize output resistance and ripple voltage. The entire circuit’s output resistance can be approximated by the following equa- tion: ROUT ≅ RO + 4 x ESRC1 + ESRC2 + [1 / (fOSC x C1)] + [1 / (fOSC x C2)] where RO is the device’s internal effective switch resis- tance and fOSC is the switching frequency. Output resistance is a critical circuit component, as it deter- mines the voltage drop that will occur at the output from the ideal value of -VINPUT (or 2VINPUT when doubling). To optimize performance, minimize overall resistance in the system. In particular, equivalent series resistance (ESR) in the capacitors produces significant losses as large currents flow through them. Therefore, choose a low-ESR capacitor for highest efficiency. Table 3 lists recommended capacitors and their suppliers. Calculate the output ripple voltage as follows: VRIPPLE = [(IOUT) / (2 x fOSC x C2)] + 2 x (IOUT x ESRC2) where IOUT is the load current, fS is the charge pump’s operating frequency, C2 is the output capacitor, and ESRC2 is the output capacitor’s ESR. Table 4 lists the minimum recommended capacitances that allow for the maximum output current. The output capacitor, C2, is normally equal to or greater than the charge-pump capacitor, C1. Capacitor values can be scaled directly proportional to the input voltage, fre- quency, and load current. For example, for VINPUT = 5V, ILOAD = 125mA at fOSC = 125kHz, a 6.4µF mini- mum capacitor is recommended. For an output of only 62.5mA, a 3.2µF capacitor is recommended. C1’s value can be estimated as follows: C1 = 6.4µF x (VINPUT / 5.0V) x (125kHz / fOSC) x (ILOAD / 125mA) where fOSC is the switching frequency (kHz) and ILOAD is the output current (mA) required. M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters _______________________________________________________________________________________ 7 ATTRIBUTE C1, C2 Values Larger LOWER FREQUENCY Output Ripple Larger Smaller Smaller SUPPLIER Marcon/United Chemi-Con (847) 696-2000 PHONE AVX (803) 946-0690 (800) 282-4975 (847) 696-9278 (803) 626-3123 HIGHER FREQUENCY Supply Current Smaller Larger FAX DEVICE TYPE Ceramic capacitors Surface mount, TPS series Matsuo (714) 969-2491 (714) 960-6492 Surface mount, 267 series Nichicon USA: (847) 843-7500 Japan: 81-7-5231-8461 USA: (847) 843-2798 Japan: 81-7-5256-4158 Sanyo USA: (619) 661-6835 Japan: 81-7-2070-6306 USA: (619) 661-1055 Japan: 81-7-2070-1174 Through-hole, OS-CON series Through-hole, PL series Sprague (603) 224-1961 (603) 224-1430 TDK (847) 390-4373 (847) 390-4428 Ceramic capacitors Surface mount, 595D series United Chemi-Con (714) 255-9500 (714) 255-9400 Vishay/Vitramon (203) 268-6261 (203) 452-5670 SMT ceramic chip capacitors Through-hole, LXF series Table 3. Low-ESR Capacitor Suppliers

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M A X 1 6 8 0 /M A X 1 6 8 1 Bypass Capacitor Bypass the input voltage to reduce AC impedance and to prevent internal switching noise. Bypassing depends on the source impedance location. The AC ripple cur- rent is 2 x IOUT for the doubler and the inverter. Use a large bypass capacitor (equal to C1) if the supply has high AC impedance. Cascading Devices To produce larger negative voltages, cascade two devices (Figure 1). For two devices, the unloaded out- put voltage is approximately -2 x VINPUT, but this value is reduced slightly by the first device’s output resis- tance multiplied by the second device’s quiescent cur- rent. The effective output resistance for a cascaded device is larger than that for an individual device (20Ω for two devices). Cascading several devices increases output resistance and reduces efficiency. If a large negative voltage is required for several stages, an inductive inverting switching regulator such as the MAX629 or MAX774 may offer more advantages. Paralleling Devices Parallel two or more MAX1680/MAX1681s to reduce output resistance voltage drop under a given load. With reduced output resistance, paralleled devices deliver higher load currents. Figure 2 shows two MAX1680/MAX1681s connected in parallel. Output resistance is inversely proportional to the number of devices. 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters 8 _______________________________________________________________________________________ 250 1.2 125 2.5 1.9 3.8 500 0.6 0.9 Table 4. Minimum Recommended Capacitances for Maximum Output Current CAPACITANCE (µF) (C1 = C2) 2.5 5.1 3.2 6.4 1.2 1.6 1000 0.3 0.4 0.6 0.8 VIN = 3V fOSC (kHz) VIN = 2V VIN = 5VVIN = 4V MAX1681 FSEL IN CAP+ SHDN GND1µF 1µF 1µF LV CAP- OUT MAX1681 FSEL IN CAP+ SHDN GND +VINPUT VOUT = -VINPUT 1µF NOTE: USE 4.7µF CAPACITORS FOR MAX1680. 1µF LV CAP- OUT VOUT = -2VINPUT Figure 1. Cascading MAX1680/MAX1681s to Increase Output Voltage

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Combined Doubler and Inverter Figure 3 shows a single MAX1680/MAX1681 as an inverter and a doubler. The maximum output current is the sum of the loads on the two outputs and is still limit- ed to 125mA. As the device is loaded, the output volt- ages move toward ground. In this particular configuration, connect LV to GND (inverter). The diodes used in the circuit cause a drop of approximately 0.7V in the doubler’s output voltage, impacting efficiency. Compatibility with the MAX660 and MAX860/MAX861 The MAX1680/MAX1681 can be used in place of the MAX860/MAX861, except for the SHDN and FSEL pins. The MAX1680/MAX1681 shut down with a high input voltage, compared with the MAX860/MAX861. The MAX1680/MAX1681 have only two frequency choices. Replacing the MAX660 with the MAX1680/MAX1681 involves a wiring change, as the external oscillator pin is replaced by the shutdown feature. Table 5 compares the devices. M A X 1 6 8 0 /M A X 1 6 8 1 125mA, Frequency-Selectable, Switched-Capacitor Voltage Converters _______________________________________________________________________________________ 9 MAX1681 FSEL IN +VINPUT CAP+ SHDN GND1µF 1µF LV CAP- OUT GND MAX1681 "n" FSEL IN CAP+ SHDN 1µF 1µF 1µF VOUT NOTE: USE 4.7µF CAPACITORS FOR MAX1680. VOUT = -VINPUT LV CAP- OUT ROUT = ROUT OF SINGLE DEVICE NUMBER OF DEVICES (n) Figure 2. Paralleling MAX1680/MAX1681s to Increase Output Current MAX1681 FSEL IN +VINPUT CAP+ SHDN GND1µF 1µF 1µF 1µF 1µF LV CAP- OUT VOUT = -VINPUT D1 IN4148 D2 IN4148 VOUT = 2VINPUT -VFD1 -VFD2 NOTE: USE 4.7µF CAPACITORS FOR MAX1680. Figure 3. Combined Doubler and Inverter

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hotMCP73855T-I/MF MCP73855T-I/MF Microchip Technology, IC CONTROLLER LI-ION 4.1V 10DFN, 10-VFDFN Exposed Pad, - View
CP12637_LAURA-WW-PG CP12637_LAURA-WW-PG Ledil, ASSEMBLY SQUARE 1 POS 21.6MM D 1, -, - View
OP269A OP269A TT Electronics/Optek Technology, EMITTER IR 890NM 50MA RADIAL, Radial, - View
P0250.332NL P0250.332NL Pulse Electronics Power, FIXED IND 3.3UH 6.2A 15 MOHM SMD, Nonstandard, - View
ESQT-114-02-L-Q-530 ESQT-114-02-L-Q-530 Samtec Inc., ELEVATED 2MM SOCKETS, -, - View
ESQT-113-03-G-D-375 ESQT-113-03-G-D-375 Samtec Inc., ELEVATED 2MM SOCKETS, -, - View
MS27468T25Z29A MS27468T25Z29A Souriau, 8LT 29C 29#16 PIN J/N, -, - View
GBM10DTKI-S288 GBM10DTKI-S288 Sullins Connector Solutions, CONN EDGE DUAL FMALE 20POS 0.156, -, - View
VI-B6M-CW-S VI-B6M-CW-S Vicor Corporation, CONVERTER MOD DC/DC 10V 100W, Full Brick, - View
ISL6369CRZ ISL6369CRZ Renesas Electronics America, IC REG 1-6 PHASE CTRLT VR 60QFN, 60-VFQFN Exposed Pad, - View
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MAX1681ESA+T

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Heisener's commitment to quality has shaped our processes for sourcing, testing, shipping, and every step in between. This foundation underlies each component we sell.

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