MAX770 Maxim Integrated Products, MAX770 Datasheet
MAX770
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MAX770 Summary of contents
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... The MAX770/MAX771/MAX772 accept input voltages from 2V to 16.5V. Output voltages are preset at 5V, (MAX770), 12V (MAX771), and 15V (MAX772); they can also be adjusted using two resistors. The MAX773 accepts inputs from 3V to 16.5V. For a wider input range, it features an internal shunt regulator that allows unlimited higher input voltages. The MAX773’ ...
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... MAX77_C_ _/E_ _ ..........................................................+150°C MAX77_MJ_..................................................................+175°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C , unless otherwise noted. Typical values are at T CONDITIONS MAX770–772 (internal feedback resistors) MAX770–772C/E (external resistors) MAX770–772MJA (external resistors) MAX773C/E MAX773MJD MAX770/MAX771/MAX772 V+ = 16.5V, SHDN = 0V (normal operation 10.0V, SHDN ≥ ...
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Adjustable, High-Efficiency, ELECTRICAL CHARACTERISTICS (continued) ( 0mA LOAD A MIN PARAMETERS SYMBOL REF Load Regulation REF Line Regulation FB Trip-Point Voltage V FB Input Current I SHDN Input High ...
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... 12V 60 OUT CIRCUIT OF FIGURE 2b 50 0.001 0.01 0.1 1 OUTPUT CURRENT (A) MAX770 LOAD CURRENT vs. MINIMUM START-UP INPUT VOLTAGE 700 OUT 600 CIRCUIT OF FIGURE 2a 500 400 300 ABOVE 3.4V, THE CIRCUIT 200 STARTS UP UNDER MAXIMUM 100 LOAD CONDITIONS 0 1.0 1.5 2.0 2.5 3.0 3 ...
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Adjustable, High-Efficiency, ____________________________Typical Operating Characteristics (continued +25°C, unless otherwise noted.) A REFERENCE OUTPUT RESISTANCE vs. TEMPERATURE 250 200 150 100 50 0 -60 -40 - TEMPERATURE ( C) MAXIMUM SWITCH ON-TIME vs. TEMPERATURE 16.5 ...
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... TO 4.5V, 2V/div RIPPLE, 100mV/div, AC-COUPLED OUT _______________________________________________________________________________________ 6 LIGHT-LOAD SWITCHING WAVEFORMS A I LIM 3V 165mA OUT A: EXT VOLTAGE, 5V/div B: INDUCTOR CURRENT, 1A/div C: V RIPPLE 100mV/div, AC-COUPLED OUT LOAD-TRANSIENT RESPONSE LOAD CURRENT 0.5A/div ( RIPPLE, 100mV/div, AC-COUPLED OUT MAX770 s/div MAX770 A B 2ms/div ...
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... EXT Gate drive for external N-channel power transistor Power-supply input. Also acts as a voltage-sense point when in bootstrapped mode for the MAX770/MAX771/MAX772 shunt regulator when SGND is connected to ground for the MAX773. Bypass to SGND with 0.1 F when using the shunt regulator. Feedback input for adjustable-output operation. Connect to ground for fixed-output operation. Use ...
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... MOSFET’s gate capacitance. The minimum input voltage for the MAX770–MAX773 is 3V when using external feedback resistors. With supply voltages below 5V, bootstrapped mode is recommended. Note: When using the MAX770/MAX771/MAX772 in ...
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... LOW-VOLTAGE OSCILLATOR CURRENT-SENSE AMPLIFIER 0.2V The MAX770–MAX773 use a proprietary current-limited PFM control scheme to provide high efficiency over a wide range of load currents. This control scheme com- bines the ultra-low supply current of PFM converters (or pulse skippers) with the high full-load efficiency of PWM converters. ...
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... As with traditional PFM converters, the power transistor is not turned on until the voltage comparator senses that the output is out of regulation. However, unlike tra- ditional PFM converters, the MAX770–MAX773 switch using the combination of a peak current limit and a pair of one-shots that set the maximum on-time (16µs) and ...
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Adjustable, High-Efficiency V12 14 V15 SGND R4 8 63.4k REF MAX773 (1 LBO 0 LBI 13 EXTH EXTL SHDN 10k ...
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... V = 1.5V REF Figure 4. MAX773 Shunt Regulator The MAX770/MAX771/MAX772 feature a low input volt- age start-up oscillator that guarantees start-up with no load down to 2V when operating in bootstrapped mode and using internal feedback resistors. At these low volt- ages, the supply voltage is not large enough for proper error-comparator operation and internal biasing ...
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... In Figure 3b, the resistor in series with EXTH limits the base current, and EXTL (which is connected directly to the base) turns the transistor off. When SHDN is high, the MAX770–MAX773 enter shut- down mode. In this mode, the internal biasing circuit turned off (including the reference) and V ...
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... This provides adequate biasing SHUNT current for this circuit, although higher shunt currents can be used. ______________________________________________________________________________________ 14 BOOTSTRAPPED* GND to V OUT Lower Higher Higher 2V to 16.5V (MAX770/MAX771/MAX772), (internal feedback resistors 16.5V (MAX770/MAX771/MAX772), (external feedback resistors 16.5V (MAX773 (MAX770/MAX771/MAX772 (MAX773) MAX770–MAX773(N) MAX770–MAX773( SHUNT V+ ...
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Adjustable, High-Efficiency, 3 OUT 3 40m SENSE 2 50m SENSE 2.0 R SENSE 1.5 1.0 R SENSE 0.5 R SENSE INPUT VOLTAGE (V) Figure ...
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... L Table 2 lists inductor suppliers and specific recom- mended inductors. N Use an N-channel MOSFET power transistor with the MAX770/MAX771/MAX772 (Figure 8a). Use an N-FET whenever possible with the MAX773. An NPN transistor can be used, but be extremely careful R SENSE when determining the base current (see NPN Transistors section) ...
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... T voltage and a high current gain. A good transistor to use is the Zetex ZTX694B. The MAX770–MAX773’s high switching frequency of TH demands a high-speed rectifier. Schottky diodes such as the 1N5817–1N5822 are recommended. Make sure NPN Transistors that the Schottky diode’ ...
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... The input bypass capacitor (C1) reduces peak currents drawn from the voltage source and also reduces noise at the voltage source caused by the switching action of the MAX770–MAX773. The input voltage source imped- ance determines the size of the capacitor required at the V+ input. As with the output filter capacitor, a low- ESR capacitor is recommended. For output currents up to 1A, 150µ ...
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... The Typical Operating Characteristics show the Start- Up Voltage vs. Load Current graph for bootstrapped- mode operation. This graph depends on the type of power switch used. The MAX770–MAX773 are not designed to start up under full load in boot- strapped mode with low input voltages. Layout Considerations ...
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... Plastic DIP 14 Narrow SO 14 CERDIP TRANSISTOR COUNT: 501; SUBSTRATE CONNECTED TO V+. V+ LBO V15 EXTH EXTL LBI CS SGND GND FB REF TRANSISTOR COUNT: 501; SUBSTRATE CONNECTED TO V+. MAX770/MAX771/MAX772 EXT CS 0.126" (3.200mm) GND AGND SHDN REF 0.080" (2.032mm) MAX773 V5 V12 V15 EXTH EXTL CS SGND 0.126" ...