Rainbow-electronics MAX773 User Manual

_______________General DescriptionThe MAX770–MAX773 step-up switching controllers pro-vide 90% efficiency over a 10mA to 1A load. A unique current-lim

MAX770–MAX773frequencies (up to 300kHz), allowing the use of tinyexternal components.As with traditional PFM converters, the power transistoris not tu

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers_____________________________________________________________

MAX770–MAX773turned on, it stays on until either 1) the maximum on-time one-shot turns it off (typically 16µs later), or 2) theswitch current reaches

drive outputs (EXTH and EXTL) that operate 180° out ofphase (Figures 3a and 3b). In Figure 3b, the resistor inseries with EXTH limits the base current

MAX770–MAX773Use an N-channel FET as the power switch when usingthe shunt regulator (see MAX773 Shunt-RegulatorOperationin the Detailed Description).

Determining RSENSE The Typical Operating Characteristicsgraphs show theoutput current capability for various modes, senseresistors, and input/output v

MAX770–MAX773The standard operating circuits use a 22µH inductor. If a different inductance value is desired, select Lsuch that:VIN(max) x tON(min)L ≥

The two most significant losses contributing to the N-FET’s power dissipation are I2R losses and switchinglosses. Select a transistor with low rDS(ON)

MAX770–MAX773Smaller capacitors are acceptable for light loads or inapplications that can tolerate higher output ripple. Since the output filter capac

Starting Up under LoadThe Typical Operating Characteristicsshow the Start-Up Voltage vs. Load Current graph for bootstrapped-mode operation. This grap

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers2____________________________________________________________

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers20___________________________________________________________

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers_____________________________________________________________

01234-75-50 -25 025 50 75 100 125SUPPLY CURRENT vs. TEMPERATURETEMPERATURE (°C)SUPPLY CURRENT (mA)VOUT = 12V, VIN = 5VCIRCUIT OF FIGURE 2bBOOTSTRAPPED

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers_____________________________________________________________

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers6____________________________________________________________

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers_____________________________________________________________

MAX770–MAX7735V/12V/15V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controllers8____________________________________________________________

Floating the shunt-regulator ground (SGND) disablesthe shunt regulator. To enable it, connect SGND toGND. The shunt regulator requires 1mA minimum cur