Datasheet MAX1771 (Maxim) - 7
| Manufacturer | Maxim |
| Description | 12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller |
| Pages / Page | 16 / 7 — 12V or Adjustable, High-Efficiency,. Low IQ, Step-Up DC-DC Controller. … |
| File Format / Size | PDF / 782 Kb |
| Document Language | English |
12V or Adjustable, High-Efficiency,. Low IQ, Step-Up DC-DC Controller. Detailed Description
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MAX1771
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Detailed Description
range of load currents; and 3) the maximum supply current is only 110µA. The MAX1771 is a BiCMOS, step-up, switch-mode power-supply controller that provides a preset 12V out- The device has a shutdown mode that reduces the put, in addition to adjustable-output operation. Its supply current to 5µA max. unique control scheme combines the advantages of
Bootstrapped/Non-Bootstrapped Modes
pulse-frequency modulation (low supply current) and Figure 2 shows the standard application circuits for pulse-width modulation (high efficiency with heavy bootstrapped and non-bootstrapped modes. In boot- loads), providing high efficiency over a wide output strapped mode, the IC is powered from the output current range, as well as increased output current (VOUT, which is connected to V+) and the input voltage capability over previous PFM devices. In addition, the range is 2V to VOUT. The voltage applied to the gate of external sense resistor and power transistor allow the the external power transistor is switched from VOUT to user to tailor the output current capability for each appli- ground, providing more switch gate drive and thus cation. Figure 1 shows the MAX1771 functional diagram. reducing the transistor’s on-resistance. The MAX1771 offers three main improvements over In non-bootstrapped mode, the IC is powered from the prior pulse-skipping control solutions: 1) the converter input voltage (V+) and operates with minimum supply operates with miniature (5mm height and less than current. In this mode, FB is the output voltage sense 9mm diameter) surface-mount inductors due to its point. Since the voltage swing applied to the gate of the 300kHz switching frequency; 2) the current-limited PFM external power transistor is reduced (the gate swings control scheme allows 90% efficiencies over a wide from V+ to ground), the power transistor’s on-resistance REF FB DUAL-MODE COMPARATOR SHDN MAX1771 50mV BIAS 1.5V CIRCUITRY REFERENCE ERROR COMPARATOR MIN OFF-TIME ONE-SHOT Q TRIG V+ N 2.3µs F/F S Q R LOW-VOLTAGE 2.5V MAX ON-TIME OSCILLATOR ONE-SHOT TRIG Q 16µs EXT CURRENT-SENSE 0.1V AMPLIFIER CS Figure 1. Functional Diagram Maxim Integrated 7
12V or Adjustable, High-Efficiency, Low IQ, Step-Up DC-DC Controller Detailed Description
range of load currents; and 3) the maximum supply current is only 110µA. The MAX1771 is a BiCMOS, step-up, switch-mode power-supply controller that provides a preset 12V out- The device has a shutdown mode that reduces the put, in addition to adjustable-output operation. Its supply current to 5µA max. unique control scheme combines the advantages of
Bootstrapped/Non-Bootstrapped Modes
pulse-frequency modulation (low supply current) and Figure 2 shows the standard application circuits for pulse-width modulation (high efficiency with heavy bootstrapped and non-bootstrapped modes. In boot- loads), providing high efficiency over a wide output strapped mode, the IC is powered from the output current range, as well as increased output current (VOUT, which is connected to V+) and the input voltage capability over previous PFM devices. In addition, the range is 2V to VOUT. The voltage applied to the gate of external sense resistor and power transistor allow the the external power transistor is switched from VOUT to user to tailor the output current capability for each appli- ground, providing more switch gate drive and thus cation. Figure 1 shows the MAX1771 functional diagram. reducing the transistor’s on-resistance. The MAX1771 offers three main improvements over In non-bootstrapped mode, the IC is powered from the prior pulse-skipping control solutions: 1) the converter input voltage (V+) and operates with minimum supply operates with miniature (5mm height and less than current. In this mode, FB is the output voltage sense 9mm diameter) surface-mount inductors due to its point. Since the voltage swing applied to the gate of the 300kHz switching frequency; 2) the current-limited PFM external power transistor is reduced (the gate swings control scheme allows 90% efficiencies over a wide from V+ to ground), the power transistor’s on-resistance REF FB DUAL-MODE COMPARATOR SHDN MAX1771 50mV BIAS 1.5V CIRCUITRY REFERENCE ERROR COMPARATOR MIN OFF-TIME ONE-SHOT Q TRIG V+ N 2.3µs F/F S Q R LOW-VOLTAGE 2.5V MAX ON-TIME OSCILLATOR ONE-SHOT TRIG Q 16µs EXT CURRENT-SENSE 0.1V AMPLIFIER CS Figure 1. Functional Diagram Maxim Integrated 7
