MAXIM Electronic Components

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The MAX1649/MAX1651 BiCMOS, step-down, DC-DC switching controllers provide high efficiency over loads ranging from 1mA to more than 2.5A. A unique, currentlimited pulse-frequency-modulated (PFM) control scheme gives these devices the benefits of pulse-width-modulation (PWM) converters (high efficiency at heavy loads), while using only 100µA of supply current (vs. 2mA to 10mA for PWM converters). Dropout performance down to 300mV is provided by a high switch duty cycle (96.5%) and a low current-sense threshold (110mV). A high switching frequency (up to 300kHz) allows these devices to use miniature external components. The MAX1649/MAX1651 have dropout voltages less than 0.3V at 500mA and accept input voltages up to 16V. Output voltages are preset at 5V (MAX1649), or 3.3V (MAX1651). They can also be adjusted to any voltage from 1.5V to the input voltage by using two resistors.

These step-down controllers drive external P-channel MOSFETs at loads greater than 12.5W. If less power is required, use the MAX639/MAX640/MAX653 step-down converters with on-chip FETs, which allow up to a 225mA load current.

Applications

• PDAs
• High-Efficiency Step-Down Regulation
• 5V-to-3.3V Green PC Applications
• Battery-Powered Applications

Features

• More than 90% Efficiency (10mA to 1.5A Loads)
• More than 12.5W Output Power
• Less than 0.3V Dropout Voltage at 500mA
• 100µA Max Quiescent Supply Current
• 5µA Max Shutdown Supply Current
• 16V Max Input Voltage
• 5V (MAX1649), 3.3V (MAX1651), or Adjustable

Output Voltage

• Current-Limited Control Scheme
• Up to 300kHz Switching Frequency
• Up to 96.5% Duty Cycle

Ordering Information

• Dice are tested at TA = +25°C.

Typical Operating Circuit

• PART TEMP. RANGE PIN-PACKAGE
• MAX1651ESA -40°C to +85°C 8 SO

http://datasheets.maxim-ic.com/en/ds/MAX1649-MAX1651.pdf

The MAX706P/R/S/T, MAX706AP/AR/AS/AT, and MAX708R/S/T microprocessor (µP) supervisory circuits reduce the complexity and number of components required to monitor +3V power-supply levels in +3V to +5V µP systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components.

The MAX706P/R/S/T and MAX706AP/AR/AS/AT supervisory circuits provide the following four functions:

1) A reset output during power-up, power-down, and brownout conditions. 2) An independent watchdog output that goes low if thewatchdog input has not been toggled within 1.6s. 3) A 1.25V threshold detector for power-fail warning, low-battery detection, or for monitoring a power supply other than the main supply. 4) An active-low, manual-reset input.

The only difference between the MAX706R/AR, MAX706S/AS, and MAX706T/AT is the reset-threshold voltage levels, which are 2.63V, 2.93V, and 3.08V, respectively. All have active-low reset output signals. The MAX706P/AP are identical to the MAX706R/AR, except the reset output signal is active-high. The watchdog timer function for the MAX706AP/AR/AS/AT disables when the WDI input is left open or connected to a high-impedance state of a low-leakage tri-state output. The MAX708R/S/T provide the same functions as the MAX706R/S/T and MAX706AR/AS/AT except they do not have a watchdog timer. Instead, they provide both RESET and RESET outputs. As with the MAX706, devices with R, S, and T suffixes have reset thresholds of 2.63V, 2.93V, and 3.08V, respectively.

These devices are available in 8-pin SO, DIP, and µMAX® packages and are fully specified over the operating temperature range.

• µMAX Package, Small 8-Pin SO
• Precision Supply-Voltage Monitors
• 2.63V (MAX706P/R, MAX706AP/AR, and MAX708R)
• 2.93V (MAX706S, MAX706AS, and MAX708S)
• 3.08V (MAX706T, MAX706AT, and MAX708T)
• 200ms Reset Time Delay
• Debounced TTL/CMOS-Compatible Manual Reset
• Input
• 100µA Quiescent Current
• WDI Disable Feature (MAX706AP/AR/AS/AT)
• Watchdog Timer: 1.6s Timeout
• Reset Output Signal:
• Active-High Only (MAX706P, MAX706AP)
• Active-Low Only (MAX706R/S/T, MAX706AR/AS/AT)
• Active-High and Active-Low (MAX708R/S/T)
• Voltage Monitor for Power-Fail or Low-Battery
• Warning
• 8-Pin Surface-Mount Package
• Guaranteed RESET Assertion to VCC = 1V

• PART†TEMP
• RANGE
• PINPACKAGE
• PKG
• CODE
• MAX706PCPA 0°C to +70°C 8 PDIP P8-1
• MAX706PCSA 0°C to +70°C 8 SO S8-2
• MAX706PCUA 0°C to +70°C 8 µMAX U8-1
• MAX706PEPA -40°C to +85°C 8 PDIP P8-1
• †SO, µMAX, and PDIP packages are available in lead-free.

http://datasheets.maxim-ic.com/en/ds/MAX706AP-MAX708T.pdf

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