Features: ` Up to 96% Efficiency
` 1A Guaranteed Output Current
` 100% Duty Cycle in Dropout
` 2.7V to 14V Input Range (15V absolute max)
` ±1% Accurate Reference Output
` 0.24 P-Channel On-Resistance
` Synchronizable Switching Frequency
` Fixed-Frequency PWM Operation
300kHz (MAX1684)
600kHz (MAX1685)
` 150A Normal Mode Quiescent Current
` 25A Low-Power Mode Quiescent Current
` 2A Shutdown Current
` Dual Mode™ Fixed 3.3V (±1%) Output or Adjustable Output (1.25V to VIN)
` Small 16-QSOP Package
` Auxiliary Output (CVL): 3V/5mAApplicationCellular Phones
2-Way Radios and Walkie-Talkies
Computer Peripherals
Personal Communicators
PDAs and Handy-TerminalsPinout
SpecificationsAIN to AGND ......................................................-0.3 to +15V
IN to PGND ..........................................-0.3V to (VAIN + 0.3V)
LX to PGND ............................................-0.5V to (VIN + 0.3V)
PGND to AGND ............................................................±0.3V
SHDN to AGND ....................................-0.3V to (VAIN + 0.3V)
ILIM/SS, FB, CC, BOOT, REF to AGND ...-0.3V to (VCVL+ 0.3V)
CVH to IN..........................................................-6V to +0.3V
CVL, STBY, SYNC/PWM to AGND........................-0.3V to +6V
Reference Current .....................................................±1mA
CVL Current ...................................................10mA to -1mA
LX Peak Current (Internally Limited) .............................2.3A
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)......667mW
Operating Temperature Range ..................-40°C to +85°C
Junction Temperature...............................................+150°C
Storage Temperature Range ...................-65°C to +150°C
Lead Temperature (soldering, 10sec ) .....................+300°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.
DescriptionThe MAX1684/MAX1685 are high-efficiency, internalswitch,PWM step-down switching regulators intended to power cellular phones, communicating PDAs, and handy-terminals. These devices deliver a guaranteed 1A output current from two Li-Ion batteries. Their wide input voltage range of 2.7V to 14V gives design flexibility and allows batteries to charge from a wall cube, since the ICs operate at the higher voltages that occur when the battery is removed. The output voltage is preset to 3.3V or can be externally adjusted from 1.25V to VIN.
The low-on-resistance power switch and built-in synchronous rectifier provide high efficiencies of up to 96%.There are four modes of operation: fixed-frequency mode, normal mode, low-power mode, and shutdown mode. The fixed-frequency PWM mode of operation offers excellent noise characteristics. The normal mode maintains high efficiency at all loads. The low-power mode is used to conserve power in standby or when full load is not required. The shutdown mode is used to power down the device for minimal current draw.
The MAX1684 runs at 300kHz for applications that require highest efficiency. The MAX1685 runs at 600kHz to allow use of smaller external components. These devices can also be synchronized to an external clock. Other features include a 100% duty cycle for low-dropout applications, an auxiliary 3V/5mA output,and a 1% accurate reference.
Both devices are available in a space-saving 16-QSOP package. An evaluation kit is also available to help speed designs. For a similar device in a 10-pin MAX package with lower input voltage requirements (5.5V max), see the MAX1692 data sheet.
MAX1684 Data Sheet
