MAX1856EUB+TG05

19-1898; Rev 0; 2/01 Wide Input Range, Synchronizable, PWM SLIC Power Supply The MAX1856 offers a low-cost solution for generating a SLIC (ringer and off-hook) power supply. Using standard off-the-shelf transformers from multiple vendors, the MAX1856 generates various output voltages: -24V and -72V (dual output) for both ringer and off-hook supplies for voice-enabled broadband consumer premises equipment (CPE), -48V for IP phones and routers, -5V and -15V (single or dual output) for DSL CO line drivers, or negative voltages as high as -185V for MEMS bias supplies. The output voltages are adjusted with an external voltage divider. Due to its wide operating voltage range, the MAX1856 operates from a low-cost, unregulated DC power supply for cost-sensitive applications like xDSL, cable modems, set-top boxes, LMDS, MMDS, WLL, and FTTH CPE. The MAX1856 provides low audio-band noise for talk battery and a sturdy output capable of handling the ring trip conditions for ring battery. The operating frequency can be set between 100kHz and 500kHz with an external resistor in free-running mode. For noise-sensitive applications, the MAX1856’s operating frequency can be synchronized to an external clock over its operating frequency range. The flyback topology allows operation close to 50% duty cycle, offering high transformer utilization, low ripple current, and less stress on input and output capacitors. Internal soft-start minimizes startup stress on the input capacitor, without any external components. The MAX1856’s current-mode control scheme does not require external loop compensation. The low-side currentsense resistor provides accurate current-mode control and overcurrent protection. Applications VoIP Ringer and Off-Hook Voltage Generators Cable and DSL Modems Set-Top Boxes Wireless Local Loop FTTH LMDS/MMDS Routers Industrial Power Supplies CO DSL Line Driver Supplies MEMS Bias Supplies Features ♦ Low-Cost, Off-the-Shelf Transformer ♦ 3V to 28V Input Range ♦ Low Audio-Band Noise on Talk Battery ♦ Effectively Handles Ring Trip Transients ♦ Powers 2-, 4-, or 12-Line Equipment ♦ High Efficiency Extends Battery Life During Life-Line Support Conditions ♦ Adjustable 100kHz to 500kHz Switching Frequency ♦ Clock Synchronization ♦ Internal Soft-Start ♦ Current-Mode PWM and Idle Mode™ Control Scheme ♦ Logic-Level Shutdown ♦ 10-Pin µMAX Package Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX1856EUB -40°C to +85°C 10 µMAX Typical Operating Circuit INPUT 3V TO 28V OUT2 -72V 1 VCC 2 SYNC/SHDN LDO EXT 2 OUT1 -24V CS FREQ MAX1856 2 GND FB PGND REF Idle Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX1856 General Description MAX1856 Wide Input Range, Synchronizable, PWM SLIC Power Supply ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (TA = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C VCC, SYNC/SHDN to GND .....................................-0.3V to +30V PGND to GND .......................................................-0.3V to +0.3V LDO, FREQ, FB, CS to GND.....................................-0.3V to +6V EXT, REF to GND......................................-0.3V to (VLDO + 0.3V) LDO Output Current............................................-1mA to +20mA LDO Short Circuit to GND ...............................................