MAX1856 19-1898 Rev 0 2/01 Wide Input Range, Synchronizable, PWM SLIC Power Supply General Description Features The MAX1856 offers a low-cost solution for generating a Low-Cost, Off-the-Shelf Transformer SLIC (ringer and off-hook) power supply. Using standard 3V to 28V Input Range off-the-shelf transformers from multiple vendors, the MAX1856 generates various output voltages: -24V and Low Audio-Band Noise on Talk Battery -72V (dual output) for both ringer and off-hook supplies for Effectively Handles Ring Trip Transients voice-enabled broadband consumer premises equipment (CPE), -48V for IP phones and routers, -5V and -15V (sin- Powers 2-, 4-, or 12-Line Equipment gle or dual output) for DSL CO line drivers, or negative High Efficiency Extends Battery Life During voltages as high as -185V for MEMS bias supplies. The output voltages are adjusted with an external voltage Life-Line Support Conditions divider. Adjustable 100kHz to 500kHz Switching Due to its wide operating voltage range, the MAX1856 Frequency operates from a low-cost, unregulated DC power supply Clock Synchronization for cost-sensitive applications like xDSL, cable modems, set-top boxes, LMDS, MMDS, WLL, and FTTH CPE. The Internal Soft-Start MAX1856 provides low audio-band noise for talk battery Current-Mode PWM and Idle Mode Control and a sturdy output capable of handling the ring trip con- Scheme ditions for ring battery. The operating frequency can be set between 100kHz and Logic-Level Shutdown 500kHz with an external resistor in free-running mode. For 10-Pin MAX Package noise-sensitive applications, the MAX1856s operating fre- quency can be synchronized to an external clock over its operating frequency range. The flyback topology allows operation close to 50% duty Ordering Information cycle, offering high transformer utilization, low ripple cur- rent, and less stress on input and output capacitors. PART TEMP. RANGE PIN-PACKAGE Internal soft-start minimizes startup stress on the input MAX1856EUB -40C to +85C 10 MAX capacitor, without any external components. The MAX1856s current-mode control scheme does not require external loop compensation. The low-side current- sense resistor provides accurate current-mode control Typical Operating Circuit and overcurrent protection. Applications INPUT OUT2 3V TO 28V -72V VoIP Ringer and Off-Hook Voltage Generators Cable and DSL Modems 1 2 V CC Set-Top Boxes SYNC/SHDN Wireless Local Loop LDO EXT FTTH 2 OUT1 LMDS/MMDS CS -24V FREQ Routers 2 MAX1856 Industrial Power Supplies GND CO DSL Line Driver Supplies FB MEMS Bias Supplies 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 Maxims website at www.maxim-ic.com.Wide Input Range, Synchronizable, PWM SLIC Power Supply ABSOLUTE MAXIMUM RATINGS V , SYNC/SHDN to GND .....................................-0.3V to +30V Continuous Power Dissipation (T = +70C) CC A PGND to GND .......................................................-0.3V to +0.3V 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW LDO, FREQ, FB, CS to GND.....................................-0.3V to +6V Operating Temperature Range ...........................-40C to +85C EXT, REF to GND......................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C LDO LDO Output Current............................................-1mA to +20mA Storage Temperature Range .............................-65C to +150C LDO Short Circuit to GND ...............................................<100ms Lead Temperature (soldering, 10s) .................................+300C REF Short Circuit to GND...........................................Continuous 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. ELECTRICAL CHARACTERISTICS (V = SYNC/SHDN, V = 5V, V = 5V, R = 200k , T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) CC CC LDO OSC A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS PWM CONTROLLER 328V Operating Input Voltage Range V CC V = V 2.7 5.5 V CC LDO FB Input Current I V = -0.05V 1 50 nA FB FB Load Regulation V = 0 to 100mV for 0 to I 0.013 %/mV CS LOAD(MAX) Line Regulation Typically 0.0074% per % duty factor on EXT 0.0074 %/% Current-Limit Threshold V 85 100 115 mV CS CS Input Current I CS = GND 1 A CS Idle Mode Current-Sense 515 25 mV Threshold V Supply Current (Note 1) I V = -0.05V, V = 3V to 28V 250 400 A CC CC FB CC Shutdown Supply Current SYNC/SHDN = GND, V = 28V 3.5 6 A CC REFERENCE AND LDO REGULATOR 5V V 28V 4.50 5.00 5.50 CC LDO Output Voltage V R = 400 V LDO LDO 3V V 28V 2.65 5.50 CC Undervoltage Lockout V V falling edge, 1% hysteresis (typ) 2.40 2.50 2.60 V UVLO LDO Threshold REF to FB Voltage (Note 2) V R = 10k , C = 0.22F 1.225 1.250 1.275 V REF REF REF REF Load Regulation I = 0 to 400A -2 -10 mV REF REF Undervoltage Lockout Rising edge, 1% hysteresis (typ) 1.0 1.1 1.2 V Threshold OSCILLATOR R = 100k 1% 425 500 575 OSC Oscillator Frequency f R = 200k 1% 225 250 275 kHz OSC OSC R = 500k 1% 85 100 115 OSC R = 100k 1% 86 90 94 OSC Maximum Duty Cycle D % R = 200k 1% 87 90 93 OSC R = 500k 1% 86 90 94 OSC 2 MAX1856