MAX686 19-1327 Rev 1 2/98 DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch General Description Features The MAX686 DAC-controlled boost/inverter IC converts Internal 500mA, 28V N-Channel Switch a positive input voltage to a positive or negative LCD (no external FET required) bias voltage up to +27.5V or -27.5V. The device features Adjustable Output Voltage to +27.5V or -27.5V an internal N-channel MOSFET switch, programmable current limiting, and an internal 6-bit digital-to- 6-Bit DAC-Controlled Output Voltage analog converter (DAC) for digital adjustment of the Up to 90% Efficiency output voltage. It comes in a small 16-pin QSOP pack- age (same size as an 8-pin SO). Small 16-Pin QSOP Package The MAX686 uses a current-limited, pulse-frequency- (Same size as 8-pin SO) modulation (PFM) control scheme to provide high effi- Power-OK Indicator ciency over a wide range of load conditions. Its high switching frequency (up to 300kHz) allows the use of 65A Quiescent Current small external components. 1.5A Shutdown Current An LCDON output allows the LCD bias voltage to be Up to 300kHz Switching Frequency automatically disabled when the display logic voltage is removed, protecting the display. The MAX686 has a +2.7V to +5.5V input voltage range for the IC, and a Ordering Information +0.8V to +27.5V input voltage range for the inductor. PART TEMP. RANGE PIN-PACKAGE Typical quiescent supply current is 65A. Shutdown MAX686C/D 0C to +70C Dice* current is 1.5A. MAX686EEE -40C to +85C 16 QSOP The MAX686 offers high-level integration to save space, reduce power consumption, and increase battery life, *Dice are specified at T = +25C, DC parameters only. A making it an excellent choice for battery-powered portable equipment. The MAX629 is similar to the Functional Diagram appears at end of data sheet. MAX686, except that it does not contain a built-in DAC. Both devices have evaluation kits to facilitate designs. Applications Typical Operating Circuit Positive or Negative LCD Bias Personal Digital Assistants MBR0530L 22H V V = 0.8V TO 27.5V OUT IN Notebook Computers Portable Data-Collection Terminals Palmtop Computers Varactor Tuning Diode Bias R2 V = 2.7V TO 5.5V CC V LX CC R3 0.1F Pin Configuration DACOUT V DD LCDON TOP VIEW PGND 1 16 LX FB UP 2 15 N.C. MAX686 UP R1 DN 3 14 LCDON DAC CONTROL DN POL 4 MAX686 13 GND POK REF V 5 12 V ON/OFF SHDN DD CC ISET 6 11 POK POL ISET 0.1F GND PGND SHDN 7 10 FB DACOUT 9 REF 8 QSOP Maxim Integrated Products 1 For free samples & the latest literature: DAC-Controlled Boost/Inverter LCD Bias Supply with Internal Switch ABSOLUTE MAXIMUM RATINGS Voltage Continuous Power Dissipation (T = +70C) A V , ISET, POK, POL, SHDN, QSOP (derate 8.30mW/C above +70C)......................667mW CC UP, DN, V to GND...........................................-0.3V to +6V Operating Temperature Ranges DD FB, REF, DACOUT to GND.......................-0.3V to (V + 0.3V) MAX686C/D ..........................................................0C to +70C CC PGND to GND .....................................................-0.3V to +0.3V MAX686EEE.......................................................-40C to +85C LX, LCDON to GND..............................................-0.3V to +30V Storage Temperature Range .............................-65C to +160C Current Lead Temperature (soldering, 10sec) .............................+300C LX (sinking) .....................................................................600mA LCDON (sinking)...............................................................10mA 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 = V = V = +5V, C = 0.1F, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) CC DD IN REF A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage (Note 1) V , V 2.7 5.5 V CC DD Input Voltage V Voltage applied to L1 0.8 V V IN OUT Supply Current I + I POL = GND, V = 1.3V, I = 0mA 65 125 A CC DD FB DACOUT Shutdown Current I SHDN = GND 1.3 4 A SHDN V Undervoltage Lockout V Rising or falling 2.10 2.5 2.65 V CC LOCK V Undervoltage Lockout CC 100 mV Hysteresis V DAC Reset Threshold V 0.5 1.5 2.1 V CC RESET Boost configuration, V = 27.5V, OUT Line Regulation 0.1 %/V I = 5mA, V = V = 2.7V to 5.5V LOAD CC DD Boost configuration, V = 27.5V, OUT Load Regulation 0.01 %/mA I = 0mA to 5mA LOAD LX LX Voltage Range V 28 V LX ISET = V 0.42 0.50 0.58 CC LX Switch Current Limit I A LX ISET = GND 0.21 0.25 0.29 V = V = 5V, I = 100mA 0.6 1.2 CC DD LX LX On-Resistance R W LX V = V = 3.3V, I = 100mA 0.8 1.6 CC DD LX LX Leakage Current I V = 28V 1.5 A LXLEAK LX Maximum LX On-Time t 8 10 12 s ON POL = GND, V > 1.2V 0.8 1 1.2 FB POL = V , V < 0.15V 2.8 3.5 4.2 CC FB Minimum LX Off-Time t s OFF POL = GND, V < 0.8V 4 5 6 FB POL = V , V > 0.4V 4 5 6 CC FB 2 MAX686