MAX3325 19-1573 Rev 0 10/99 3V Dual RS-232 Transceiver with LCD Supply and Contrast Controller General Description Features The MAX3325 integrates a two-transmitter, two-receiver +3.0V to +3.6V Single-Supply Operation RS-232 transceiver with an LCD supply plus tempera- Provides 5.0V Regulated Output at 11mA in ture-compensated contrast control. It is intended for 3V Systems small 3V instruments requiring a 5V supply for either 6-Bit DAC with Up/Down Interface for LCD logic or an LCD display, an adjustable bias signal for contrast, LCD temperature compensation, and an Contrast Adjustment RS-232 interface for serial communications. Selectable Positive or Negative LCD Bias The 5V supply is a regulated charge pump followed by Meets EIA-232E Specifications at 250kbps a low-dropout (LDO) linear regulator capable of supply- Guaranteed ing 11mA for the 5V LCD power. 1A Shutdown Mode The MAX3325 has an internal 6-bit digital-to-analog Uses Small 0.22F CapacitorsNo Inductors converter (DAC) providing 64 contrast levels, plus an internal temperature sensor that compensates the Required LCDs contrast for changes in ambient temperature. Temperature Sensor for LCD Contrast The LCD contrast can be designed for any voltage Compensation range from -5V to +2V. Simple, Flexible Design Procedure for a Broad The MAX3325s 250kbps RS-232 transceiver meets all Range of LCD Displays EIA-232E specifications with input voltages from +3.0V to +3.6V. Both the RS-232 section and the LCD supply Ordering Information circuitry can be independently placed in shutdown, tai- loring power consumption for battery-powered equip- PART TEMP. RANGE PIN-PACKAGE ment. The MAX3325 is available in 28-pin SSOP and MAX3325CAI 0C to +70C 28 SSOP narrow DIP packages. MAX3325CNI 0C to +70C 28 Narrow Plastic DIP MAX3325EAI -40C to +85C 28 SSOP MAX3325ENI -40C to +85C 28 Narrow Plastic DIP Pin Configuration Applications PDAs and Palmtop Computers TOP VIEW Handy Terminals C2+ 1 28 C1+ GPS Receivers C2- 2 27 V+ Hand-Held Medical Equipment V- 3 26 V DD Industrial Test Equipment R2IN 4 25 GND R1IN 5 24 C1- MAX3325 R1OUT 6 23 REG R2OUT 7 22 T1OUT V 8 21 T2OUT L LCD 9 20 T1IN TEMP 10 19 T2IN REF- 11 18 SD232 FB 12 17 SDLCD REF+ 13 16 DOWN DAC 14 15 UP Typical Operating Circuit appears at end of data sheet. SSOP/DIP Maxim Integrated Products 1 For free samples & the latest literature: 3V Dual RS-232 Transceiver with LCD Supply and Contrast Controller ABSOLUTE MAXIMUM RATINGS V , V to GND ........................................................-0.3V to +6V Short-Circuit Duration (T OUT, REF+, REF-) .............Continuous DD L LCD, REF-, TEMP to GND .............................-6V to (V + 0.3V) Continuous Output Current DD V+ to GND (Note 1)..................................................-0.3V to +7V REG.................................................................................75mA V- to GND (Note 1) ...................................................+0.3V to -7V LCD.................................................................................40mA V+ to V- (Note 1) ................................................................+13V Continuous Power Dissipation REF+, FB, R OUT to GND ............................-0.3V to (V + 0.3V) 28-Pin SSOP (derate 9.52mW/C above +70C) .........762mW L Input Voltages 28-Pin NDIP (derate 14.3mW/C above +70C) ........1143mW T OUT, SDLCD, SD232, UP, DOWN to GND.......-0.3V to +6V Operating Temperature Range R IN to GND ....................................................................25V MAX3325C I .......................................................0C to +70C Output Voltages MAX3325E I ....................................................-40C to +85C T OUT to GND.................................................................13V Storage Temperature Range .............................-65C to +150C R OUT to GND..........................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10sec) .............................+300C L REG to GND .........................................................-0.3V to +6V Note 1: V+ and V- can have maximum magnitudes of +7V, but their absolute difference cannot exceed 13V. 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 = +3.0V to +3.6V, V = +3.3V, circuit and components of Figure 1, T = T to T , unless otherwise noted. Typical values DD L A MIN MAX are at V = +3.3V, T = +25C.) DD A PARAMETER CONDITIONS MIN TYP MAX UNITS DC CHARACTERISTICS V Supply Current No load, V = V = 3.3V, T = +25C 24 mA DD DD L A V Supply Current No load, V = V = 3.3V, T = +25C 0.5 10 A L DD L A SD232, SDLCD = GND all input pins = GND or V DD V Shutdown Supply Current 0.5 10 A DD V = V = 3.3V T = +25C DD L A DIGITAL-TO-ANALOG CONVERTER Resolution Guaranteed monotonic 6 Bits Full-Scale Voltage No load 1.13 1.2 1.27 V Zero-Scale Voltage No load -15 0 10 mV Output Impedance 0 < V < V +, I 10A 35 50 65 k DAC REF DAC TEMPERATURE SENSOR TEMP Output T = +25C -3.2 V A TEMP Voltage Temperature I < 22A -18 mV/C TEMP Coefficient POSITIVE LINEAR REGULATOR VCC 3.15V, IREG = 0 to 4.7 5 5.3 11mA 1 transmitter loaded with REG Output Voltage V 5k, T = +25C A V 3.0V, I = 0 to CC REG 5 7mA Line Regulation 3V < V < 3.6V 650 mV DD Short-Circuit Current 50 mA NEGATIVE LINEAR REGULATORLCD BIAS Feedback Regulation Point -20 0 20 mV Input Leakage Current (Note 2) V = 0, CMOS input -10 0 10 nA FB LCD Load Regulation (Note 3) V = -4.0V, load = 0 to -3mA 20 mV LCD 2 MAX3325