MAX6691 19-2304 Rev 1 2/07 Four-Channel Thermistor Temperature-to-Pulse- Width Converter General Description Features The MAX6691 four-channel thermistor temperature-to- Simple Single-Wire Interface pulse-width converter measures the temperatures of up Measures Up to Four Thermistor Temperatures to four thermistors and converts them to a series of out- Low-Average Thermistor Current Minimizes Self- put pulses whose widths are related to the thermistors temperatures. Each of the four thermistors and an Heating Errors external fixed resistor (R ) form a voltage-divider that EXT Internal Voltage Reference Isolates Thermistor is driven by the MAX6691s internal voltage reference from Power-Supply Noise (V ). V and the voltage across R are mea- REF REF EXT Accommodates Any Thermistor Temperature sured and converted to a pulse. Range The MAX6691 has a single open-drain I/O pin that can be readily connected to a variety of microcontrollers. The microcontroller initiates a conversion by pulling the I/O pin low and releasing it. When conversion is done, the MAX6691 signals the end of conversion by pulling the I/O pin low once again. The pulse corresponding to the first thermistor is sent immediately after the release of the I/O pin. The on-chip power-management circuitry reduces the average thermistor current to minimize errors due to thermistor self-heating. Between conversions, the Ordering Information MAX6691 falls into a 10A (max) sleep mode, where PIN- PKG the voltage reference is disabled and the supply cur- PART TEMP RANGE PACKAGE CODE rent is at its minimum. MAX6691MUB -55C to +125C 10 MAX U10-2 The MAX6691 is available in a 10-pin MAX package and is specified from -55C to +125C temperature range. Applications HVAC Home Appliances Medical Devices Pin Configuration Typical Application Circuit V CC TOP VIEW TOP VIEW 10k V CC T1 1 10 T1 1 10 V CC I/O T2 MICRO- 2 9 T2 2 9 I/O CONTROLLER T1 T3 MAX6691 3 8 N.C. T3 3 8 N.C. T2 MAX6691 T4 GND 4 7 T4 4 7 GND T3 R- R+ 5 6 R- 5 6 R+ T4 R EXT MAX Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.Four-Channel Thermistor Temperature-to-Pulse- Width Converter ABSOLUTE MAXIMUM RATINGS V to GND...........................................................-0.3V to +6.0V Operating Temperature Range .........................-55C to +125C CC All Other Pins to GND.................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C CC I/O, R+, R-, T1T4 Current................................................20mA Storage Temperature Range .............................-65C to +150C ESD Protection (Human Body Model) .............................2000V Lead Temperature (soldering, 10s) .................................+300C Continuous Power Dissipation (T = +70C) A 10-Pin MAX (derate 5.6mW/C above +70C) ........444.4mW 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 5.5V, T = -55C to +125C, unless otherwise noted. Typical values are specified at V = 3.3V and T = +25C.) (Note1) CC A CC A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS T = +25C, V = 3.3V 0.5 A CC T /T Accuracy V % FS HIGH LOW REXT T = T to T 1.0 A MIN MAX Supply Voltage Range V 3.0 5.5 V CC Supply Current I During conversion, no load 300 600 A CC Sleep-Mode Supply Current I 3.5 10 A STANDBY Input Leakage Current I 1.0 A LEAKAGE Reference Voltage Output V I = 1mA, T = +25C 1.19 1.24 1.32 V REF REF A Reference Load Regulation 0 < I < 2mA 0.1 0.2 % REF Reference Supply Rejection 0.2 % 0.3 Logic Input Low Voltage V V IL V CC 0.7 Logic Input High Voltage V V IH V CC TIMING CHARACTERISTICS (V = 3.0V to 5.5V, T = -55C to +125C, unless otherwise noted. Typical values are specified at V = 3.3V and T = +25C.) CC A CC A (Figure 1) (Note1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Glitch Immunity on I/O Input 500 ns Conversion Time t 86 102 156 ms CONV Nominal Pulse Width t 4.0 4.9 7.5 ms LOW Start Pulse Width t 5s START Data Ready Pulse Width t 103 122 188 s READY Error Pulse Width t 103 122 188 s ERROR Rise Time t C = 15pF, R = 10k 600 ns RISE L L Fall Time t C = 15pF, R = 10k 600 ns FALL L L Note 1: Specification limits over temperature are guaranteed by design, not production tested. 2 MAX6691