19-1726; Rev 0; 5/00 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC The MAX1298/MAX1299 implement local and remote temperature sensing with 12-bit resolution, using +5V and +3V supply voltages, respectively. Accuracy is ±1°C from 0 to +70°C, with no calibration needed. The devices feature an algorithmic switched-capacitor analog-to-digital converter (ADC), an on-chip clock, and a 3-wire serial interface compatible with SPI™, QSPI™, and MICROWIRE™. The MAX1298/MAX1299 also perform fully differential voltage measurements with 12-bit resolution and separate track-and-hold (T/H) for positive and negative inputs. Both devices accept versatile input modes consisting of two 3-channel signal pairs, five 1-channel signals relative to a floating common, or VDD/4 relative to ground. An external reference may be used for more accurate voltage measurements. Typical power consumption is only 1.3mW (MAX1299). A shutdown mode and two standby modes provide multiple strategies for prolonging battery life in portable applications that require limited sampling throughput. Features ♦ Local and Remote Temperature Sensing ♦ 12-Bit Resolution for Temperature and Voltage Inputs ♦ ±1°C Accuracy from -40°C to +85°C ♦ Fully Differential Inputs ♦ Single-Supply Operation +4.75V to +5.25V (MAX1298) +2.7V to +3.6V (MAX1299) ♦ 3-Wire SPI/QSPI/MICROWIRE-Compatible Interface ♦ Internal Precision Voltage Reference 2.50V (MAX1298) 1.20V (MAX1299) ♦ Space-Saving 16-Pin SSOP Package Ordering Information The MAX1298/MAX1299 are available in 16-pin SSOP packages. ________________________Applications Temperature/Voltage Supervision of Workstations and Communications Equipment Hand-Held Instruments Medical Equipment Industrial Process Control PART TEMP. SENSE PINACCURACY PACKAGE (°C) TEMP. RANGE MAX1298AEAE -40°C to +85°C 16 SSOP ±0.75 MAX1298BEAE* -40°C to +85°C 16 SSOP ±1.0 MAX1298CEAE -40°C to +85°C MAX1299AEAE -40°C to +85°C 16 SSOP ±4.0 16 SSOP ±0.75 MAX1299BEAE* -40°C to +85°C 16 SSOP ±1.0 MAX1299CEAE -40°C to +85°C 16 SSOP *Future product—contact factory for availability. ±4.0 Pin Configuration TOP VIEW AIN1 1 16 AIN0 SHO 2 15 AIN5 AIN2 3 14 REF AIN3 4 AIN4 5 MAX1298 MAX1299 GND 6 SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp. 12 VDD 11 SCLK 10 DIN SSTRB 7 Typical Operating Circuit appears at end of data sheet. 13 GND 9 CS 8 DOUT SSOP ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX1298/MAX1299 General Description MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC ABSOLUTE MAXIMUM RATINGS VDD to GND.……………………………………………-0.3V to +6V SHO to GND ...............................................-0.3V to (VDD + 0.3V) Analog Inputs to GND (AIN0, AIN1, AIN2, AIN3, AIN4, AIN5, REF).............................................-0.3V to (VDD + 0.3V) Digital Inputs to GND (DIN, SCLK, CS)......-0.3V to (VDD + 0.3V) Digital Outputs to GND (DOUT, SSTRB) ....-0.3V to (VDD + 0.3V) Digital Output Sink Current ..…………………………………25mA Maximum Current into Any Pin……………………………….50mA Continuous Power Dissipation (TA = +70°C) 16-Pin SSOP (derate 8.00mW/°C above +70°C) ........667mW Operating Temperature Range MAX129_ _EAE ...............................................-40°C to +85°C Junction Temperature....……………………………………+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) ....……………………+300°C 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 (VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V (MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY (Note 1) Resolution RES Relative Accuracy (Note 2) INL ±1 LSB Differential Nonlinearity DNL ±1 LSB Offset Error 12 Bits ±2 Inputs AIN0−AIN5 ±10 Offset Temperature Coefficient Gain Error Inputs AIN0−AIN5, offset nulled VDD /4 Absolute Error Gain Temperature Coefficient Channel-to-Channel Offset Matching LSB µV/°C ±4 LSB ±2 LSB ±2 ppm/ °C ±0.5 LSB CONVERSION RATE Conversion Time (Note 3) tCONV Track/Hold Acquisition Time tACQ Aperture Delay tAPR Internal Clock Frequency fCLK Voltage measurement 1.1 Temperature measurement 2.2 µs 16 30 57.6 62.3 ms ns 65.5 kHz -2V REF +2V REF V 0 VDD V 5 µA ANALOG INPUTS (AIN0−AIN5) Input Voltage Range (Note 4) Common-Mode Range Measurement with respect to IN-, Figure 1 Input Current (Note 5) 0.1 Input Capacitance 16 2 _______________________________________________________________________________________ pF 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC (VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V (MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.8 V DIGITAL INPUTS Input Voltage Low VIL Input Voltage High VIH Input Hysteresis VDD - 0.8 VHYST Input Leakage Current V 0.2 IIN V 1 Input Capacitance 16 µA pF V DIGITAL OUTPUTS Output Low Voltage Output High Voltage VOL VOH Three-State Output Leakage Current IOUT ISINK = 5mA ISOURCE = 0.5mA 0.6 V V ±10 µA VDD - 0.6 Three-State Output Capacitance 15 pF POWER REQUIREMENTS Positive Supply Voltage Positive Supply Current (Note 6) VDD IDD MAX1298 4.75 5.25 MAX1299 2.7 3.6 Full-on, voltage measurements, internal reference MAX1298 390 MAX1299 350 Full-on, voltage measurements, external reference MAX1298 310 MAX1299 280 Full-on, temperature measurements, internal reference Full-on, temperature measurements, external reference MAX1298 440 500 MAX1299 400 500 MAX1298 360 MAX1299 330 120 190 2 Standby, SCLK = GND Standby-plus, SCLK = GND Shutdown, SCLK = GND Power-Supply Rejection Ratio PSRR (Note 7) INTERNAL VOLTAGE REFERENCE CHARACTERISTICS VDD = 5V Reference Voltage VREF VDD = 3V Reference Tempco 65 MAX1298 2.494 2.50 2.506 MAX1299 1.197 1.20 1.203 REF Line Regulation REF Load Regulation 0 to 100µA output current (Note 8) mA µF 0.1 fN = 10Hz to 10kHz V ppm/°C 1.25 Capacitive Bypass at REF REF Output Noise dB ±20 Output Short-Circuit Current µA 10 50 TC VREF V MAX1298 130 MAX1299 65 µVRMS MAX1298 +3.0 MAX1299 +0.2 MAX1298 4 10 MAX1299 2 10 mV/V µV/µA _______________________________________________________________________________________ 3 MAX1298/MAX1299 ELECTRICAL CHARACTERISTICS (continued) MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC ELECTRICAL CHARACTERISTICS (continued) (VDD = 4.75V to 5.25V (MAX1298), VDD = +2.7V to 3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V (MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL EXTERNAL VOLTAGE REFERENCE CHARACTERISTICS MAX1298 Reference Voltage Range VREF MAX1299 REF Input Resistance CONDITIONS MIN TYP 0.8 2.5 0.8 1.2 Converting 10 Shutdown 25 REF Input Capacitance MAX UNITS V MΩ 24 pF INTERNAL TEMPERATURE MEASUREMENT CHARACTERISTICS Resolution TA = +85°C, P D = 1mW TA = 0°C to +70°C Output Error (Notes 1, 9) TA = -40°C to 0°C, TA = +70°C to +85°C Power-Supply Rejection Ratio °C 0.13 PSRR (Note 7) Noise MAX129_A ±0.75 MAX129_B ±1 MAX129_C MAX129_A ±0.75 MAX129_B ±1 ±1 MAX129_C ±2 MAX129_A ±0.75 MAX129_B ±1 °C ±4 MAX129_C 0.2 °C/V 0.18 °CRMS EXTERNAL TEMPERATURE MEASUREMENT CHARACTERISTICS Output Error 2N3904 (Note 10) ±2 ±4 °C Remote Diode Excitation (1X) 10 µA Remote Diode Excitation (10X) 100 µA 4 _______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC (VDD = +4.75V to 5.25V (MAX1298), VDD = +2.7V to +3.6V (MAX1299), external reference, VREF = +2.5V (MAX1298), VREF = +1.2V (MAX1299), fSCLK = 2.5MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Figures 4, 6) PARAMETER SCLK Frequency SYMBOL fSCLK CONDITIONS MIN TYP MAX 2.5 UNITS MHz SCLK Pulse Width Low tCL 200 ns SCLK Pulse Width High tCH 200 ns CS Low to SCLK High tCSS 100 ns SCLK High to CS Setup tCSH 100 ns CS Pulse Width tCS 100 ns SCLK High to CS Low Setup tCS0 50 ns SCLK High to CS High Setup tCS1 100 ns DIN Setup to SCLK High Time tDS 100 ns DIN Hold Time tDH 0 SCLK Fall to Output Data Valid tDO RL = 100kΩ, CL = 50pF 150 ns CS Fall to Output Enable tDV RL = 100kΩ, CL = 50pF 150 ns CS Rise to Output Disable tTR RL = 100kΩ, CL = 50pF 50 SSTRB Rise to SCLK Rise tSCLK SCLK Fall to SSTRB Fall tSSTRB ns 0 ns ns 200 ns Note 1: Tested at VDD = +5.0V (MAX1298) and VDD = +3.0V (MAX1299). Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has been calibrated. Note 3: Conversion time is defined as the number of clock cycles (64 for voltage measurements, 125 for temperature measurements) multiplied by the internal clock period. Note 4: Individual analog input voltages cannot extend beyond the power-supply rails. Note 5: Input resistance is typically 250MΩ; 5µA limit reflects limitations in production testing. Note 6: Specifications for full-on status assume continuous conversions. Power modes are software selected (Table 4). Note 7: Measured at VFS(+4.75V) - VFS(+5.25V) for the MAX1298 and at VFS(+2.7V) - VFS(+3.6V) for the MAX1299. Note 8: External load should not change during conversions for specified accuracy. Note 9: Excludes noise and self-heating effects. Output error for MAX129_C guaranteed by design. Note 10: External temperature sensing over -40°C to +85°C range, device at +25°C. Guaranteed by design. _______________________________________________________________________________________ 5 MAX1298/MAX1299 TIMING CHARACTERISTICS Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX1299 INTEGRAL NONLINEARITY vs. OUTPUT CODE 0.4 0.2 0 -0.2 -0.4 -0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -1.0 -2500 -1.0 -2500 -1250 0 1250 2500 1.0 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1250 0 1250 -1.0 -2500 2500 -1250 0 1250 2500 OUTPUT CODE OUTPUT CODE OUTPUT CODE MAX1299 DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE MAX1298 SUPPLY CURRENT vs. SUPPLY VOLTAGE (VOLTAGE MEASUREMENT MODE) MAX1299 SUPPLY CURRENT vs. SUPPLY VOLTAGE (VOLTAGE MEASUREMENT MODE) 450 0.2 0 -0.2 -0.4 350 450 400 SUPPLY CURRENT (µA) 0.4 INTERNAL REFERENCE 400 SUPPLY CURRENT (µA) 0.6 500 EXTERNAL REFERENCE 300 250 200 150 250 200 150 100 -0.8 50 50 0 1250 0 4.7 2500 EXTERNAL REFERENCE 300 100 0 INTERNAL REFERENCE 350 -0.6 -1250 MAX1298/9-06 500 MAX1298/9-05 0.8 -1.0 -2500 MAX1298/9-03 0.6 -0.8 MAX1298/9-04 4.8 4.9 5.0 5.1 5.2 2.7 2.9 3.1 3.3 3.5 OUTPUT CODE SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) MAX1298 SUPPLY CURRENT vs. SUPPLY VOLTAGE (TEMPERATURE MEASUREMENT MODE) MAX1299 SUPPLY CURRENT vs. SUPPLY VOLTAGE (TEMPERATURE MEASUREMENT MODE) MAX1298 SUPPLY CURRENT vs. TEMPERATURE (VOLTAGE MEASUREMENT MODE) 350 EXTERNAL REFERENCE 300 250 200 150 INTERNAL REFERENCE 400 SUPPLY CURRENT (µA) INTERNAL REFERENCE 450 EXTERNAL REFERENCE 350 500 300 250 200 150 450 350 250 200 150 100 50 50 50 0 0 4.9 5.0 5.1 SUPPLY VOLTAGE (V) 5.2 EXTERNAL REFERENCE 300 100 4.8 INTERNAL REFERENCE 400 100 4.7 MAX1298/9-09 450 400 500 MAX1298/9-07 500 SUPPLY CURRENT (µA) DIFFERENTIAL NONLINEARITY (LSB) 0.8 -0.8 1.0 6 MAX1298/9-02 0.6 1.0 MAX1298/9-08 INTEGRAL NONLINEARITY (LSB) 0.8 INTEGRAL NONLINEARITY (LSB) MAX1298/9-01 1.0 MAX1298 DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE DIFFERENTIAL NONLINEARITY (LSB) MAX1298 INTEGRAL NONLINEARITY vs. OUTPUT CODE SUPPLY CURRENT (µA) MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC 0 2.7 2.9 3.1 3.3 SUPPLY VOLTAGE (V) 3.5 -40 -20 0 20 40 TEMPERATURE (°C) _______________________________________________________________________________________ 60 80 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC 350 EXTERNAL REFERENCE 300 250 200 150 EXTERNAL REFERENCE 300 250 200 150 300 250 200 150 50 50 50 0 0 0 20 40 60 80 -40 -20 0 20 40 60 -40 80 -20 0 20 40 60 80 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) MAX1298 POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX1299 POWER-DOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX1298 POWER-DOWN SUPPLY CURRENT vs. TEMPERATURE 350 300 250 STANDBY+ 200 150 STANDBY 500 350 300 250 200 STANDBY+ 150 STANDBY 450 400 350 300 250 150 100 100 50 50 50 0 0 4.9 5.0 5.1 5.2 STANDBY+ 200 100 4.8 MAX1298/9-15 400 SUPPLY CURRENT (µA) 400 450 SUPPLY CURRENT (µA) 450 MAX1298/9-14 500 MAX1298/9-13 500 STANDBY 0 2.7 2.9 3.1 3.3 3.5 -40 -20 0 20 40 60 80 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) TEMPERATURE (°C) MAX1299 POWER-DOWN SUPPLY CURRENT vs. TEMPERATURE MAX1298 INTERNAL REFERENCE VOLTAGE vs. SUPPLY VOLTAGE MAX1299 INTERNAL REFERENCE VOLTAGE vs. SUPPLY VOLTAGE REFERENCE VOLTAGE (V) 400 350 300 250 200 STANDBY+ 150 STANDBY 100 1.22 REFERENCE VOLTAGE (V) 450 2.51 2.50 2.49 MAX1298/9-18 2.52 MAX1298/9-16 500 MAX1298/9-17 4.7 EXTERNAL REFERENCE 350 100 -20 INTERNAL REFERENCE 400 100 -40 SUPPLY CURRENT (µA) 350 450 100 0 SUPPLY CURRENT (µA) INTERNAL REFERENCE 400 SUPPLY CURRENT (µA) INTERNAL REFERENCE 450 SUPPLY CURRENT (µA) 400 500 MAX1298/9-11 450 SUPPLY CURRENT (µA) 500 MAX1298/9-10 500 MAX1299 SUPPLY CURRENT vs. TEMPERATURE (TEMPERATURE MEASUREMENT MODE) MAX1298 SUPPLY CURRENT vs. TEMPERATURE (TEMPERATURE MEASUREMENT MODE) MAX1298/9-12 MAX1299 SUPPLY CURRENT vs. TEMPERATURE (VOLTAGE MEASUREMENT MODE) 1.21 1.20 1.19 50 0 2.48 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 1.18 4.7 4.8 4.9 5.0 5.1 SUPPLY VOLTAGE (V) 5.2 2.7 2.9 3.1 3.3 3.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 7 MAX1298/MAX1299 Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX1298 INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE MAX1299 INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE 2.51 2.50 2.49 2.48 -20 0 20 40 60 1.20 1.19 80 -40 -20 0 20 40 60 80 TEMPERATURE (°C) TEMPERATURE (°C) MAX1298 OFFSET vs. SUPPLY VOLTAGE MAX1299 OFFSET vs. SUPPLY VOLTAGE MAX1298/9-22 1.0 MAX1298/9-21 1.0 0.5 OFFSET (LSB) 0.5 0 0 -0.5 -0.5 -1.0 -1.0 4.7 4.8 4.9 5.0 5.1 2.7 5.2 2.9 3.1 3.3 3.5 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) MAX1298 OFFSET vs. TEMPERATURE MAX1299 OFFSET vs. TEMPERATURE 1.0 MAX1298/9-23 1.0 0.5 OFFSET (LSB) 0.5 MAX1298/9-24 OFFSET (LSB) 1.21 1.18 -40 0 -0.5 0 -0.5 -1.0 -1.0 -40 -20 0 20 40 TEMPERATURE (°C) 8 MAX1298/9-20 MAX1298/9-19 1.22 REFERENCE VOLTAGE (V) REFERENCE VOLTAGE (V) 2.52 OFFSET (LSB) MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC 60 80 -40 -20 0 20 40 60 TEMPERATURE (°C) _______________________________________________________________________________________ 80 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC (TA = +25°C, unless otherwise noted.) MAX1298 GAIN ERROR vs. TEMPERATURE MAX1299 GAIN ERROR vs. TEMPERATURE 0.5 GAIN ERROR (LSB) 0 -0.5 -0.5 -1.0 -1.0 -40 -20 0 20 40 60 80 -20 0 20 40 60 80 TEMPERATURE (°C) MAX1298 TEMPERATURE ERROR vs. INTERNAL DIODE TEMPERATURE MAX1299 TEMPERATURE ERROR vs. INTERNAL DIODE TEMPERATURE 0.5 0 -0.5 -1.0 MAX1298/9-30 MAX1298/9-29 1.0 TEMPERATURE ERROR (°C) TEMPERATURE ERROR (°C) -40 TEMPERATURE (°C) 1.0 0.5 0 -0.5 -1.0 -60 -40 -20 0 20 40 60 80 100 -60 -40 -20 0 20 40 60 80 TEMPERATURE (°C) TEMPERATURE (°C) MAX1298 TEMPERATURE ERROR vs. REMOTE DIODE TEMPERATURE MAX1299 TEMPERATURE ERROR vs. REMOTE DIODE TEMPERATURE 2.0 MAX1298/9-31 2.0 1.5 TEMPERATURE ERROR (°C) 1.5 TEMPERATURE ERROR (°C) 0 1.0 0.5 0 -0.5 -1.0 100 MAX1298/9-32 GAIN ERROR (LSB) 0.5 MAX1298/9-28 1.0 MAX1298/9-27 1.0 1.0 0.5 0 -0.5 -1.0 -1.5 -1.5 -2.0 -2.0 -60 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 100 -60 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) _______________________________________________________________________________________ 9 MAX1298/MAX1299 Typical Operating Characteristics (continued) 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC MAX1298/MAX1299 Pin Description 10 PIN NAME FUNCTION 1 AIN1 Analog Input 1. Negative differential input relative to AIN0 or positive differential input relative to AIN5 (Table 5). Connect to the cathode of external diode 1 for remote temperature sensing. 2 SHO Shield Output. Used to suppress leakage currents at the anodes of remote temperature sensors (see Remote Diode Shielding). May also be connected to the shield of twisted-pair input cables used for remote temperature measurements. Leave unconnected for other applications. 3 AIN2 Analog Input 2. Positive differential input relative to AIN3 or positive differential input relative to AIN5 (Table 5). Connect to the anode of external diode 2 for remote temperature sensing. 4 AIN3 Analog Input 3. Negative differential input relative to AIN2 or positive differential input relative to AIN5 (Table 5). Connect to the cathode of external diode 2 for remote temperature sensing. 5 AIN4 Analog input 4. Positive differential input relative to AIN5 (Table 5). 6 GND Ground. Connect to pin 13. 7 SSTRB 8 CS 9 DOUT 10 DIN Serial Data Input. DIN latches data on the rising edge of SCLK. 11 SCLK Serial Clock Input. Clocks data in and out of the serial interface. 12 VDD Positive Supply Voltage. Bypass with a 0.1µF capacitor to GND (pin 13). 13 GND Ground (star ground) 14 REF Reference-Buffer Output/ADC Reference Input. Reference voltage for A/D conversion. Bypass to GND (pin 13) with a 0.1µF capacitor. Select reference mode by writing to configuration byte (Table 2). 15 AIN5 Analog Input 5. Negative differential input relative to AIN0–AIN4 (Table 5). 16 AIN0 Analog Input 0. Positive differential input relative to AIN1 or positive differential input relative to AIN5 (Table 5). Connect to the anode of external diode 1 for remote temperature sensing. Serial Strobe Output. SSTRB goes low at the beginning of an A/D conversion, and it goes high when the conversion is finished. Active-Low Chip Select. Data will not be clocked into DIN unless CS is low. When CS is high, DOUT is at high impedance. Serial Data Output. DOUT transitions on the falling edge of SCLK. ______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC MAX1298/MAX1299 CS SCLK INPUT REGISTER DIN OUTPUT REGISTER MAX1298 MAX1299 DIODE BIAS CONTROL DOUT CONTROL LOGIC CLOCK AIN0 AIN1 IN+ T/H AIN2 AIN3 INPUT MUX 12-BIT ADC AIN4 AIN5 IN- T/H VDD GND SHIELD OUTPUT VDD/4 SHO REF REF Figure 1. Functional Diagram Detailed Description The MAX1298/MAX1299 are low-power, serial-output, multichannel ADCs with temperature-sensing capability for thermostatic, process-control, and monitoring applications. An algorithmic switched-capacitor converter with T/H circuitry for both positive and negative inputs supports fully differential 12-bit conversions from an internal temperature sensor, two external temperature sensors, or voltage sources in a variety of channel con- figurations. Microprocessor (µP) control is made easy through a flexible 3-wire serial interface. Figure 1 shows a simplified functional diagram of the internal architecture for the MAX1298/MAX1299. In temperature-sensing mode, the multiplexer (mux) steers bias currents through internal or external diodes while the ADC computes their temperature in relation to changes in forward voltage. Channels not used for temperature measurement can be configured to measure other system voltages. ______________________________________________________________________________________________________ 11 MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC TIMING/CONTROL LOGIC RIN 40k IN+ T/H CHOLDP 4pF FULLY DIFFERENTIAL A/D OUTPUT RIN 40k INT/H CHOLDN 4pF TRACK AND HOLD RR 30k REF CREF 4pF GAIN OF 2 Figure 2. Converter Input Structure Converter Operation Figure 2 shows a simplified model of the converter input structure. Once initiated, a voltage conversion requires 64 fCLK periods, where fCLK is the internal master clock. Each conversion is preceded by 13 fCLK periods of warm-up time, performed in twelve 4 fCLK period cycles, and followed by 3 fCLK periods to load the output register. SSTRB falls at the beginning of a conversion and rises at the end of a conversion. Inputs IN+ and IN- charge capacitors CHOLDP and CHOLDN, respectively, during the acquisition interval that occurs during the first fCLK period of the first conversion cycle. In the second f CLK period, the T/H switches open so that charge is retained on CHOLDP and CHOLDN as a sample of the differential voltage between IN+ and IN-. This charge is transferred to the ADC during the third and fourth fCLK periods. The reference sampling process begins in the second conversion cycle and continues until the conversion is complete. Sampling occurs during the second and fourth fCLK periods to yield an effective doubling of the reference voltage. The reference sampling requirement 12 is signal dependent and may or may not occur in every subsequent conversion cycle. Temperature conversion is essentially nothing more than subtracting the results of two sequential voltage conversions. The only difference is that output registers are not loaded at the end of the first conversion. Thus, temperature conversions require 2 x 64 - 3 = 125 fCLK periods. Figures 3a and 3b show timing diagrams for voltage and temperature conversions, respectively. Track/Hold The T/H stage for the MAX1298/MAX1299 is a simple switched-capacitor sampling operation. The time required for the T/H stage to acquire an input signal is a function of how fast its input capacitance is charged. If the signal source impedance is high, the acquisition time lengthens and more time must be allowed between conversions. The acquisition time (tACQ) is the maximum time the device takes to acquire the signal. Calculate this with the following equation: tACQ = 7 (Rs + RIN) CIN where Rs is the source impedance of the input signal, RIN is the T/H input impedance (40kΩ), and CIN is the ______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC MAX1298/MAX1299 SSTRB FCLK 13 fCLKs WARMUP 3 fCLKs WRITE TO OUTPUT REGISTER REF ACQUISITION 1 REF ACQUISITION 2 44 fCLKs INPUT ACQUISITION fCLKs CONVERSION CYCLE 1 CONVERSION CYCLES 2–12 REFERENCE SAMPLING Figure 3a. Voltage Conversion Timing Diagram SSTRB FCLK 13 fCLKs WARMUP INPUT ACQUISITION 4 fCLKs CONVERSION CYCLE 1 44 fCLKs CONVERTION CYCLES 2–12 REFERENCE SAMPLING FIRST CONVERSION 13 fCLKs WARMUP 3 fCLKs SUBTRACTION AND WRITE TO OUTPUT REGISTER INPUT ACQUISITION 48 fCLKs CONVERTION CYCLES 1–12 SECOND CONVERSION Figure 3b. Temperature Conversion Timing Diagram input sampling capacitance of the ADC (4pF). Source impedances below 100kΩ have no significant effect on MAX1298/MAX1299 AC performance. Analog Input Protection Internal protection diodes clamp the analog inputs to VDD and GND, so channels can swing within GND 0.3V and VDD + 0.3V without damage. However, for accurate conversions, the inputs should not extend beyond the supply rails. If an off-channel analog input extends beyond the supply rails, limit the input current to 2mA. Serial Digital Interface The MAX1298/MAX1299 feature a serial interface that is fully compatible with SPI, QSPI, and MICROWIRE devices. For SPI/QSPI, ensure that the CPU serial interface runs in master mode so it generates the serial clock signal. Select a 2.5MHz clock frequency or less, and set zero values for clock polarity (CPOL) and phase (CPHA) in the µP control registers. Figure 4 shows detailed serial interface timing information. See Tables 2–5 for programming information. ______________________________________________________________________________________ 13 MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC CS t CS t CSS t CSO t CH t CS1 t CSH SCLK t DH t CL t DS X DIN VALID X t DV VALID t DO VALID X t TR DOUT Figure 4. Detailed Serial Interface Timing Output Data Format Output data from the MAX1298/MAX1299 are clocked onto DOUT on the falling edge of SCLK in the form of two 8-bit words, MSB first (Table 1). For temperature conversions, the output is 12-bit binary (D10–S0) padded with 2 leading extraneous bits and two trailing zeros. For voltage conversions, the output is 12-bit two’s-complement binary (D11–D0) with 1 sub-bit and two trailing zeros. Figure 5 shows the bipolar transfer function. OUTPUT CODE 011111111111 011111111110 000000000010 000000000001 000000000000 111111111111 111111111110 111111111101 +FS = + 2VREF -FS = - 2VREF 1LSB = 2VREF 2048 Performing a Conversion 100000000010 100000000001 - FS + 1LSB 0 + FS - 1LSB IN+ - IN - (LSB) Figure 5. Bipolar Transfer Function Input Data Format Input data (configuration and conversion bytes) are clocked into the MAX1298/MAX1299 at DIN on the rising edge of SCLK when CS is low. The start bit (MSB) of an input data byte is the first logic 1 bit that arrives: After CS falls, OR after receipt of a complete configuration byte with no conversion in progress, OR after 16 bits have been clocked onto DOUT following a conversion. 14 On power-up, the MAX1298/MAX1299 defaults to shutdown mode. Start a conversion by transferring a configuration byte and a conversion byte into DIN with the control formats shown in Tables 2 and 3, respectively. (See Power Modes for related discussion.) SSTRB goes low on the falling edge of the last bit of the conversion byte, and it returns high when the conversion is complete. For best noise performance, SCLK should remain low while SSTRB is low. Typical conversion times are 2.2ms for temperature measurements and 1.1ms for voltage measurements. The MSB of the 2 output bytes is present at DOUT starting at the rising edge of SSTRB. Successive SCLK falling edges shift the two 8-bit data bytes out from an internal register. Additional (>16) SCLK edges will result in zeros on DOUT. SSTRB does not go into a high-impedance state when CS goes high. Pulling CS high prevents data from being clocked in or out, but it does not adversely affect a conversion in progress. Figure 6 shows SSTRB timing details. Subsequent conversions with the same reference mode do not require a configuration byte. ______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC D11 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 S0 0 0 Table 2. Configuration-Byte Format BIT 7 (MSB) BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 (LSB) Start 0 0 0 0 PM1 PM0 REF BIT NAME 7 (MSB) Start DESCRIPTION First logic 1 after CS goes low. (See Input Data Format.) 6, 5, 4, 3 Must be 0000 to load a configuration byte. 2, 1 PM1, PM0 0 REF These 2 bits select the desired power mode (Table 4). A logic high enables the internal reference. A logic low disables the internal reference and selects the external reference mode. Table 3. Conversion-Byte Format BIT 7 (MSB) Start BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 0 1 0 SEL3 SEL2 SEL1 BIT NAME 7 (MSB) Start DESCRIPTION First logic 1 after CS goes low. (See Input Data Format.) 6, 5, 4 3, 2, 1, 0 Must be 010 to load a conversion byte. SEL3, SEL2, SEL1, SEL0 These 4 bits select the input configuration (Table 5). CSB t CSH SSTRB BIT 0 (LSB) SEL0 t CSS t SCK t CONV t SSTRB SCLK t DO PDO CLOCKED IN DOUT SSTRB TIMING Figure 6. Detailed SSTRB Timing Reference Selection Select between internal and external voltage modes through bit REF of the configuration byte. Set REF = 1 for internal reference mode and REF = 0 for external reference mode. Internal Reference The MAX1298 has a 2.50V internal reference, while the MAX1299 has a 1.20V internal reference. Both are factory trimmed for accuracy. When internal reference is selected, REF can be used to drive an external load with 100µA capability. Bypass REF to GND with a 0.1µF (min) capacitance. Wake-up time is C x 2.5 x 104s for the MAX1298 and C x 1.2 x 104s for the MAX1299. External Reference The MAX1298 can directly accept reference voltages at REF from 0.8V to 2.5V, while the MAX1299 can directly accept reference voltages from 0.8V to 1.2V. Bypass REF to GND with a 0.1µF capacitor. Temperature measurements always use internal reference. Power Modes The MAX1298 (MAX1299) typically requires supply currents of 380µA (350µA) or 310µA (280µA) when performing voltage conversions at 100% duty cycle with internal or external references, respectively. The differ- ______________________________________________________________________________________ 15 MAX1298/MAX1299 Table 1. Output Data Format MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC ence reflects the power requirement of an internal reference buffer amplifier that can accommodate external loads. Temperature conversions at 100% duty cycle increase supply currents to 440µA (400µA) through additional amplification, buffer, and bias circuitry that is otherwise inactive. Place the MAX1298/MAX1299 in a low-current powerdown state between conversions to conserve power. Select standby, standby-plus, or shutdown through bits PM1 and PM0 of the initialization byte (Table 4). The MAX1298/MAX1299 assume the shutdown power mode when VDD is first applied. Standby Mode Standby mode turns off the MAX1298/MAX1299 ADC, internal clock, and reference buffer amplifier. Special circuitry for temperature conversions is also deactivated. Wake-up time is limited by the reference buffer amplifier and the associated bypass capacitor (see Internal Reference). When an external reference is used, wake-up time is 0.1ms. Standby-Plus Mode Standby-plus mode is similar to the standby mode, but the internal reference output buffer remains active to shorten the wake-up time to 0.1ms for internal reference mode. When using an external reference, standby-plus mode is equivalent to standby mode. Table 4. Power-Mode Selection PM1 0 PM0 0 0 1 MODE Shutdown Standby-plus 1 0 Standby 1 1 Normal operation achieve a digital output that is proportional to absolute temperature in degrees Kelvin. The reference voltage used in conjunction with temperature measurements is derived from the internal reference source to ensure that 1LSB corresponds to 1/8 of a degree. To convert to degrees Celsius, subtract 273.15 from the temperature inferred from the ADC output. Temperature measurements require a conversion time of 2.2ms. Shield Output Buffer The MAX1298/MAX1299 provide a shield output buffer voltage at SHO that is approximately 0.6V (one diode drop) above V DD /2. When performing temperature measurements with an external diode, use this voltage to suppress error-producing leakage currents (see Remote Diode Shielding). Figure 7 shows the SHO output circuit. Shutdown Mode Shutdown mode turns off all functions other than startup circuitry, thereby reducing typical supply current to 2µA. Data registers are cleared. Use this power mode when interconversion times are no less than 5ms. 5µA SHO Monitoring VDD This mode of operation samples and converts the supply voltage, VDD/4, which is internally generated. The reference voltage must be larger than VDD/8 for the operation to work properly. From the result of a conversion (CODE), CODE = 256 VDD / VREF. VDD 2 Figure 7. SHO Output Circuit Temperature Measurements The MAX1298/MAX1299 perform temperature measurements with internal or external diode-connected transistors through a three-step process. First, the diode bias current changes from 31.6µA to 10µA to produce a temperature-dependent bias voltage difference, which is amplified by a factor of 20 and converted to digital format. Second, the bias current changes from 31.6µA to 100µA, and the bias voltage difference is similarly amplified by a factor of 20 and converted to digital format. Third, the intermediate results are subtracted to 16 Applications Information Remote Diode Selection Temperature accuracy depends on having a goodquality, diode-connected small-signal transistor. Accuracy has been experimentally verified for 2N3904 devices. CPUs and other ICs having on-board temperature-sensing diodes can also be monitored if the diode connections are floating. ______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC MAX1298/MAX1299 Table 5. Input Selection SEL3 SEL2 SEL1 SEL0 POSITIVE INPUT (IN+) NEGATIVE INPUT (IN-) 0 0 0 0 AIN0 AIN5 0 0 0 1 AIN1 AIN5 0 0 1 0 AIN2 AIN5 0 0 1 1 AIN3 AIN5 0 1 0 0 AIN4 AIN5 0 1 0 1 — — 0 1 1 0 AIN5 AIN5 0 1 1 1 Internal diode anode* Internal diode cathode 1 0 0 0 AIN0 AIN1 1 0 0 1 AIN2 AIN3 1 0 1 0 — — 1 VDD/4 GND 1 0 1 1 1 0 0 External diode 1 anode* (AIN0) External diode 1 cathode (AIN1) 1 1 0 1 External diode 2 anode* (AIN2) External diode 2 cathode (AIN3) 1 1 1 0 — — 1 1 1 1 — — *Temperature-measurement mode Table 6. Remote-Sensor Transistor Manufacturer MANUFACTURER MODEL NUMBER Central Semiconductor (USA) CMPT3904 Fairchild Semiconductor (USA) MMBT3904 Motorola (USA) MMBT3904 Rohm Semiconductor (Japan) SST3904 Siemens (Germany) SMB3904 Zetex (England) FMMT3904CT-ND The transistor must be a small-signal type with a base resistance less than 100Ω. Tight specifications for forward current gain (+50 to +150, for example) indicate that the manufacturer has good process controls and that the devices have consistent Vbe characteristics. (See Table 6 for recommended devices.) For heatsink mounting, the 500-32BT02-000 thermal sensor from Fenwal Electronics is a good choice. This device consists of a diode-connected transistor, an aluminum plate with screw hole, and twisted-pair cable (Fenwal Inc., Milford MA, 508-478-6000). Twisted-Pair and Shielded Cables For remote-sensor distances greater than 8 inches, or in particularly noisy environments, use a twisted pair. A practical length is 6 to 12 feet. For longer distances, the best solution is a shielded twisted pair such as that used for audio microphones. For example, the Belden 8451 works well for distances up to 100 feet in a noisy environment. Connect the shield to SHO. Cable resistances affect remote-sensor accuracy; 1Ω series resistance introduces +0.004°C error. Remote Diode Shielding Temperature measurements will reflect significant error if a portion of the bias current supplied to the diode anode is allowed to flow through parallel paths to ground. If the diode-connected transistor is mounted on a PC board, suppress error-producing “leakage” current by surrounding the collector/base leads with a metal trace that is connected to the SHO shield output (Figure 8). ______________________________________________________________________________________ 17 MAX1298/MAX1299 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC SHIELD ANODE between the endpoints of the transfer function, once offset and gain errors have been nullified. The static linearity parameters for the MAX1298/MAX1299 are measured using the best-straight-line-fit method. Differential Nonlinearity (DNL) Differential nonlinearity is the difference between an actual step width and the ideal value of 1LSB. A DNL error specification of less than 1LSB guarantees no missing codes and a monotonic transfer function. Offset Error The offset error is the difference between the ideal and the actual offset points. For an ADC, the offset point is the midstep value when the digital output is zero. Gain Error CATHODE Figure 8. Remote Diode Shielding for PC Boards Layout, Grounding, and Bypassing For best performance, use PC boards. Do not use wirewrap boards. Board layout should ensure that digital and analog signal lines are separated from each other. Do not run analog and digital (especially clock) signals parallel to one another or run digital lines underneath the ADC package. High-frequency noise in the VDD power supply may affect ADC performance. Bypass the supply with a 0.1µF capacitor close to pin VDD. Minimize capacitor lead lengths for best supply-noise rejection. If the power supply is very noisy, connect a 10Ω resistor in series with the supply to provide lowpass filtering. The gain or full-scale error is the difference between the ideal and actual gain points on the transfer function, after the offset error has been canceled out. For an ADC, the gain point is the midstep value when the digital output is full scale. Aperture Delay Aperture delay (tAD) is the time defined between the rising edge of the sampling clock and the instant when an actual sample is taken. Chip Information TRANSISTOR COUNT: 13,669 PROCESS: BiCMOS Definitions Relative Accuracy Relative accuracy is the deviation of the values on an actual transfer function from a straight line. This straight line can be either a best-straight-line fit or a line drawn 18 ______________________________________________________________________________________ 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC 0.1µF +5V VDD AIN0 AIN1 2N3904 2N3904 CS MAX1298 (SHIELD) AIN2 SCLK AIN3 DIN SHO DOUT AIN4 SSTRB AIN5 GND GND ______________________________________________________________________________________ 19 MAX1298/MAX1299 Typical Operating Circuit 12-Bit Serial-Output Temperature Sensors with 5-Channel ADC SSOP.EPS MAX1298/MAX1299 Package Information Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.