19-1829; Rev 1; 6/01 KIT ATION EVALU E L B A AVAIL Low-Cost Precision Sensor Signal Conditioner The MAX1452 architecture includes a programmable sensor excitation, a 16-step programmable-gain amplifier (PGA), a 768-byte (6144 bits) internal EEPROM, four 16-bit DACs, an uncommitted op amp, and an onchip temperature sensor. In addition to offset and span compensation. The MAX1452 provides a unique temperature compensation strategy for offset TC and FSOTC that was developed to provide a remarkable degree of flexibility while minimizing testing costs. The MAX1452 is packaged for the commercial, industrial, and automotive temperature ranges in 16-pin SSOP packages. Features ♦ Provides Amplification, Calibration, and Temperature Compensation ♦ Accommodates Sensor Output Sensitivities from 1mV/V to 40mV/V ♦ Single Pin Digital Programming ♦ No External Trim Components Required ♦ 16-Bit Offset and Span Calibration Resolution ♦ Fully Analog Signal Path ♦ On-Chip Lookup Table Supports Multipoint Calibration Temperature Correction ♦ Supports Both Current and Voltage Bridge Excitation ♦ Fast 3.2kHz Frequency Response ♦ On-Chip Uncommitted Op Amp ♦ Secure-Lock™ Prevents Data Corruption ♦ Low 2mA Current Consumption Ordering Information Customization Maxim can customize the MAX1452 for high-volume dedicated applications. Using our dedicated cell library of more than 2000 sensor-specific functional blocks, Maxim can quickly provide a modified MAX1452 solution. Contact Maxim for further information. Applications Pressure Sensors Transducers and Transmitters Strain Gauges Pressure Calibrators and Controllers Resistive Elements Sensors Accelerometers Humidity Sensors Outputs Supported 4–20mA 0 to +5V (Rail-to-Rail®) +0.5V to +4.5V Ratiometric +2.5V to ±2.5V PART TEMP. RANGE 0°C to +70°C 16 SSOP MAX1452EAE -40°C to +85°C 16 SSOP MAX1452AAE -40°C to +125°C 16 SSOP MAX1452C/D 0°C to +70°C Dice* *Dice are tested at TA = +25°C, DC parameters only. A detailed block diagram appears at the end of data sheet. Pin Configuration TOP VIEW ISRC 1 16 FSOTC OUT 2 15 AMP+ VSS 3 14 AMP- INM 4 BDR 5 MAX1452 (NOT TO SCALE) 13 AMPOUT 12 CLK1M INP 6 11 DIO VDD 7 10 UNLOCK TEST 8 Rail-to-Rail is a trademark of Nippon Motorola Ltd. Secure-Lock is a trademark of Maxim Integrated Products. PIN-PACKAGE MAX1452CAE 9 VDDF SSOP ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1452 General Description The MAX1452 is a highly integrated analog-sensor signal processor optimized for industrial and process control applications utilizing resistive element sensors. The MAX1452 provides amplification, calibration, and temperature compensation that enables an overall performance approaching the inherent repeatability of the sensor. The fully analog signal path introduces no quantization noise in the output signal while enabling digitally controlled trimming with the integrated 16-bit DACs. Offset and span are calibrated using 16-bit DACs, allowing sensor products to be truly interchangeable. MAX1452 Low-Cost Precision Sensor Signal Conditioner ABSOLUTE MAXIMUM RATINGS Supply Voltage, VDD to VSS.........................................-0.3V, +6V All Other Pins ...................................(VSS - 0.3V) to (VDD + 0.3V) Short-Circuit Duration, FSOTC, OUT, BDR, AMPOUT .................................................................Continuous Continuous Power Dissipation (TA = +70°C) 16-Pin SSOP (derate 8.00mW/°C above +70°C) ..........640mW Operating Temperature: MAX1452CAE/MAX1452C/D ...............................0°C to +70°C MAX1452EAE ...................................................-40°C to +85°C MAX1452AAE .................................................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature.........................................-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 = +5V, VSS = 0, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.5 5.0 5.5 V GENERAL CHARACTERISTICS Supply Voltage Supply Current Oscillator Frequency VDD IDD (Note 1) fOSC 0.85 2.0 2.5 mA 1 1.15 MHz ANALOG INPUT Input Impedance RIN 1 MΩ ±1 µV/°C Input Referred Offset Tempco (Notes 2, 3) Input Referred Adjustable Offset Range Offset TC = 0 at minimum gain (Note 4) ±150 mV Amplifier Gain Nonlinearity Percent of +4V span, VOUT = +0.5V to 4.5V 0.01 % Common-Mode Rejection Ratio Specified for common-mode voltages between VSS and VDD (Note 2) 90 dB (Note 5) 1-40 mV/V Selectable in 16 steps 39240 V/V CMRR Input Referred Adjustable FSO Range ANALOG OUTPUT Differential Signal-Gain Range Differential Signal Gain Configuration [5:2] 0000bin 34 39 46 Configuration [5:2] 0001bin 47 52 59 Configuration [5:2] 0010bin 58 65 74 Configuration [5:2] 0100bin 82 91 102 Configuration [5:2] 1000bin 133 143 157 Maximum Output Voltage Swing No load from each supply 0.02 Output Voltage Low IOUT = 1mA sinking, TA = TMIN to TMAX 0.100 Output Voltage High IOUT = 1mA sourcing, TA = TMIN to TMAX 4.75 Output Impedance at DC Output Offset Ratio 2 ∆VOUT/ ∆Offset 0.90 V/V V 0.20 V 4.87 V 0.1 Ω 1.05 _______________________________________________________________________________________ 1.20 V/V Low-Cost Precision Sensor Signal Conditioner MAX1452 ELECTRICAL CHARACTERISTICS (continued) (VDD = +5V, VSS = 0, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL Output Offset TC Ratio ∆VOUT/ ∆Offset TC CONDITIONS MIN TYP MAX UNITS 0.9 1 1.2 V/V Step Response and IC (63% Final Value) Maximum Capacitive Load DC to 1kHz (gain = minimum, source impedance = 5kΩ VDDF filter) Output Noise 150 µs 1 µF 0.5 mVRMS BRIDGE DRIVE Bridge Current IBDR Current Mirror Ratio AA VSPAN Range (Span Code) RL = 1.7kΩ 0.1 0.5 2 mA RISOURCE = internal 10 12 14 A/A C000 hex TA = TMIN to TMAX 4000 DIGITAL–TO–ANALOG CONVERTERS DAC Resolution 16 bits ODAC Bit Weight ∆VOUT/ ∆Code DAC reference = VDD = +5.0V 76 µV/bit OTCDAC Bit Weight ∆VOUT/ ∆Code DAC reference = VBDR = +2.5V 38 µV/bit FSODAC Bit Weight ∆VOUT/ ∆Code DAC reference = VDD = +5.0V 76 µV/bit FSOTCDAC Bit Weight ∆VOUT/ ∆Code DAC reference = VBDR = +2.5V 38 µV/bit Including sign 4 bits Input referred, DAC reference = VDD = +5.0V (Note 6) 9 mV/bit COARSE OFFSET DAC IRODAC Resolution IRODAC Bit Weight ∆VOUT/ ∆Code FSOTC BUFFER Minimum Output Voltage Swing No load Maximum Output Voltage Swing No load Current Drive VFSOTC = +2.5V VSS + 0.1 VDD - 1.0 V V -40 +40 µA INTERNAL RESISTORS Current-Source Reference Resistor RISRC 75 kΩ Current-Source Reference Resistor Temperature Coefficient ∆RISRC 1300 ppm/°C RFTC 75 kΩ ∆RFTC 1300 ppm/°C FSOTC Resistor FSOTC Resistor Temperature Coefficient _______________________________________________________________________________________ 3 MAX1452 Low-Cost Precision Sensor Signal Conditioner ELECTRICAL CHARACTERISTICS (continued) (VDD = +5V, VSS = 0, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS TEMPERATURE-TO-DIGITAL CONVERTER Temperature ADC Resolution 8 bits Offset ±3 LSB Gain 1.45 °C/bit Nonlinearity ±0.5 LSB Lowest Digital Output 00 hex Highest Digital Output AF hex UNCOMMITTED OP AMP Open Loop Gain RL = 100kΩ Input Common-Mode Range Output Swing No load, TA = TMIN to TMAX Output Voltage High 1mA source, TA = TMIN to TMAX Output Voltage Low 1mA sink, TA = TMIN to TMAX Offset VIN+ = +2.5V, unity gain buffer Unity Gain Bandwidth 90 dB VSS VDD V VSS + 0.02 VDD 0.02 V 4.85 4.90 0.05 -20 V 0.15 V +20 mV 2 MHz EEPROM Maximum Erase/Write Cycles (Note 7) 10k Cycles Minimum Erase Time (Note 8) 6 ms Excludes sensor or load current. All electronics temperature errors are compensated together with sensors errors. The sensor and the MAX1452 must be at the same temperature during calibration and use. This is the maximum allowable sensor offset. This is the sensor's sensitivity normalized to its drive voltage, assuming a desired full span output of +4V and a bridge voltage of +2.5V. Note 6: Bit weight is ratiometric to VDD. Note 7: Programming of the EEPROM at room temperature is recommended. Note 8: Allow a minimum of 6ms elapsed time before sending any command. Note 1: Note 2: Note 3: Note 4: Note 5: 4 _______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner AMPLIFIER GAIN NONLINEARITY OFFSET DAC DNL OUTPUT ERROR FROM STRAIGHT LINE (mV) DNL (mV) 2.5 0 -2.5 MAX1452 toc02 5.0 MAX1452 toc01 5.0 ODAC = 6800hex OTCDAC = 0 FSODAC = 4000hex FSOTCDAC = 8000hex IRO = 2hex PGA = 0 2.5 0 -2.5 -5.0 -5.0 0 10k 20k 30k 40k 50k 60k -50 70k -25 0 25 50 INPUT VOLTAGE [INP-INM] (mV) OUTPUT NOISE MAX1452 toc03 DAC CODE OUT 10mV/div 400µs/div C = 4.7µF, RLOAD = 1kΩ Pin Description PIN NAME FUNCTION 1 ISRC Bridge Drive Current Mode Setting 2 OUT High ESD and Scan Path Output Signal. May need a 0.1µF capacitor, in noisy environments. OUT may be parallel connected to DIO. 3 VSS Negative Supply Voltage 4 INM Bridge Negative Input. Can be swapped to INP by configuration register. 5 BDR Bridge Drive 6 INP Bridge Positive Input. Can be swapped to INM by configuration register. 7 VDD Positive Supply Voltage. Connect a 0.1µF capacitor from VDD to VSS. 8 TEST Internally Connected. Connect to VSS. _______________________________________________________________________________________ 5 MAX1452 Typical Operating Characteristics (VDD = +5V, TA = +25°C, unless otherwise noted.) Low-Cost Precision Sensor Signal Conditioner MAX1452 Pin Description (continued) PIN NAME FUNCTION 9 VDDF 10 UNLOCK 11 DIO 12 CLK1M 13 AMPOUT 14 AMP- Uncommitted Amplifier Negative Input 15 AMP+ Uncommitted Amplifier Positive Input 16 FSOTC Full Span TC Buffered Output Positive Supply Voltage for EEPROM. Connect a 0.1µF capacitor from VDDF to VSS. Connect VDDF to VDD or for improved noise performance connect a 1kΩ resistor to VDD. Secure-Lock Disable. Allows communication to the device. Digital Input Output. DIO allows communication with the device. 1MHz Clock Output. The clock can be shut off by a configuration bit. Uncommitted Amplifier Output Detailed Description The MAX1452 provides amplification, calibration, and temperature compensation to enable an overall performance approaching the inherent repeatability of the sensor. The fully analog signal-path introduces no quantization noise in the output signal while enabling digitally controlled trimming with the integrated 16-bit DACs. Offset and span can be calibrated to within ±0.02% of span. The MAX1452 architecture includes a programmable sensor excitation, a 16-step programmable-gain amplifier (PGA), a 768-byte (6144 bits) internal EEPROM, four 16-bit DACs, an uncommitted op amp, and an on-chip temperature sensor.The MAX1452 also provides a unique temperature compensation strategy for offset TC and FSOTC that was developed to provide a remarkable degree of flexibility while minimizing testing costs. The customer can select from one to 114 temperature points to compensate their sensor. This allows the latitude to compensate a sensor with a simple first order linear correction or match an unusual temperature curve. Programming up to 114 independent 16-bit EEPROM locations corrects performance in 1.5°C temperature increments over a range of -40°C to +125°C. For sensors that exhibit a characteristic temperature performance, a select number of calibration points can be used with a number of preset values that define the temperature curve. In cases where the sensor is at a different temperature than the ASIC, the MAX1452 uses the sensor bridge itself to provide additional temperature correction. 6 The single pin, serial Digital Input-Output (DIO) communication architecture and the ability to timeshare its activity with the sensor’s output signal enables output sensing and calibration programming on a single line by parallel connecting OUT and DIO. The MAX1452 provides a Secure-Lock feature that allows the customer to prevent modification of sensor coefficients and the 52-byte user definable EEPROM data after the sensor has been calibrated. The Secure-Lock feature also provides a hardware override to enable factory rework and recalibration by assertion of logic high on the UNLOCK pin. The MAX1452 allows complete calibration and sensor verification to be performed at a single test station. Once calibration coefficients have been stored in the ASIC, the customer can choose to retest in order to verify performance as part of a regular QA audit or to generate final test data on individual sensors. The MAX1452’s low current consumption and the integrated uncommitted op amp enables a 4–20mA output signal format in a sensor that is completely powered from a 2-wire current loop. Frequency response can be user-adjusted to values lower than the 3.2kHz bandwidth by using the uncommitted op amp and simple passive components. The MAX1452 (Figure 1) provides an analog amplification path for the sensor signal. It also uses an analog architecture for first-order temperature correction. A digitally controlled analog path is then used for nonlinear temperature correction. Calibration and correction is achieved by varying the offset and gain of a programmable-gain-amplifier (PGA) and by varying the sensor bridge excitation current or voltage. The PGA _______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner VDD BIAS GENERATOR IRO DAC MAX1452 OSCILLATOR CLK1M TEST INP ∑ PGA OUT INM ISRC CURRENT SOURCE ANAMUX A=1 TEMP SENSOR 8-BIT ADC VDDF DIO UNLOCK INTERNAL EEPROM 6144 BITS 16 BIT DAC - FSO (176) POINT 16 BIT DAC - OFFSET (176) 16 BIT DAC - OFFSET TC 16 BIT DAC - FSO TC BDR 416 BITS FOR USER VDD 176 TEMPERATURE LOOK UP POINTS FOR OFFSET AND SPAN. BDR AMP+ FSOTC OP-AMP AMPOUT AMPVSS Figure 1. Functional Diagram utilizes a switched capacitor CMOS technology, with an input referred offset trimming range of more than ±150mV with an approximate 3µV resolution (16 bits). The PGA provides gain values from 39V/V to 240V/V in 16 steps. The MAX1452 uses four 16-bit DACs with calibration coefficients stored by the user in an internal 768 x 8 EEPROM (6144 bits). This memory contains the following information, as 16-bit wide words: • Configuration Register • Offset Calibration Coefficient Table • Offset Temperature Coefficient Register • FSO (Full-Span Output) Calibration Table • FSO Temperature Error Correction Coefficient Register • 52 bytes (416 bits) uncommitted for customer programming of manufacturing data (e.g., serial number and date) Initial offset correction is accomplished at the input stage of the signal gain amplifiers by a coarse offset setting. Final offset correction occurs through the use of a temperature indexed lookup table with 176 16-bit entries. The on-chip temperature sensor provides a unique 16-bit offset trim value from the table with an indexing resolution of approximately 1.5°C from -40°C to +125°C. Every millisecond, the on-chip temperature sensor provides indexing into the offset lookup table in EEPROM and the resulting value transferred to the offset DAC register. The resulting voltage is fed into a summing junction at the PGA output, compensating the sensor offset with a resolution of ±76µV (±0.0019% FSO). If the offset TC DAC is set to zero then the maximum temperature error is equivalent to one degree of temperature drift of the sensor, given the Offset DAC has corrected the sensor at every 1.5°C. The temperature indexing boundaries are outside of the specified Absolute Maximum Ratings. The minimum indexing value is 00hex corresponding to approximately -69°C. All temperatures below this value will output the coefficient value at index 00hex. The maximum indexing value is AFhex, which is the highest lookup table entry. All temperatures higher than approximately 184°C will output the highest lookup table index value. No indexing wrap-around errors are produced. FSO Correction Two functional blocks control the FSO gain calibration. First, a coarse gain is set by digitally selecting the gain of the PGA. Second, FSO DAC sets the sensor bridge current or voltage with the digital input obtained from a temperature-indexed reference to the FSO lookup table in EEPROM. FSO correction occurs through the use of a temperature indexed lookup table with 176 16-bit entries. The on-chip temperature sensor provides a unique FSO trim from the table with an indexing resolution approaching one 16-bit value at every 1.5°C from -40°C to +125°C. The temperature indexing boundaries are outside of the specified Absolute Maximum Ratings. The minimum indexing value is 00hex corresponding to approximately -69°C. All temperatures below this value will output the coefficient value at index 00hex. The maximum indexing value is AFhex, which is the highest lookup table entry. All temperatures higher than approximately 184°C will output the highest lookup table index value. No indexing wraparound errors are produced. Linear and Nonlinear Temperature Compensation Writing 16-bit calibration coefficients into the offset TC and FSOTC registers compensates first-order tempera- _______________________________________________________________________________________ 7 MAX1452 Offset Correction VDD MAX1452 Low-Cost Precision Sensor Signal Conditioner ture errors. The piezoresistive sensor is powered by a current source resulting in a temperature-dependent bridge voltage due to the sensor's temperature resistance coefficient (TCR). The reference inputs of the offset TC DAC and FSOTC DAC are connected to the bridge voltage. The DAC output voltages will track the bridge voltage as it varies with temperature, and by varying the offset TC and FSOTC digital code a portion of the bridge voltage, which is temperature dependent, is used to compensate the first order temperature errors. The internal feedback resistors (RISRC and RSTC) for FSO temperature compensation are optimized to 75kΩ for silicon piezoresistive sensors. However, since the required feedback resistor values are sensor dependent, external resistors may also be used. The internal resistors selection bit in the configuration register selects between internal and external feedback resistors. To calculate the required offset TC and FSOTC compensation coefficients, two test-temperatures are needed. After taking at least two measurements at each temperature, calibration software (in a host computer) calculates the correction coefficients and writes them to the internal EEPROM. For high accuracy applications (errors less than 0.25%), the first-order offset and FSOTC should be compensated with the offset TC and FSOTC DACs, and the residual higher order terms with the lookup table. The offset and FSO compensation DACs provide unique compensation values for approximately 1.5°C of temperature change as the temperature indexes the address pointer through the coefficient lookup table. Changing the offset does not effect the FSO, however changing the FSO will affect the offset due to nature of the bridge. The temperature is measured on both the MAX1452 die and at the bridge sensor. It is recommended to compensate the first-order temperature errors using the bridge sensor temperature. Typical Ratiometric Operating Circuit Ratiometric output configuration provides an output that is proportional to the power supply voltage. This output can then be applied to a ratiometric ADC to produce a digital value independent of supply voltage. Ratiometricity is an important consideration for batteryoperated instruments, automotive, and some industrial applications. The MAX1452 provides a high-performance ratiometric output with a minimum number of external components (Figure 2). These external components include the following: • One supply bypass capacitor. With coefficients ranging from 0000hex to FFFFhex and a +5V reference, each DAC has a resolution of 76µV. Two of the DACs (offset TC and FSOTC) utilize the sensor bridge voltage as a reference. Since the sensor bridge voltage is approximately set to +2.5V the FSOTC and offset TC exhibit a step size of less than 38µV. • One optional output EMI suppression capacitor. • Two optional resistors, RISRC and RSTC, for special sensor bridge types. +5V VDD 7 5 6 VDD 9 BDR VDDF INP OUT 2 OUT MAX1452 16 FSOTC SENSOR 4 INM RSTC ISRC 1 0.1µF TEST VSS 8 0.1µF RISRC 3 GND Figure 2. Basic Ratiometric Output Configuration 8 _______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner MAX1452 G 2N4392 IN 1 S D VPWR +12V TO +40V MAX6105 2 7 5 6 5V VDD GND 3 1kΩ 9 BDR VDDF INP OUT 2 OUT MAX1452 16 FSOTC SENSOR 4 INM RSTC ISRC 1 0.1µF TEST VSS 8 0.1µF 0.1µF 0.1µF RISRC 3 GND Figure 3. Basic Nonratiometric Output Configuration Typical Nonratiometric Operating Circuit (12VDC < VPWR < 40VDC) Nonratiometric output configuration enables the sensor power to vary over a wide range. A high performance voltage reference, such as the MAX6105, is incorporated in the circuit to provide a stable supply and reference for MAX1452 operation. A typical example is shown in Figure 3. Nonratiometric operation is valuable when wide ranges of input voltage are to be expected and the system A/D or readout device does not enable ratiometric operation. Internal Calibration Registers (ICRs) The MAX1452 has five 16-bit internal calibration registers that are loaded from EEPROM, or loaded from the serial digital interface. Data can be loaded into the internal calibration registers under three different circumstances. Normal Operation, Power-On Initialization Sequence • The MAX1452 has been calibrated, the SecureLock byte is set (CL[7:0] = FFhex) and UNLOCK is low. • Power is applied to the device. • The power-on reset functions have completed. Typical 2-Wire, Loop Powered, 4–20mA Operating Circuit • Registers CONFIG, OTCDAC, and FSOTCDAC are refreshed from EEPROM. Process Control systems benefit from a 4–20mA current loop output format for noise immunity, long cable runs, and 2-wire sensor operation. The loop voltages can range from 12VDC to 40VDC and are inherently nonratiometric. The low current consumption of the MAX1452 allows it to operate from loop power with a simple 4–20mA drive circuit efficiently generated using the integrated uncommitted op amp (Figure 4). • Registers ODAC, and FSODAC are refreshed from the temperature indexed EEPROM locations. Normal Operation, Continuous Refresh • The MAX1452 has been calibrated, the SecureLock byte has been set (CL[7:0] = FFhex) and UNLOCK is low. • Power is applied to the device. • The power-on reset functions have completed. • The temperature index timer reaches a 1ms time period. _______________________________________________________________________________________ 9 MAX1452 Low-Cost Precision Sensor Signal Conditioner 2N4392 G VIN+ +12V TO +40V D 100Ω S IN 1 Z1 MAX6105 2 5 6 7 VDD 5VOUT GND 3 1kΩ BDR VDDF INP FSOTC 9 16 0.1µF RSTC MAX1452 SENSOR 4 ISRC 1 INM 0.1µF 0.1µF RISRC 4.99MΩ OUT AMPOUT AMPAMP+ TEST VSS 8 3 2 499kΩ 0.1µF 13 2N2222A 14 15 4.99kΩ 0.1µF 100kΩ 100kΩ 47Ω VIN- Figure 4. Basic 4–20mA Output, Loop-Powered Configuration • • Registers CONFIG, OTCDAC, and FSOTCDAC are refreshed from EEPROM. Registers ODAC and FSODAC are refreshed from the temperature indexed EEPROM locations. Calibration Operation, Registers Updated by Serial Communications • The MAX1452 has not had the Secure-Lock byte set (CL[7:0] = 00hex) or UNLOCK is high. • Power is applied to the device. • The power-on reset functions have completed. • The registers can then be loaded from the serial digital interface by use of serial commands. See the section on Serial I/O and Commands. 10 Internal EEPROM The internal EEPROM is organized as a 768 by 8-bit memory. It is divided into 12 pages, with 64 bytes per page. Each page can be individually erased. The memory structure is arranged as shown in Table 1. The lookup tables for ODAC and FSODAC are also shown, with the respective temp-index pointer. Note that the ODAC table occupies a continuous segment, from address 000hex to address 15Fhex, whereas the FSODAC table is divided in two parts, from 200hex to 2FFhex, and from 1A0hex to 1FFhex. With the exception of the general purpose user bytes, all values are 16-bit wide words formed by two adjacent byte locations (high byte and low byte). The MAX1452 compensates for sensor offset, FSO, and temperature errors by loading the internal calibration registers with the compensation values. These compensation values can be loaded to registers directly via ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner MAX1452 Table 1. EEPROM Memory Address Map PAGE 0 1 2 3 4 5 6 7 8 9 A B LOW-BYTE ADDRESS (hex) HIGH-BYTE ADDRESS (hex) TEMP-INDEX[7:0] (hex) 00 000 001 03E 03F 1F 040 041 20 07E 07F 3F 080 081 40 0BE 0BF 5F 0C0 0C1 60 0FE 0FF 7F 100 101 80 13E 13F 9F 140 141 A0 15E 15F AF to FF 160 161 CONTENTS ODAC Lookup Table Configuration 162 163 Reserved 164 165 OTCDAC 166 167 Reserved 168 169 FSOTCDAC 16A 16B Control Location 16C 16D 17E 17F 180 181 19E 19F 52 General-Purpose User Bytes 1A0 1A1 80 1BE 1BF 8F 1C0 1C1 90 1FE 1FF AF to FF 200 201 00 23E 23F 1F 240 241 20 27E 27F 3F 280 281 40 2BE 2BF 5F 2C0 2C1 60 2FE 2FF 7F the serial digital interface during calibration or loaded automatically from EEPROM at power-on. In this way the device can be tested and configured during calibration and test and the appropriate compensation values stored in internal EEPROM. The device will FSODAC Lookup Table auto-load the registers from EEPROM and be ready for use without further configuration after each power-up. The EEPROM is configured as an 8-bit wide array so each of the 16-bit registers is stored as two 8-bit quantities. The configuration register, FSOTCDAC and OTC- ______________________________________________________________________________________ 11 MAX1452 Low-Cost Precision Sensor Signal Conditioner DAC registers are loaded from the pre-assigned locations in the EEPROM. The ODAC and FSODAC are loaded from the EEPROM lookup tables using an index pointer that is a function of temperature. An ADC converts the integrated temperature sensor to an 8-bit value every 1ms. This digitized value is then transferred into the temp-index register. terminates the baud rate synchronization sequence. This initialization sequence on DIO should occur after a period of 1ms after stable power is applied to the device. This allows time for the power-on reset function to complete and the DIO pin to be configured by Secure-Lock or the UNLOCK pin. Reinitialization Sequence The typical transfer function for the temp-index is as follows: The MAX1452 allows for relearning the baud rate. The reinitialization sequence is one byte transmission of FFhex, as follows. temp-index = 0.69 ✕ Temperature (°C) + 47.58 11111111011111111111111111 where temp-index is truncated to an 8-bit integer value. Typical values for the temp-index register are given in Table 6. When a serial reinitialization sequence is received, the receive logic resets itself to its power-up state and waits for the initialization sequence. The initialization sequence must follow the reinitialization sequence in order to re-establish the baud rate. Note that the EEPROM is byte wide and the registers that are loaded from EEPROM are 16 bits wide. Thus each index value points to two bytes in the EEPROM. Maxim programs all EEPROM locations to FFhex with the exception of the oscillator frequency setting and Secure-Lock byte. OSC[2:0] is in the Configuration Register (Table 3). These bits should be maintained at the factory preset values. Programming 00hex in the Secure-Lock byte (CL[7:0] = 00hex), configures the DIO as an asynchronous serial input for calibration and test purposes. Communication Protocol The DIO serial interface is used for asynchronous serial data communications between the MAX1452 and a host calibration test system or computer. The MAX1452 will automatically detect the baud rate of the host computer when the host transmits the initialization sequence. Baud rates between 4800bps and 38,400bps can be detected and used regardless of the internal oscillator frequency setting. Data format is always 1 start bit, 8 data bits, 1 stop bit and no parity. Communications are only allowed when Secure-Lock is disabled (i.e., CL[7:0] = 00hex) or the UNLOCK pin is held high. Initialization Sequence Sending the initialization sequence shown below enables the MAX1452 to establish the baud rate that initializes the serial port. The initialization sequence is one byte transmission of 01hex, as follows. Serial Interface Command Format All communication commands into the MAX1452 follow a defined format utilizing an interface register set (IRS). The IRS is an 8-bit command that contains both an interface register set data (IRSD) nibble (4-bit) and an interface register set address (IRSA) nibble (4-bit). All internal calibration registers and EEPROM locations are accessed for read and write through this interface register set. The IRS byte command is structured as follows: IRS[7:0] = IRSD[3:0], IRSA[3:0] Where: • IRSA[3:0] is the 4-bit interface register set address and indicates which register receives the data nibble IRSD[3:0]. • IRSA[0] is the first bit on the serial interface after the start bit. • IRSD[3:0] is the 4-bit interface register set data. • IRSD[0] is the fifth bit received on the serial interface after the start bit. The IRS address decoding is shown in Table 9. Special Command Sequences 1111111101000000011111111 A special command register to internal logic (CRIL[3:0]) causes execution of special command sequences within the MAX1452. These command sequences are listed as CRIL command codes as shown in Table 10. The first start bit 0 initiates the baud rate synchronization sequence. The 8 data bits 01hex (LSB first) follow this and then the stop bit, which is indicated above as a 1, A 16-bit write to any of the internal calibration registers is performed as follows: 12 Write Examples ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner DRIVEN BY TESTER DIO 11111 0 1 0 0 11 0 1 0 11 THREE-STATE NEED WEAK PULLUP DRIVEN BY MAX1452 1 1 1 1 1 1 1 1 0 0 0 0 0 1 0 0 0 11 1 1 1 1 1 1 1 11 STOP-BIT MSB LSB START-BIT STOP-BIT MSB LSB START-BIT MAX1452 THREE-STATE NEED WEAK PULLUP Figure 5. DIO Output Data Format 1) Write the 16 data bits to DHR[15:0] using four byte accesses into the interface register set. register designated by IRSP[3:0] are sent out as a byte framed by a start bit and a stop bit. 2) Write the address of the target internal calibration register to ICRA[3:0]. Once the tester finishes sending the RdIRS command, it must three-state its connection to DIO to allow the MAX1452 to drive the DIO line. The MAX1452 will threestate DIO high for 1 byte time and then drive with the start bit in the next bit period followed by the data byte and stop bit. The sequence is shown in Figure 5. The data returned on a RdIRS command depends on the address in IRSP. Table 12 defines what is returned for the various addresses. 3) Write the load internal calibration register (LdICR) command to CRIL[3:0]. When a LdICR command is issued to the CRIL register, the calibration register loaded depends on the address in the internal calibration register address (ICRA). Table 11 specifies which calibration register is decoded. Erasing and Writing the EEPROM The internal EEPROM needs to be erased (bytes set to FFhex) prior to programming the desired contents. Remember to save the 3 MSBs of byte 161hex (highbyte of the configuration register) and restore it when programming its contents to prevent modification of the trimmed oscillator frequency. The internal EEPROM can be entirely erased with the ERASE command, or partially erased with the PageErase command (see Table 10, CRIL command). It is necessary to wait 6ms after issuing the ERASE or PageErase command. After the EEPROM bytes have been erased (value of every byte = FFhex), the user can program its contents, following the procedure below: 1) Write the 8 data bits to DHR[7:0] using two byte accesses into the interface register set. 2) Write the address of the target internal EEPROM location to IEEA[9:0] using three byte accesses into the interface register set. 3) Write the EEPROM write command (EEPW) to CRIL[3:0]. Serial Digital Output When a RdIRS command is written to CRIL[3:0], DIO is configured as a digital output and the contents of the Multiplexed Analog Output When a RdAlg command is written to CRIL[3:0] the analog signal designated by ALOC[3:0] is asserted on the OUT pin. The duration of the analog signal is determined by ATIM[3:0] after which the pin reverts to threestate. While the analog signal is asserted in the OUT pin, DIO is simultaneously three-stated, enabling a parallel wiring of DIO and OUT. When DIO and OUT are connected in parallel, the host computer or calibration system must three-state its connection to DIO after asserting the stop bit. Do not load the OUT line when reading internal signals, such as BDR, FSOTC...etc. The analog output sequence with DIO and OUT is shown in Figure 6. The duration of the analog signal is controlled by ATIM[3:0] as given in Table 13. The analog signal driven onto the OUT pin is determined by the value in the ALOC register. The signals are specified in Table 14. Test System Configuration The MAX1452 is designed to support an automated production test system with integrated calibration and temperature compensation. Figure 7 shows the implementation concept for a low-cost test system capable of testing many transducer modules connected in par- ______________________________________________________________________________________ 13 MAX1452 Low-Cost Precision Sensor Signal Conditioner THREE-STATE NEED WEAK PULLUP DRIVEN BY TESTER DIO 11111 0 1 0 0 11 0 1 0 11 THREE-STATE 2ATIM +1 BYTE TIMES THREE-STATE NEED WEAK PULLUP 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 STOP-BIT MSB LSB START-BIT HIGH IMPEDANCE OUT VALID OUT Figure 6. Analog Output Timing allel. The MAX1452 allows for a high degree of flexibility in system calibration design. This is achieved by use of single-wire digital communication and three-state output nodes. Depending upon specific calibration requirements one may connect all the OUTs in parallel or connect DIO and OUT on each individual module. Sensor Compensation Overview Compensation requires an examination of the sensor performance over the operating pressure and temperature range. Use a minimum of two test pressures (e.g., zero and full-span) and two temperatures. More test pressures and temperatures will result in greater accuracy. A typical compensation procedure can be summarized as follows: Set reference temperature (e.g., 25°C): • Initialize each transducer by loading their respective registers with default coefficients (e.g., based on mean values of offset, FSO and bridge resistance) to prevent overload of the MAX1452. • Set the initial bridge voltage (with the FSODAC) to half of the supply voltage. Measure the bridge voltage using the BDR or OUT pins, or calculate based on measurements. • Calibrate the output offset and FSO of the transducer using the ODAC and FSODAC, respectively. • Store calibration data in the test computer or MAX1452 EEPROM user memory. Set next test temperature: • Calibrate offset and FSO using the ODAC and FSODAC, respectively. • Store calibration data in the test computer or MAX1452 EEPROM user memory. • Calculate the correction coefficients. • Download correction coefficients to EEPROM. • Perform a final test. Sensor Calibration and Compensation Example The MAX1452 temperature compensation design corrects both sensor and IC temperature errors. This enables the MAX1452 to provide temperature compensation approaching the inherent repeatability of the sensor. An example of the MAX1452’s capabilities is shown in Figure 8. A repeatable piezoresistive sensor with an initial offset of 16.4mV and a span of 55.8mV was converted into a compensated transducer (utilizing the piezoresistive sensor with the MAX1452) with an offset of 0.5000V and a span of 4.0000V. Nonlinear sensor offset and FSO temperature errors, which were on the order of 20% to 30% FSO, were reduced to under ±0.1% FSO. The following graphs show the output of the uncompensated sensor and the output of the compensated transducer. Six temperature points were used to obtain this result. MAX1452 Evaluation Kit To expedite the development of MAX1452 based transducers and test systems, Maxim has produced the MAX1452 evaluation kit (EV kit). First-time users of the MAX1452 are strongly encouraged to use this kit. 14 ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner MAX1452 DIO[1:N] DATA DATA VOUT +5V MODULE N MAX1452 MODULE 2 MAX1452 MODULE 1 DION DIO2 DIO1 MAX1452 DIGITAL MULTIPLEXER VDD VSS VOUT VDD VSS VOUT VDD VSS VOUT DVM TEST OVEN Figure 7. Automated Test System Concept The EV kit is designed to facilitate manual programming of the MAX1452 with a sensor. It includes the following: 1) Evaluation Board with or without a silicon pressure sensor, ready for customer evaluation. 3) MAX1452 Communication Software, which enables programming of the MAX1452 from a computer keyboard (IBM compatible), one module at a time. 4) Interface Adapter, which allows the connection of the evaluation board to a PC serial port. 2) Design/Applications Manual, which describes in detail the architecture and functionality of the MAX1452. This manual was developed for test engineers familiar with data acquisition of sensor data and provides sensor compensation algorithms and test procedures. ______________________________________________________________________________________ 15 MAX1452 Low-Cost Precision Sensor Signal Conditioner RAW SENSOR OUTPUT TA = +25°C 30.0 ERROR (% FSO) VOUT (mV) 80 60 40 6 0 UNCOMPENSATED SENSOR TEMPERATURE ERROR FSO OFFSET 20.0 10.0 0.0 -10.0 -20.0 0 20 40 60 80 100 -50 0 4.0 3.0 2.0 1.0 -0.1 -0.15 -50 0 50 100 TEMPERATURE (°C) 150 0 0 20 40 60 PRESSURE (kPs) 80 Figure 8. Comparison of an Uncalibrated Sensor and a Calibrated Transducer Table 2. Registers REGISTER CONFIG ODAC 16 DESCRIPTION Configuration Register Offset DAC Register OTCDAC Offset Temperature Coefficient DAC Register FSODAC Full Span Output DAC Register FSOTCDAC 150 5.0 OFFSET VOUT (V) ERROR (% FSO) FSO 100 COMPENSATED TRANSDUCER TA = +25°C COMPENSATED TRANSDUCER ERROR 0.15 0.1 0.05 0 -0.05 50 TEMPERATURE (°C) PRESSURE (kPs) Full Span Output Temperature Coefficient DAC Register ______________________________________________________________________________________ 100 Low-Cost Precision Sensor Signal Conditioner MAX1452 Table 3. Configuration Register (CONFIG[15:0]) FIELD NAME DESCRIPTION 15:13 OSC[2:0] 12 REXT 11 CLK1M EN 10 PGA Sign Logic ‘1’ inverts INM and INP polarity. 9 IRO Sign Logic ‘1’ for positive input referred offset (IRO). Logic ‘0’ for negative input referred offset (IRO). 8:6 IRO[2:0] Input referred coarse offset adjustment. 5:2 PGA[3:0] Programmable gain amplifier setting. 1 ODAC Sign 0 OTCDAC Sign Oscillator frequency setting. Factory preset, do not change. Logic ‘1’ selects external RISRC and RSTC. Logic ‘1’ enables CLK1M output driver. Logic ‘1’ for positive offset DAC output. Logic ‘0’ for negative offset DAC output. Logic ‘1’ for positive offset TC DAC output. Logic ‘0’ for negative offset TC DAC output. Table 4. Input Referred Offset (IRO[2:0]) IRO SIGN, IRO[2:0] INPUT REFERRED OFFSET CORRECTION AS % OF VDD INPUT REFERRED OFFSET, CORRECTION AT VDD = 5VDC IN mV 1,111 +1.25 +63 1,110 +1.08 +54 1,101 +0.90 +45 1,100 +0.72 +36 1,011 +0.54 +27 1,010 +0.36 +18 1,001 +0.18 +9 1,000 0 0 0,000 0 0 0,001 -0.18 -9 0,010 -0.36 -18 0,011 -0.54 -27 0,100 -0.72 -36 0,101 -0.90 -45 0,110 -1.08 -54 0,111 -1.25 -63 ______________________________________________________________________________________ 17 MAX1452 Low-Cost Precision Sensor Signal Conditioner Table 5. PGA Gain Setting (PGA[3:0]) PGA[3:0] PGA GAIN (V/V) 0000 39 0001 52 0010 65 0011 78 0100 91 0101 104 0110 117 0111 130 1000 143 1001 156 1010 169 1011 182 1100 195 1101 208 1110 221 1111 234 Table 6. Temp-Index Typical Values TEMP-INDEX[7:0] TEMPERATURE (°C) DECIMAL HEXADECIMAL -40 20 14 25 65 41 85 106 6A 125 134 86 Table 7. EEPROM ODAC and FSODAC Lookup Table Memory Map 18 TEMP-INDEX[7:0] EEPROM ADDRESS ODAC LOW BYTE AND HIGH BYTE EEPROM ADDRESS FSODAC LOW BYTE AND HIGH BYTE 00hex to 7Fhex 000hex and 001hex to 0FEhex and 0FFhex 200hex and 201hex to 2FEhex and 2FFhex 80hex to AFhex 100hex and 101hex to 15Ehex and 15Fhex 1A0hex and 1A1hex to 1FEhex and 1FFhex ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner FIELD NAME DESCRIPTION 15:8 CL[15:8] Reserved 7:0 CL[7:0] Control Location. Secure-Lock is activated by setting this to FFhex which disables DIO serial communications and connects OUT to PGA output. Table 9. IRSA Decoding IRSA[3:0] DESCRIPTION 0000 Write IRSD[3:0] to DHR[3:0] (data hold register) 0001 Write IRSD[3:0] to DHR[7:4] (data hold register) 0010 Write IRSD[3:0] to DHR[11:8] (data hold register) 0011 Write IRSD[3:0] to DHR[15:12] (data hold register) 0100 Reserved 0101 Reserved 0110 Write IRSD[3:0] to ICRA[3:0] or IEEA[3:0], (internal calibration register address or internal EEPROM address nibble 0) 0111 Write IRSD[3:0] to IEEA[7:4] (internal EEPROM address, nibble 1) 1000 Write IRSD[3:0] to IRSP[3:0] or IEEA[9:8], (interface register set pointer where IRSP[1:0] is IEEA[9:8]) 1001 Write IRSD[3:0] to CRIL[3:0] (command register to internal logic) 1010 Write IRSD[3:0] to ATIM[3:0] (analog timeout value on read) 1011 Write IRSD[3:0] to ALOC[3:0] (analog location) 1100 to 1110 1111 Reserved Write IRSD[3:0] = 1111bin to relearn the baud rate ______________________________________________________________________________________ 19 MAX1452 Table 8. Control Location (CL[15:0]) MAX1452 Low-Cost Precision Sensor Signal Conditioner Table 10. CRIL Command Codes CRIL[3:0] NAME DESCRIPTION 0000 LdICR Load internal calibration register at address given in ICRA with data from DHR[15:0]. 0001 EEPW EEPROM write of 8 data bits from DHR[7:0] to address location pointed by IEEA [9:0]. 0010 ERASE Erase all of EEPROM (all bytes equal FFhex). 0011 RdICR Read internal calibration register as pointed to by ICRA and load data into DHR[15:0]. 0100 RdEEP Read internal EEPROM location and load data into DHR[7:0] pointed by IEEA [9:0]. 0101 RdIRS Read interface register set pointer IRSP[3:0]. See Table 12. 0110 RdAlg Output the multiplexed analog signal onto OUT. The analog location is specified in ALOC[3:0] (Table 14) and the duration (in byte times) that the signal is asserted onto the pin is specified in ATIM[3:0] (Table 13). 0111 PageErase 1000 to 1111 Reserved Erases the page of the EEPROM as pointed by IEEA[9:6]. There are 64 bytes per page and thus 12 pages in the EEPROM. Reserved. Table 11. IRCA Decode ICRA[3:0] NAME 0000 CONFIG 0001 ODAC 0010 OTCDAC Offset Temperature Coefficient DAC Register 0011 FSODAC Full Scale Output DAC Register 0100 FSOTCDAC 0101 0110 to 1111 20 DESCRIPTION Configuration Register Offset DAC Register Full Scale Output Temperature Coefficient DAC Register Reserved. Do not write to this location (EEPROM test). Reserved. Do not write to this location. ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner MAX1452 Table 12. IRSP Decode IRSP[3:0] RETURNED VALUE 0000 DHR[7:0] 0001 DHR[15:8] 0010 IEEA[7:4], ICRA[3:0] concatenated 0011 CRIL[3:0], IRSP[3:0] concatenated 0100 ALOC[3:0], ATIM[3:0] concatenated 0101 IEEA[7:0] EEPROM address byte 0110 IEED[7:0] EEPROM data byte 0111 TEMP-Index[7:0] 1000 BitClock[7:0] 1001 Reserved. Internal flash test data. 1010-1111 11001010 (CAhex). This can be used to test communication. Table 13. ATIM Definition ATIM[3:0] DURATION OF ANALOG SIGNAL SPECIFIED IN BYTE TIMES (8-BIT TIME) 0000 20 + 1 = 2 byte times i.e. (2 ✕ 8) / baud rate 0001 21 + 1 = 3 byte times 0010 22 + 1 = 5 byte times 0011 23 + 1 = 9 byte times 0100 24 + 1 = 17 byte times 0101 25 + 1 = 33 byte times 0110 26 + 1 = 65 byte times 0111 27 + 1 = 129 byte times 1000 28 + 1 = 257 byte times 1001 29 + 1 = 513 byte times 1010 210 + 1 = 1025 byte times 1011 211 + 1 = 2049 byte times 1100 212 + 1 = 4097 byte times 1101 213 + 1 = 8193 byte times 1110 214 + 1 = 16,385 byte times 1111 In this mode OUT is continuous, however DIO will accept commands after 32,769 byte times. Do not parallel connect DIO to OUT. ______________________________________________________________________________________ 21 MAX1452 Low-Cost Precision Sensor Signal Conditioner Table 14. ALOC Definition ALOC[3:0] ANALOG SIGNAL DESCRIPTION 0000 OUT PGA Output 0001 BDR Bridge Drive 0010 ISRC Bridge Drive Current Setting 0011 VDD Internal Positive Supply 0100 VSS Internal Ground 0101 BIAS5U 0110 AGND 0111 FSODAC 1000 FSOTCDAC 1001 ODAC 1010 OTCDAC 1011 VREF 1100 VPTATP Internal Test Node 1101 VPTATM Internal Test Node 1110 INP Sensor’s Positive Input 1111 INM Sensor’s Negative Input Internal Test Node Internal Analog Ground. Approximately half of VDD. Full Scale Output DAC Full Scale Output TC DAC Offset DAC Offset TC DAC Bandgap Reference Voltage (nominally 1.25V) Table 15. Effects of Compensation TYPICAL UNCOMPENSATED INPUT (SENSOR) TYPICAL COMPENSATED TRANSDUCER OUTPUT Offset…………………..…….…………………………..±100%FSO FSO…………………………….………………………..1 to 40mV/V Offset TC…………………………………………………...20% FSO Offset TC Nonlinearity…..………………………………….4% FSO FSOTC…………………………..………………………..-20% FSO FSOTC Nonlinearity…..……..…………………………….5% FSO Temperature Range..….….……………………..-40°C to +125°C OUT..…….……………………………..Ratiometric to VDD at 5.0V Offset at +25°C……………………………………0.500V ± 200µV FSO at +25°C……………………………………...4.000V ± 200µV Offset accuracy over temp. range….………±4mV (±0.1% FSO) FSO accuracy over temp. range……………±4mV (±0.1% FSO) Chip Information TRANSISTOR COUNT: 67,382 SUBSTRATE CONNECTED TO: VSS 22 ______________________________________________________________________________________ Low-Cost Precision Sensor Signal Conditioner EEPROM (LOOKUP PLUS CONFIGURATION DATA) VDD EEPROM ADDRESS 000H + 001H VDD : 16-BIT FSO DAC ISRC VDD 16-BIT OFFSET DAC RSTC 75kΩ 164H + 165H 166H + 167H 168H + 169H 16AH + 16BH 16CH + 16DH : VSS BDR BANDGAP TEMP SENSOR PHASE REVERSAL MUX VSS TEST CLK1M VDDF FSO DAC LOOKUP TABLE (176 ✕ 16-BITS) 8-BIT LOOKUP ADDRESS ∑∆ FSOTC DAC INP USER STORAGE (52 BYTES) VDD 2FEH + 2FFH VDD ±1 RESERVED FSOTC REGISTER SHADOW CONTROL LOCATION REGISTER 19EH + 19FH 1A0H + 1A1H 16-BIT CONFIGURATION REGISTER SHADOW RESERVED OFFSET TC REGISTER SHADOW : VSS FSOTC OFFSET DAC LOOKUP TABLE (176 ✕ 16-BITS) 15EH + 15FH 160H + 161H 162H + 163H VSS RISRC 75kΩ USAGE UNLOCK VSS DIGITAL INTERFACE VSS DIO FSOTC REGISTER PGA BANDWIDTH ≈ 3kHz ± 10% ∑ MUX ✕ 26 ∑ PGA MUX OUT INM VSS INPUT REFERRED OFFSET (COARSE OFFSET) IRO (3, 2:0) OFFSET mV 1,111 1,110 1,101 1,100 1,011 63 54 45 36 27 1,010 1,001 1,000 0,000 0,001 18 9 0 0 -9 0,010 0,011 0,100 0,101 0,110 0,111 -18 -27 -36 -45 -54 -63 AMPPROGRAMMABLE GAIN STAGE ±1 16-BIT OFFSET TC DAC OTC REGISTER *INPUT REFERRED OFFSET VALUE IS PROPORTIONAL TO VDD. VALUES GIVEN ARE FOR VDD = 5V. VSS PGA (3:0) PGA GAIN TOTAL GAIN 0000 0001 0010 0011 1.5 2.0 39 52 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 65 78 91 104 117 130 143 156 169 182 7.5 8.0 8.5 9.0 195 208 221 234 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 AMPOUT AMP+ UNCOMMITTED OP AMP PARAMETER VALUE VSS TO VDD I/P RANGE I/P OFFSET O/P RANGE NO LOAD 1mA LOAD VSS, VDD ±0.01V VSS, VDD ±0.25V UNITY GBW 10MHz TYPICAL ±20mV PGA BANDWIDTH ≈ 3kHz ± 10% ______________________________________________________________________________________ 23 MAX1452 Detailed Block Diagram Low-Cost Precision Sensor Signal Conditioner SSOP.EPS MAX1452 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. 24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.