19-3268; Rev 2; 3/05 4-Channel, 10-Bit, System Monitors with Programmable Trip Window and SMBus Alert Response Applications System Monitoring/Supervision Servers/Workstations High Reliability Power Supplies Medical Instrumentation Features ♦ Monitor Mode Programmable Lower/Upper Trip Threshold Alarm-Status Register Records Fault Events SMBus Alert Response Programmable Sampling Intervals ♦ 10-Bit I2C-Compatible ADC ±1 LSB INL, ±1 LSB DNL ♦ 4-Channel Single-Ended or 2-Channel Fully Differential Inputs ♦ Software Programmable Bipolar/Unipolar Conversions ♦ Fast Sampling Rate 94.4ksps While Continuously Reading Conversions 150ksps in Monitor Mode ♦ High-Speed I2C-Compatible Serial Interface 100kHz/400kHz Standard/Fast Mode Up to 1.7MHz High-Speed Mode 6 Available I2C Slave Addresses ♦ Single Supply 2.7V to 3.6V (MAX1361) 4.5V to 5.5V (MAX1362) ♦ Internal Reference 2.048V (MAX1361) 4.096V (MAX1362) ♦ External Reference: 1V to VDD ♦ Low Power 436µA in Monitor Mode (150ksps) 670µA at 94.4ksps 6µA at 1ksps 0.5µA in Power-Down Mode ♦ Small Package 10-Pin µMAX SMBus is a trademark of Intel Corporation. I2C is a trademark of Philips Corporation. Purchase of I2C components from Maxim Integrated Products, Inc. or one of its sublicensed Associated Companies, conveys a license under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. AutoShutdown is a trademark of Maxim Integrated Products, Inc. µMAX is a registered trademark of Maxim Integrated Products, Inc. Typical Operating Circuit and Pin Configuration appear at end of data sheet. Ordering Information/Selector Guide PART I2C SLAVE ADDRESS SUPPLY VOLTAGE (V) 10 µMAX 0110100/0110101 2.7 to 3.6 10 µMAX 0110010/0110011 2.7 to 3.6 0110110/0110111 2.7 to 3.6 TEMP RANGE PIN-PACKAGE MAX1361EUB -40°C to +85°C MAX1361LEUB* -40°C to +85°C MAX1361MEUB -40°C to +85°C 10 µMAX *Future product—contact factory for availability. Ordering Information/Selector Guide continued at end of data sheet. ________________________________________________________________ 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 MAX1361/MAX1362 General Description The MAX1361/MAX1362 low-power, 10-bit, 4-channel, analog-to-digital converters (ADCs) feature a digitally programmable window comparator with an interrupt output for automatic system-monitoring applications. Once configured, monitor mode automatically asserts an interrupt when any analog input exceeds the programmed upper or lower thresholds, without interaction to the host. The MAX1361/MAX1362 respond to the SMBus™ alert, allowing quick identification of the alarming device on a shared interrupt. A programmable delay between monitoring intervals lowers power consumption at reduced monitoring rates. In addition, the MAX1361/MAX1362 integrate an internal voltage reference, a clock, and a 1.7MHz, highspeed, I2C™-compatible, 2-wire, serial interface. The optimized interface allows a maximum conversion rate of 94.4ksps in normal mode while reading back the conversion results. Each of the four analog inputs is configurable for single-ended or fully differential operation and unipolar or bipolar operation. Two scan modes utilize on-chip random access memory (RAM) to allow eight conversions of a selected channel or scanning of a group of channels to reduce interface overhead. These devices operate from a single 2.7V to 3.6V (MAX1361) or 4.5V to 5.5V (MAX1362) supply and require only 436µA at the maximum sampling rate of 150ksps in monitor mode and 670µA at the maximum sampling rate of 94.4ksps. AutoShutdown™ powers down the devices between conversions, reducing supply current to less than 0.5µA when idle. The full-scale analog-input range is determined by the internal reference or by an externally applied reference voltage ranging from 1V to VDD. The MAX1361 features a 2.048V internal reference, and the MAX1362 features a 4.096V internal reference. The MAX1361/MAX1362 are available in a 10-pin µMAX® package and are specified over the extended (-40°C to +85°C) temperature range. For 12-bit applications, refer to the pin-compatible MAX1363/MAX1364 data sheet. MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V AIN0–AIN3, A0, REF to GND......................-0.3V to (VDD + 0.3V) SDA, SCL, INT to GND .............................................-0.3V to +6V Maximum Current Into Any Pin .........................................±50mA Continuous Power Dissipation (TA = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) ........444.4mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-60°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 = 2.7V to 3.6V (MAX1361), VDD = 4.5V to 5.5V (MAX1362), VREF = 2.048V (MAX1361), VREF = 4.096V (MAX1362), CREF = 0.1µF, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY (fSAMPLE = 94.4ksps) (Note 1) Resolution 10 Bits Relative Accuracy INL (Note 2) ±1 LSB Differential Nonlinearity DNL No missing codes ±1 LSB ±1 LSB Offset Error Offset-Error Temperature Coefficient Relative to FSR Gain Error (Note 3) Gain Temperature Coefficient Relative to FSR 0.3 ppm/°C ±1 LSB 0.3 ppm/°C Channel-to-Channel Offset Matching ±0.1 LSB Channel-to-Channel Gain Matching ±0.1 LSB DYNAMIC PERFORMANCE (fIN(SINE-WAVE) = 10kHz, VIN(P-P) = VREF, fSAMPLE = 94.4ksps) Signal-to-Noise Plus Distortion SINAD 60 dB Up to the 5th harmonic -70 dB 70 dB Full-Power Bandwidth SINAD > 57dB 3.0 MHz Full-Linear Bandwidth -3dB point 5.0 MHz Total Harmonic Distortion THD Spurious-Free Dynamic Range SFDR CONVERSION RATE Conversion Time (Note 4) tCONV Throughput Rate (Note 5) fSAMPLE Internal clock External clock Internal clock, SCAN[1:0] = 01 2 6.8 10.6 µs 53 External clock 94.4 Monitor mode, SCAN[1:0] = 10 150 _______________________________________________________________________________________ ksps 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response (VDD = 2.7V to 3.6V (MAX1361), VDD = 4.5V to 5.5V (MAX1362), VREF = 2.048V (MAX1361), VREF = 4.096V (MAX1362), CREF = 0.1µF, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS Track/Hold Acquisition Time MIN Internal Clock Frequency Aperture Delay (Note 6) TYP MAX 800 ns 2.8 tAD UNITS External clock, fast mode 60 External clock, high-speed mode 30 MHz ns ANALOG INPUT (AIN0–AIN3) Unipolar Input Voltage Range, SingleEnded and Differential (Note 7) Input Multiplexer Leakage Current Input Capacitance 0 VREF -VREF / 2 Bipolar ON/OFF leakage current, VAIN_ = 0 or VDD +VREF / 2 ±0.01 CIN ±1 22 V µA pF INTERNAL REFERENCE (Note 8) Reference Voltage VREF Reference-Voltage Temperature Coefficient TA = +25°C MAX1361 2.027 2.048 2.068 MAX1362 4.055 4.096 4.137 25 TCVREF REF Short-Circuit Current ppm/°C 2 REF Source Impedance V 1.5 mA kΩ EXTERNAL REFERENCE REF Input Voltage Range VREF (Note 9) REF Input Current IREF fSAMPLE = 94.4ksps 1 VDD V 40 µA DIGITAL INPUTS/OUTPUTS (SCL, SDA, A0) Input High Voltage VIH Input Low Voltage VIL Input Hysteresis 0.7 x VDD 0.1 x VDD VHYST Input Current IIN Input Capacitance CIN Output Low Voltage VOL V 0.3 x VDD V V ±10 15 µA pF ISINK = 3mA 0.4 V Output Low Voltage ISINK = 3mA 0.4 V INT Leakage Current No faults detected INT OUTPUT ±10 Output Capacitance 15 µA pF POWER REQUIREMENTS Supply Voltage VDD MAX1361 2.7 3.6 MAX1362 4.5 5.5 V _______________________________________________________________________________________ 3 MAX1361/MAX1362 ELECTRICAL CHARACTERISTICS (continued) MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response ELECTRICAL CHARACTERISTICS (continued) (VDD = 2.7V to 3.6V (MAX1361), VDD = 4.5V to 5.5V (MAX1362), VREF = 2.048V (MAX1361), VREF = 4.096V (MAX1362), CREF = 0.1µF, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS fSAMPLE = 150ksps, monitor mode (Note 10) fSAMPLE = 94.4ksps, external clock MAX1361 fSAMPLE = 40ksps, internal clock fSAMPLE = 10ksps, internal clock fSAMPLE = 1ksps, internal clock Supply Current IDD fSAMPLE = 150ksps, monitor mode (Note10) fSAMPLE = 94.4ksps, external clock MAX1362 fSAMPLE = 40ksps, internal clock fSAMPLE = 10ksps, internal clock fSAMPLE = 1ksps, internal clock Shutdown Current Power-Supply Rejection Ratio PSRR TYP MAX Internal MIN 660 1600 External reference 436 1350 Internal 900 1150 External reference 670 900 Internal 530 External reference 230 Internal 380 External reference 60 Internal 330 External reference UNITS 6 Internal 666 1600 External reference 436 1350 Internal 900 1150 External reference 670 900 Internal 530 External reference 230 Internal 380 External reference 60 Internal 330 External reference µA 6 Internal reference on 330 Internal reference off 0.5 10 ±0.01 ±0.5 LSB/V 400 kHz Full-scale input (Note 11) µA TIMING CHARACTERISTICS FOR FAST MODE (Figures 1a, 2) Serial Clock Frequency fSCL Bus Free Time Between a STOP (P) and a START (S) Condition tBUF 4 1.3 _______________________________________________________________________________________ µs 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response (VDD = 2.7V to 3.6V (MAX1361), VDD = 4.5V to 5.5V (MAX1362), VREF = 2.048V (MAX1361), VREF = 4.096V (MAX1362), CREF = 0.1µF, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Hold Time for START (S) Condition Low Period of the SCL Clock SYMBOL CONDITIONS MIN TYP MAX UNITS tHD, STA 0.6 µs tLOW 1.3 µs tHIGH 0.6 µs Setup Time for a Repeated START Condition (Sr) tSU, STA 0.6 µs Data Hold Time tHD, DAT 0 Data Setup Time tSU, DAT 100 High Period of the SCL Clock 900 ns ns Rise Time of Both SDA and SCL Signals, Receiving tR Measured from 0.3VDD to 0.7VDD 0 300 ns Fall Time of SDA Transmitting tF Measured from 0.3VDD to 0.7VDD 0 300 ns Setup Time for STOP (P) Condition Capacitive Load for Each Bus Line tSU, STO 0.6 CB Pulse Width of Spike Suppressed µs 400 pF 50 ns 1.7 MHz TIMING CHARACTERISTICS FOR HIGH-SPEED MODE (CB = 400pF, Figures 1a, 2) (Note 12) Serial Clock Frequency Hold Time, Repeated START Condition (Sr) fSCLH (Note 13) tHD, STA 160 (Note 13) ns Low Period of the SCL Clock tLOW 320 ns High Period of the SCL Clock tHIGH 120 ns Setup Time for a Repeated START Condition (Sr) tSU, STA 160 ns Data Hold Time tHD, DAT Data Setup Time tSU, DAT (Note 14) 0 150 10 ns ns Rise Time of SCL Signal tRCL Measured from 0.3VDD to 0.7VDD 20 80 ns Rise Time of SCL Signal After Acknowledge Bit tRCL1 Measured from 0.3VDD to 0.7VDD 20 160 ns Fall Time of SCL Signal tFCL Measured from 0.3VDD to 0.7VDD 20 80 ns Rise Time of SDA Signal tRDA Measured from 0.3VDD to 0.7VDD 20 160 ns Fall Time of SDA Signal tFDA Measured from 0.3VDD to 0.7VDD 20 160 ns Setup Time for STOP (P) Condition Capacitive Load for Each Bus Pulse Width of Spike Suppressed tSU, STO 160 CB 0 ns 400 pF 10 ns _______________________________________________________________________________________ 5 MAX1361/MAX1362 ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VDD = 2.7V to 3.6V (MAX1361), VDD = 4.5V to 5.5V (MAX1362), VREF = 2.048V (MAX1361), VREF = 4.096V (MAX1362), CREF = 0.1µF, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) Note 1: Devices configured for unipolar single-ended inputs. Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the gain and offset have been calibrated. Note 3: Offset nulled. Note 4: Conversion time is defined as the number of clock cycles needed for conversion multiplied by the clock period. Conversion time does not include acquisition time. SCL is the conversion clock in the external clock mode. Note 5: The throughput rate of the I2C bus is limited to 94.4ksps. The MAX1361/MAX1362 can perform conversions up to 150ksps in monitor mode when not reading back results on the I2C bus. Note 6: A filter on the SDA and SCL inputs suppresses noise spikes and delays the sampling instant. Note 7: The absolute input voltage range for the analog inputs (AIN0–AIN3) is from GND to VDD. Note 8: When the internal reference is configured to be available at AIN3/REF (SEL[2:1] = 11), decouple AIN3/REF to GND with a 0.01µF capacitor. Note 9: ADC performance is limited by the converter’s noise floor, typically 300µVP-P. Note 10: Maximum conversion throughput in internal clock mode when the data is not clocked out. Note 11: For the MAX1361, PSRR is measured as N V (3.6V) − V (2.7V) × 2 − 1 FS FS VREF (3.6V − 2.7V) [ ] and for the MAX1362, PSRR is measured as N V (5.5V) − V (4.5V) × 2 − 1 FS FS VREF (5.5V − 4.5V) Note 12: CB = total capacitance of one bus line in pF. Note 13: fSCLH must meet the minimum clock low time plus the rise/fall times. Note 14: A master device must provide a data hold time for SDA (referred to VIL of SCL) to bridge the undefined region of SCL’s falling edge. [ ] Typical Operating Characteristics (VDD = 3.3V (MAX1361), VDD = 5V (MAX1362), fSCL = 1.7MHz, external clock, fSAMPLE = 94.4ksps, single-ended, unipolar, TA = +25°C, unless otherwise noted.) INTEGRAL NONLINEARITY vs. DIGITAL CODE 0.4 0.3 -0.1 AMPLITUDE (dBc) INL (LSB) 0 0.1 0 -0.1 -0.2 200 400 600 800 DIGITAL OUTPUT CODE 6 1000 -100 -160 -0.5 0 -80 -140 -0.4 -0.3 -60 -120 -0.3 -0.2 fSAMPLE = 94.4ksps fIN = 10kHz -20 -40 0.2 0.1 0 MAX1361 toc02 0.2 FFT PLOT 0.5 MAX1361 toc01 0.3 MAX1361 toc03 DIFFERENTIAL NONLINEARITY vs. DIGITAL CODE DNL (LSB) MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response 0 200 400 600 800 DIGITAL OUTPUT CODE 1000 0 10 20 30 FREQUENCY (kHz) _______________________________________________________________________________________ 40 50 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response 550 EXTERNAL REFERENCE 500 0.45 0.40 0.4 0.3 MAX1362 0.2 450 400 EXTERNAL REFERENCE 0 300 -40 -25 -10 5 20 35 50 65 0.20 MAX1361 0.15 0 3.2 2.7 80 3.7 4.2 4.7 -40 -25 -10 5.2 5 20 35 50 65 80 TEMPERATURE (°C) INPUT VOLTAGE (V) TEMPERATURE (°C) AVERAGE SUPPLY CURRENT vs. CONVERSION RATE (EXTERNAL CLOCK) INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE NORMALIZED REFERENCE VOLTAGE vs. SUPPLY VOLTAGE B NORMALIZED TO REFERENCE VALUE AT +25°C 1.0006 MAX1362 1.0004 1.0002 1.0000 0.9998 0.9996 MAX1361 1.00004 1.00002 1.00000 0.99998 0.99992 0.9990 -10 5 20 35 50 65 80 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 TEMPERATURE (°C) CONVERSION RATE (ksps) -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.3 0.9 0.8 GAIN ERROR (LSB) OFFSET ERROR (LSB) -0.2 GAIN ERROR vs. TEMPERATURE 1.0 MAX1361 toc11 0 MAX1361 toc10 -0.1 VDD (V) OFFSET ERROR vs. SUPPLY VOLTAGE OFFSET ERROR vs. TEMPERATURE 0 -0.4 -0.5 -0.6 0.7 0.6 0.5 0.4 -0.7 0.3 -0.8 -0.8 0.2 -0.9 -0.9 0.1 -1.0 -1.0 -0.7 -40 -25 -10 5 20 35 50 TEMPERATURE (°C) MAX1361 NORMALIZED TO REFERENCE VALUE AT VDD = 3.3V 0.99990 -40 -25 10 20 30 40 50 60 70 80 90 100 1.00006 0.99994 0.9992 MAX1362 NORMALIZED TO REFERENCE VALUE AT VDD = 5V 1.00008 0.99996 0.9994 0 1.00010 65 80 MAX1361 toc09 1.0008 MAX1361 toc08 A 1.0010 VREF NORMALIZED A) INTERNAL REFERENCE ALWAYS ON B) EXTERNAL REFERENCE MAX1361 toc07 800 750 700 650 600 550 500 450 400 350 300 250 200 VREF NORMALIZED AVERAGE IDD (µA) 0.25 0.05 350 OFFSET ERROR (LSB) 0.30 0.10 0.1 MAX1361 MAX1362 0.35 MAX1361 toc12 SUPPLY CURRENT (µA) 600 0.5 MAX1361 toc06 INTERNAL REFERENCE SETUP BYTE EXT REF: 10111010 INT REF: 11011010 MAX1361 650 SDA = SCL = VDD SUPPLY CURRENT (µA) MAX1362 0.50 MAX1361 toc05 INTERNAL REFERENCE 700 0.6 IDD (µA) 750 MAX1361 toc04 800 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. TEMPERATURE 0 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 VDD (V) -40 -25 -10 5 20 35 50 65 80 TEMPERATURE (°C) _______________________________________________________________________________________ 7 MAX1361/MAX1362 Typical Operating Characteristics (continued) (VDD = 3.3V (MAX1361), VDD = 5V (MAX1362), fSCL = 1.7MHz, external clock, fSAMPLE = 94.4ksps, single-ended, unipolar, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 3.3V (MAX1361), VDD = 5V (MAX1362), fSCL = 1.7MHz, external clock, fSAMPLE = 94.4ksps, single-ended, unipolar, TA = +25°C, unless otherwise noted.) MONITOR-MODE SUPPLY CURRENT vs. SPEED GAIN ERROR vs. SUPPLY VOLTAGE 0.9 600 SUPPLY CURRENT (µA) 0.8 0.7 0.6 0.5 0.4 0.3 MAX1361 toc14 700 MAX1361 toc13 1.0 GAIN ERROR (LSB) MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response 500 INTERNAL REF 400 300 EXTERNAL REF 200 0.2 100 0.1 0 2.7 3.2 3.7 4.2 4.7 0 5.2 0 25 VDD (V) 50 75 100 125 150 SPEED (ksps) Pin Description PIN NAME FUNCTION 1 AIN0 Analog Input 2 AIN1 Analog Input 3 AIN2 Analog Input 4 AIN3/VREF 5 A0 I2C Address Select Input. Connect to VDD or GND. See Table 1. 6 INT Active-Low, Open-Drain Interrupt Output 7 SCL I2C Clock Input 8 SDA I2C Data Input/Output 9 GND Ground 10 VDD Positive Supply Voltage. Bypass VDD to GND with a 0.1µF capacitor. Analog Input or Reference Input or Output. See Table 3. Functional Diagram VDD CLK I2C INTERFACE SDA SCL A0 10-BIT ADC CONTROL INT INT REF TRIP THRESHOLDS AIN0 AIN1 4:1 MUX AIN2 AIN3/ REF MAX1361/MAX1362 GND 8 _______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response MAX1361/MAX1362 tR tF SDA tSU.DAT tHD.DAT tLOW tHD.STA tBUF tSU.STA tSU.STO 9 SCL tSU.STA tHIGH tR tF S ACK Sr P S Figure 1a. F/S-Mode 2-Wire Serial-Interface Timing tRDA tFDA SDA tSU.DAT tHD.DAT tLOW tHD.STA tSU.STA 1 9 tSU.STO SCL tHD.STA tHIGH tRCL tFCL tRCL1 Sr ACK Sr P HS-MODE S F/S-MODE Figure 1b. HS-Mode 2-Wire Serial-Interface Timing Detailed Description The MAX1361/MAX1362 4-channel ADCs use successive-approximation conversion techniques and fully differential input track/hold (T/H) circuitry to capture and convert analog signals to a serial 10-bit digital output. The MAX1361/MAX1362 feature a monitor mode with programmable trip thresholds and window comparator. The monitor function asserts an interrupt when any channel violates the programmed upper or lower thresholds. SMBus alert response allows the host microcontroller (µC) to quickly identify which device caused the interrupt. A programmable delay between monitoring intervals lowers power consumption at lower monitor rates. The MAX1361/MAX1362 integrate an internal voltage reference and clock. The software configures the analog inputs for unipolar/bipolar and single-ended/fully differential operation. Integrated first-in/first-out (FIFO) allows conversion of all channels, or eight conversions VDD IOL VOUT SDA 400pF IOH Figure 2. Load Circuits on a selected channel to reduce interface overhead. An I2C-compatible serial interface complies with standard, fast, and high-speed (1.7MHz) modes. _______________________________________________________________________________________ 9 Power Supply 10 conversion clock cycles and is equivalent to transferring a charge of 11pF x (VIN+ - VIN-) from CT/H to the binary-weighted capacitive DAC, forming a digital representation of the analog-input signal. Use a low source impedance to ensure an accurate sample. A source impedance of up to 1.5kΩ does not significantly degrade sampling accuracy. For larger source impedances, connect a 100pF capacitor from the analog input to GND or buffer the input. In internal clock mode, the T/H circuitry enters track mode on the eighth rising clock edge of the address byte (see the Slave Address section). The T/H circuitry enters hold mode on the falling clock edge of the acknowledge bit of the address byte (the ninth clock pulse). The conversions are then internally clocked, during which time the MAX1361/MAX1362 hold SCL low. In external clock mode, the T/H circuitry enters track mode after a valid address on the rising edge of the clock during the read bit (R/W = 1, bit 8). Hold mode is entered on the rising edge of the second clock pulse during the shifting out of the 1st byte of the result. The next 10 clock cycles perform the conversions (see Figure 13). The time required for the T/H circuitry to acquire an input signal is a function of the input sample capacitance. If the analog-input source impedance is high, the acquisition-time constant lengthens and more time must be allowed between conversions. The acquisition time (tACQ) is the minimum time needed for the signal to be acquired. It is calculated by: tACQ ≥ 7 x (RSOURCE + RIN) x CIN The MAX1361 (2.7V to 3.6V) and MAX1362 (4.5V to 5.5V) operate from a single supply and consume 670µA (typ) at sampling rates up to 94.4ksps and 436µA in monitor mode at 150ksps. The MAX1361 features a 2.048V internal reference and the MAX1362 features a 4.096V internal reference. All devices can be configured for use with an external reference from 1V to V DD. Bypass V DD to GND using a 0.1µF or greater ceramic capacitor for best performance. Analog Input and Track/Hold The MAX1361/MAX1362 analog-input architecture contains an analog-input multiplexer (MUX), fully differential T/H, comparator, and a fully differential switched capacitive digital-to-analog converter (DAC). Figure 3 shows the equivalent input circuit for the MAX1361/ MAX1362. In single-ended mode, the analog-input MUX connects CT/H between the analog input selected by CS[3:0] and GND (see the Configuration/Setup Bytes (Write Cycle) section). In differential mode, the analog-input MUX connects CT/H to the plus and minus analog inputs selected by CS[3:0]. During the acquisition interval, the T/H switches are in the track position, and CT/H charges to the analog-input signal. At the end of the acquisition interval, the T/H switches move to the hold position, retaining the charge on CT/H as a stable sample of the input signal. During the conversion, a switched capacitive DAC adjusts to restore the comparator input voltage to 0V within the limits of 10-bit resolution. This action requires HOLD ANALOG INPUT MUX REF CT/H AIN0 AIN1 HOLD AIN3/REF TRACK VDD/2 HOLD AIN2 CAPACITIVE DAC TRACK HOLD TRACK TRACK MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response CAPACITIVE DAC TRACK CT/H HOLD REF MAX1361 MAX1362 Figure 3. Equivalent Input Circuit 10 ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Analog-Input Bandwidth The MAX1361/MAX1362 feature input-tracking circuitry with a 5MHz small-signal bandwidth. The 5MHz input bandwidth makes it possible to digitize high-speed transient events and measure periodic signals with bandwidths exceeding the ADC’s sampling rate by using undersampling techniques. To avoid high-frequency signals from aliasing into the frequency band of interest, use anti-aliasing filtering. Analog-Input Range and Protection Internal protection diodes clamp the analog inputs to VDD and GND. These diodes allow the analog inputs to swing from (GND - 0.3V) to (VDD + 0.3V) without causing damage to the device. For accurate conversions the inputs must remain within 50mV below GND or above VDD. Single-Ended/Differential Input The SE/DIF of the configuration byte configures the MAX1361/MAX1362 analog-input circuitry for singleended or differential input. In single-ended mode (SE/DIF = 1), the digital conversion results are the difference between the analog input selected by CS[3:0] and GND. In differential mode (SE/DIF = 0), the digital conversion results are the difference between the plus and the minus analog inputs selected by CS[3:0] (see Tables 5 and 6). Unipolar/Bipolar Unipolar mode sets the differential input range from 0 to VREF. A negative differential analog input in unipolar mode causes the digital output code to be zero. Selecting bipolar mode sets the differential input range to ±VREF / 2. The digital output code is binary in unipolar mode and two’s complement in bipolar mode. (See the Transfer Functions section.) In single-ended mode the MAX1361/MAX1362 always operate in unipolar mode. The analog inputs are internally referenced to GND with a full-scale input range from 0 to VREF (Table 7). Reference SEL[1:0] of the setup byte controls the reference and the AIN3/REF configuration. When AIN3/REF is configured as a reference input or reference output (SEL0 = 1), differential conversions on AIN3/REF appear as if AIN3/REF is connected to GND. A single-ended conversion in scan mode on AIN3/REF is ignored by an internal limiter that sets the highest available channel at AIN2 (Table 2). Internal Reference The internal reference is 2.048V for the MAX1361 and 4.096V for the MAX1362. SEL0 of the setup byte controls whether AIN3/REF is used for an analog input or a reference (SEL0 = 0 selects AIN3/REF as AIN3, and SEL0 = 1 selects AIN3/REF as REF). Decouple AIN3/REF to GND with a 0.1µF capacitor and a 2kΩ resistor in series when AIN3/REF is configured as an internal reference output (SEL[1:0] = 11). See the Typical Operating Circuit. Once powered up, the reference remains on until reconfigured. Do not use the reference to supply current for external circuitry. External Reference The external reference ranges from 1V to VDD. For maximum conversion accuracy, the reference must deliver 40µA and have an impedance of 500Ω or less. For noisy or high-output-impedance references, insert a 0.1µF bypass capacitor to GND as close to AIN3/REF as possible. Clock Modes The clock mode determines the conversion clock and the data acquisition and conversion time. The clock mode also affects the scan mode. The state of the setup byte’s INT/EXT clock bit determines the clock mode. At power-up, the MAX1361/MAX1362 default to internal clock mode (INT/EXT clock = 0). Internal Clock See the Configuration/Setup Bytes (Write Cycle) section. In internal clock mode (INT/EXT clock = 0), the MAX1361/ MAX1362 use an internal oscillator for the conversion clock. The MAX1361/MAX1362 begin tracking the analog input after a valid address on the eighth rising edge of the clock. On the falling edge of the ninth clock, the analog signal is acquired and the conversion begins. While converting, the MAX1361/MAX1362 hold SCL low (clock stretching). After completing the conversion, the results are stored in internal memory. For scan-mode configurations with multiple conversions (see the Scan Modes section), all conversions happen in succession with each additional result stored in memory. Once all conversions are complete, the MAX1361/MAX1362 release SCL, allowing it to go high. The master can now clock the results out in the same order as the scan conversion. The converted results are read back in a FIFO sequence. If AIN3/REF is configured as a reference input or output, AIN3/REF is excluded from multichannel scan. If reading continues past the final result stored in memory, the pointer wraps around and points to the first result. Only the current conversion results are read from memory. The MAX1361/MAX1362 must ______________________________________________________________________________________ 11 MAX1361/MAX1362 where RSOURCE is the analog-input source impedance, RIN = 2.5kΩ, and CIN = 22pF. For internal clock mode, tACQ = 1.5 / fSCL, and for external clock mode tACQ = 2 / fSCL. MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response be addressed with a read command to obtain new conversion results. high voltage spikes on the bus lines and minimize crosstalk and undershoot of the bus signals. External Clock See the Configuration/Setup Bytes (Write Cycle) section. When configured for external clock mode (INT/EXT = 1), the MAX1361/MAX1362 use SCL as the conversion clock. In external clock mode, the MAX1361/MAX1362 begin tracking the analog input on the eighth rising clock edge of a valid slave address byte. Two SCL clock cycles later, the analog signal is acquired and the conversion begins. Unlike internal clock mode, converted data is clocked out immediately in the format described in the Reading a Conversion (Read Cycle) section. The device continuously converts input channels dictated by the scan mode until given a not acknowledge (NACK). There is no need to readdress the device with a read command to obtain new conversion results. One bit transfers during each SCL clock cycle. A minimum of nine clock cycles is required to transfer a byte in or out of the MAX1361/MAX1362 (8 bits and an ACK/NACK). The data on SDA must remain stable during the high period of the SCL clock pulse. Changes in SDA while SCL is high and stable are considered control signals (see the START and STOP Conditions section). Both SDA and SCL remain high when the bus is not busy. The conversion must complete in 1ms or droop on the T/H capacitor degrades conversion results. Use internal clock mode if the SCL clock period exceeds 60µs. Use external clock mode for conversion rates from 40ksps to 94.4ksps. Use internal clock mode for conversions under 40ksps. Internal clock mode consumes less power. Monitor mode always uses internal clock mode regardless of conversion rate. Applications Section Power-On Reset The configuration and setup registers default to a single-ended, unipolar, single-channel conversion on AIN0 using the internal clock with VDD as the reference and AIN3/REF configured as an analog input. The memory contents are unknown at power-up (see the Software Description section). I2C-Compatible 2-Wire Serial Interface The MAX1361/MAX1362 use an I2C-compatible 2-wire interface consisting of a serial data line (SDA) and serial clock line (SCL). SDA and SCL facilitate bidirectional communication between the MAX1361/MAX1362 and the master at rates up to 1.7MHz. The master (typically a microcontroller) initiates data transfer on the bus and generates the SCL signal to permit data transfer. The MAX1361/MAX1362 behave as I2C slave devices that transfer and receive data. SDA and SCL must be pulled high for proper I2C operation. This is typically done with pullup resistors (750Ω or greater). Series resistors (RS) are optional (see the Typical Operating Circuit section). The resistors protect the input architecture of the MAX1361/MAX1362 from START and STOP Conditions The master initiates a transmission with a START condition (S), which is a high-to-low transition on SDA while SCL is high. The master terminates a transmission with a STOP condition (P), which is a low-to-high transition on SDA while SCL is high (Figure 4). A repeated START condition (Sr) can be used in place of a STOP condition to leave the bus active and the mode unchanged (see the HS I2C Mode section). Acknowledge and Not-Acknowledge Conditions Data transfers are framed with an acknowledge bit (ACK) or a not-acknowledge bit (NACK). Both the master and the MAX1361/MAX1362 (slave) generate acknowledge bits. To generate an acknowledge, the receiving device must pull SDA low before the rising edge of the acknowledge-related clock pulse (ninth pulse) and keep it low during the high period of the clock pulse (Figure 5). S P Sr SDA SCL Figure 4. START and STOP Conditions S NOT ACKNOWLEDGE SDA ACKNOWLEDGE SCL 1 2 Figure 5. Acknowledge Bits 12 ______________________________________________________________________________________ 8 9 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response S 0 1 1 0 1 0 0 R/W ACK SDA 1 SCL 2 3 4 5 6 7 8 9 Figure 6. MAX1361/MAX1362 Slave Address Byte Table 1. I2C Slave Selection Table A0 STATE SUFFIX ADDRESS Low EUB 0110100 High EUB 0110101 Low MEUB 0110110 High MEUB 0110111 Low LEUB 0110010 High LEUB 0110011 base address options, allowing up to 6 devices concurrently per I2C bus (see Table 1). The MAX1361/MAX1362 continuously wait for a START condition followed by its slave address. When the device recognizes its slave address, it is ready to accept or send data depending on the R/W bit (Figure 6). HS I2C Mode At power-up, the MAX1361/MAX1362 bus timing is set for fast mode (F/S mode, up to 400kHz I2C clock), which limits the conversion rate to approximately 22ksps. Switch to high-speed mode (HS mode, up to 1.7MHz I2C clock) to achieve conversion rates up to 94.4ksps. The MAX1361/MAX1362 convert up to 150ksps in monitor mode, regardless of I2C mode. If conversion results are unread, I2C bandwidth limitations do not apply in monitor mode. Select HS mode by addressing all devices on the bus with the HS-mode master code 0000 1XXX (X = don’t care). After successfully receiving the HS-mode master code, the MAX1361/MAX1362 issue a NACK, allowing SDA to be pulled high for one clock cycle (Figure 7). To generate a not-acknowledge condition, the receiver allows SDA to be pulled high before the rising edge of the acknowledge-related clock pulse, and leaves SDA high during the high period of the clock pulse. Monitoring the acknowledge bits allows for detection of unsuccessful data transfers. An unsuccessful data transfer happens if a receiving device is busy or if a system fault has occurred. In the event of an unsuccessful data transfer, the bus master reattempts communication at a later time. Slave Address The MAX1361/MAX1362 have a 7-bit I 2 C slave address. The slave address is selected using A0. The MAX1361/MAX1362 (EUB, MEUB, and LEUB) have 3 After the NACK, the MAX1361/MAX1362 operate in HS mode. Send a repeated START (Sr) followed by a slave address to initiate HS-mode communication. If the master generates a STOP condition the MAX1361/MAX1362 HS-MODE MASTER CODE S 0 0 0 0 1 X X X NACK Sr SDA SCL F/S MODE HS MODE Figure 7. F/S-Mode to HS-Mode Transfer ______________________________________________________________________________________ 13 MAX1361/MAX1362 SLAVE ADDRESS MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response START CONDITION START R/W BIT FROM THE MASTER ADDRESS FROM THE MASTER 0 CONFIGURATION BYTE FROM THE MASTER A SETUP BYTE FROM THE MASTER A A STOP Figure 8. Example of Writing Setup and Control Bytes START CONDITION START R/W BIT FROM THE MASTER ADDRESS FROM THE MASTER CH 0 LT [11:4] A 0 A MONITOR SETUP BIT SETUP BYTE FROM THE MASTER CH 0 LT [3:0]; UT [11:8] A 1 A CH 0 UT [7:0] ALARM RESET, SCAN SPEED, INT_EN A CH 1 LT [11:4] A A STOP Figure 9. Example of Extended Setup-Byte Writing Table 2. Configuration Byte Format* BIT NAME 7(MSB) CONFIG The configuration byte always starts with 0. 6 SCAN1 5 SCAN0 SCAN1, SCAN0 = [0,0], scans from channel 0 to the upper channel chosen by CS1, CS0. SCAN1, SCAN0 = [0,1], converts a single channel chosen by CS1, CS0 eight times. SCAN1, SCAN0 = [1,0] monitor mode monitors from channel 0 to the upper channel chosen by CS1, CS0. SCAN1, SCAN0 = [1,1], single channel conversion for the channel is chosen by CS0, CS1. 4 CS3 3 CS2 2 CS1 1 CS0 0 SE/DIF DESCRIPTION CS3, CS2 = [1,1] enables readback of monitor-mode setup data. Selects the upper limit of the channel range used for the conversion sequence in scan modes SCAN = [0,0] and monitor modes SCAN = [1,0]. Selects the conversion channel when SCAN = [0,1] or when SCAN = [1,1]. (Tables 5 and 6) 1 = single-ended inputs. 0 = differential inputs. AIN0 and AIN1 form the first differential pair and AIN2 and AIN3 form the second differential pair. (See Tables 4 and 5.) Selects single-ended or differential conversions. In single-ended mode, input signal voltages are referenced to GND. In differential mode, the voltage difference between two channels is measured. When single-ended mode is used, the MAX1361/MAX1362 perform unipolar conversions regardless of the UNI/BIP bit in the setup byte. (Table 7) *Power-on defaults: 0x01 14 ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Software Description Configuration/Setup Bytes (Write Cycle) A write cycle begins with the bus master issuing a START condition followed by 7 address bits and a write bit (R/W = 0). If the address byte is successfully received, the MAX1361/MAX1362 (slave) issue an ACK. The master then writes to the slave. If the most significant bit (MSB) is 1, the slave recognizes the received byte as the setup byte (Table 4). If the MSB is 0, the slave recognizes that byte as the configuration byte (Table 2). Write to the configuration byte before writing to the setup byte (Figure 8). If enabling RESET in the setup byte, rewrite the configuration byte after writing the setup byte, since RESET clears the contents of the configuration byte back to the power-up state. When the monitor-setup bit of the setup byte is set to 1, writing extends up to 13 bytes to clock in monitor-setup data. Terminate writing monitor-setup data at any time by issuing a STOP or repeated START condition. If the slave receives a byte successfully, it issues an ACK (Figure 9). Note: When operating in HS mode, a STOP condition returns the bus into F/S mode (see the HS I2C Mode section). Automatic Shutdown AutoShutdown occurs between conversions when the MAX1361/MAX1362 are idle. When operating in external clock mode, issue a STOP, NACK, or repeated START condition to place the devices in idle mode and benefit from automatic shutdown. A STOP condition is not necessary in internal clock mode for automatic shutdown because power-down occurs once all conversions are complete. Shutdown reduces supply current to less than 0.5µA (external reference mode, typ) and 300µA (internal reference mode, typ). When idle, the MAX1361/MAX1362 continuously wait for a START condition followed by their slave address. Upon reading a valid address byte, the MAX1361/ MAX1362 power up. The internal reference requires 10ms to wake up. Therefore, power up the internal reference 10ms prior to conversion or leave the reference continuously powered. Wake-up is transparent when using an external reference or VDD as the reference. Automatic shutdown results in dramatic power savings, particularly at slow conversion rates with internal clock. For example, using an external reference at a conversion rate of 10ksps, the average supply current for the MAX1361 is 60µA (typ) and drops to 6µA (typ) at 1ksps. At 0.1ksps, the average supply current is just 1µA. Table 3 shows AIN3/REF configuration and reference power-down state. Scan Modes SCAN1 and SCAN0 of the configuration byte set the scan-mode configuration. When configuring AIN3/REF for reference input or output (SEL0 = 1), AIN3/REF is excluded from a multichannel scan. The scanned results write to memory in the same order as the conversion. Start a conversion sequence by initiating a read with the desired scan mode. Read the results from memory in the order they were converted (see the Reading a Conversion (Read Cycle) section). Selecting channel scan mode [0,0] starts converting from channel 0 up to the channel chosen by CS1, CS0. Selecting channel scan mode [0,1] converts the channel selected by CS1, CS0 eight times and returns eight consecutive results. Selecting monitor mode [1,0] initiates a continuous conversion scan sequence from channel 0 to the channel selected by CS1, CS0. See the Monitor Mode section for more details. Selecting channel scan mode [1,1] performs a single conversion on the channel selected by CS1, CS0 and returns the result. Table 3. Reference Voltage and AIN3/REF Format SEL1 SEL0 INT REF POWERDOWN AIN3/REF INTERNAL REFERENCE STATE 0 0 X 0 1 X VDD Analog input Always off External reference Reference input 1 0 0 Internal reference Always off Analog input Always off 1 0 1 1 1 0 Internal reference Analog input Always on Internal reference Reference output 1 1 1 Always off Internal reference Reference output Always on REFERENCE VOLTAGE ______________________________________________________________________________________ 15 MAX1361/MAX1362 return to F/S mode. Use a repeated START condition (Sr) in place of a STOP condition to leave the bus active and the mode unchanged. MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Table 4. Setup-Byte Format* BIT NAME 7 (MSB) Setup DESCRIPTION 6 REF/AIN SEL1 5 REF/AIN SEL0 4 INT REF Power Down 3 INT/EXT Clock Setup byte always starts with 1. When [0,0], REF/AIN3 = AIN3, REF = VDD. When [0,1], REF/AIN3 = REF, REF = external reference. When [1,0], REF/AIN3 = AIN3, REF = internal reference. When [1,1], REF/AIN3 = REF, REF = internal reference. (Table 3) 1 = internal reference always powered up. 0 = internal reference always powered down. (Table 3) 0 = internal clock. 1 = external clock (MAX1361/MAX1362 use the SCL clock for conversions). 2 UNI/BIP 0 = unipolar. 1 = bipolar. Selects unipolar or bipolar conversion mode. In unipolar mode, analog signal in 0 to VREF range can be converted. In differential bipolar mode, input signal can range from -VREF / 2 to +VREF / 2. When single-ended mode is chosen, the SE/DIF bit of configuration byte overrides UNI/BIP, and conversions are performed in unipolar mode. 1 Reset 1 = no action. 0 = resets INT and configuration register. Setup register and channel trip thresholds are unaffected. 0 Monitor Setup 0 = no action. 1 = extends writing up to 13 bytes (104 bits) of alarm reset mask. Scans speed selection and alarm thresholds. See the Configuring Monitor Mode section. *Power-on defaults: 0x82 Table 7. SE/DIF and UNI/BIP Table Table 5. Channel Selection in SingleEnded Mode (SE/DIF = 1) CS1 CS0 CH0 0 0 + 0 1 1 0 1 1 CH1 CH2 CH3 + + SE/DIF UNI/BIP 0 0 Differential inputs, unipolar 0 1 Differential inputs, bipolar 1 0 Single-ended inputs, unipolar 1 1 Single-ended inputs, unipolar MODE + Reading a Conversion (Read Cycle) Table 6. Channel Selection in Differential Mode (SE/DIF = 0) 16 CS1 CS0 CH0 CH1 0 0 + - CH2 CH3 0 1 - + 1 0 + - 1 1 - + Initiate a read cycle to start a conversion sequence and to obtain conversion results. See the Scan Modes section for details on the channel-scan sequence. Read cycles begin with the bus master issuing a START condition followed by 7 address bits and a read bit (R/W = 1). After successfully receiving the address byte, the MAX1361/MAX1362 (slave) issue an ACK. The master then reads from the slave. (See Figures 10–13.) The result is transmitted in 2 bytes. The 1st byte consists of a leading 1 followed by a 2-bit binary channel address tag, a 12/10 bit flag (0 for the MAX1361/ MAX1362), 2 bits of 1s, the first 2 bits of the data result, and the expected ACK from the master. The 2nd byte ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable HIGH CH1 CH0 10 12/1 1 0/1 0/1 0 = 10b 1 = 12b HIGH HIGH 1 1 START CONDITION DATA (MSB) D8 0/1 0/1 ACK D7 D6 D5 D4 D3 D2 D1 D0 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 ACK/ NACK R/W ADDRESS START FROM THE MASTER 1 1, CH ADD, 10b/12b FLAG, 1,1 RESULT (2 MSBs) ACK ACK tACQ ACK RESULT (8 LSBs) STOP tCONV Figure 10. Example of Reading the Conversion Result—External Clock Mode R/W ADDRESS START FROM THE MASTER 1 ACK MAX1361/MAX1362 1, CH ADD, 10b/12b, 1,1 KEEPS SCL LOW RESULT (2 MSBs) ACK RESULT (8 LSBs) ACK STOP 6.8µs MAX tACQ tCONV Figure 11. Example of a Single Conversion Using the Internal Clock, SCAN = 1,1 R/W START ADDRESS FROM THE MASTER 1 MAX1361/MAX1362 KEEPS SCL LOW ACK CONVERSION 1 tACQ CONVERSION 2 tCONV tACQ tCONV 6.8µs MAX MAX1361/MAX1362 KEEPS SCL LOW 1, CH ADD, 10b/12b, 1,1 RESULT (2 MSBs) ACK RESULT 1 (8 LSBs) ACK CONVERSION N tACQ tCONV 1, CH ADD, 10b/12b, 1,1 RESULT (2 MSBs) ACK RESULT N (8 LSBs) ACK STOP Figure 12. Example of Scan-Mode Conversions Using the Internal Clock, SCAN = 0,0 and 0,1 ______________________________________________________________________________________ 17 MAX1361/MAX1362 Table 8. Data Format MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response R/W ADDRESS START FROM THE MASTER 1 ACK 1, CH ADD, 10b/12b 1,1 RESULT (2 MSBs) ACK tACQ 1, CH ADD, 10b/12b, 1,1 RESULT (2 MSBs) tACQ ACK RESULT N (8 LSBs) CONVERSION N RESULT (8 LSBs) CONVERSION 1 ACK tACQ ACK tACQ Figure 13. Example of Scan-Mode Conversions Using the External Clock, SCAN = 0,0 and 0,1 contains D7–D0. To read the next conversion result, issue an ACK. To stop reading, issue a NACK. When the MAX1361/MAX1362 receive a NACK, they release SDA allowing the master to generate a STOP or a repeated START condition. 6) Clears the alarm register. See the Configuring Monitor Mode section. Monitor Mode Writing SCAN1 and SCAN0 bits = [1,0] in the configuration byte activates monitor mode. The MAX1361/ MAX1362 scan from channels 0 up to the channel selected by [CS1:CS0] at a rate determined by the scan delay bits. The MAX1361/MAX1362 compare the conversion results with the lower and upper thresholds for each channel. When any conversion exceeds the threshold, the MAX1361/MAX1362 assert an interrupt by pulling INT low (if enabled). The MAX1361/ MAX1362 set the corresponding flag bit in the alarmstatus register and write conversion results to the latched-fault register to record the event causing the alarm condition. INT active state is randomly delayed with respect to the conversion. Depending on the number of channels scanned and the position in the channel scan sequence, the maximum possible delay for asserting INT is five conversion periods (34µs typ, delay = 0,0,0). Monitor-Mode Overview The MAX1361/MAX1362 automatically monitor up to four input channels. For systems with limited I2C bandwidth, monitor mode allows the µC to set a window by programming lower and upper thresholds during initialization, and only intervening if the MAX1361/MAX1362 detect an alarm condition. This allows an interrupt-driven approach as an alternative to continuously polling the ADC with the µC. Monitor mode reduces processor overhead and conserves I2C bandwidth. The following shows an example of events in monitor mode: 1) Fault condition(s) detected, INT asserted. 2) Host µC services interrupt and send SMBus alert to identify the alarming device. The MAX1361/ MAX1362 respond with the I 2 C slave address, pending arbitration rules. (See the SMBus Alert section.) 3) The MAX1361/MAX1362 release the INT. 4) Host-µC reads the alarm-status register, latchedfault register, and current-conversion results to determine the alarming channel(s) and course of action. 5) Host µC services alarm(s); adjusts system parameters as needed and/or adjust lower and upper thresholds. 18 7) Monitor mode resumes. 8) If there is still an active fault, the device asserts INT again. See step 1. Configuring Monitor Mode To write monitoring setup data, set the monitor-setup bit (bit 0 in setup byte) to 1 to extend writing up to 104 bits (13 bytes) of monitoring setup data. The number of bits written to the MAX1361/MAX1362 depends on whether the part is in single-ended or differential mode and whether the upper channel limit is set by [CS1:CS0] (Table 9). Terminate writing at any time by using a STOP or repeated START condition. Previous monitoring setup data not overwritten remains valid. ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Alarm reset, scan speed, INT_EN , (8 bits) AIN1 thresholds (skip if differential mode, or CS1, CS0 < 1) (24 bits) AIN0 thresholds (24 bits) AIN2 thresholds (skip if CS1, CS0 < 2) (24 bits) AIN3 thresholds (skip if differential mode, or CS1, CS0 < 3) (24 bits) Table 10. Alarm Reset, Scan Speed Register, and INT_EN Data Format RESET RESET RESET RESET ALARM CH 0 ALARM CH 1 ALARM CH 2 ALARM CH 3 0/1 0/1 0/1 DELAY 2 DELAY 1 DELAY 0 INT_EN 0/1 0/1 0/1 0/1 0/1 Table 11. Delay Settings DELAY 2 DELAY 1 DELAY 0 A 1 written to the reset alarm CH_ clears the alarm, otherwise no action occurs (Table 10). Deassert INT by clearing all alarms or by initiating an SMBus alert during an alarm condition (see the SMBus Alert section) MONITOR-MODE CONVERSION RATE (ksps) 0 0 0 150.0* 0 0 1 75.0 0 1 0 37.5 0 1 1 18.8 1 0 0 9.4 1 0 1 4.7 1 1 0 2.3 1 1 1 1.2 The Delay 2, Delay 1, Delay 0 bits set the speed of monitoring by changing the delay between conversions. Delay 2, 1, 0 = 000 sets the maximum possible speed; 001 divides the maximum speed by ~2. Increasing delay values further divides the previous speed by two (Table 11). INT_EN controls the open-drain INT output. Set INT_EN to 1 to enable the hardware interrupt. Set INT_EN to 0 to disable the hardware interrupt output. The INT output is high impedance when disabled or when there are no alarms. The master can also poll the alarm status register at any time to check the alarm status. *When using delay = [0,0,0] in internal reference mode and AIN3/REF configured as a REF output, the MAX1361/MAX1362 may exhibit a code-dependant gain error due to insufficient internal reference drive. Gain error caused by this phenomenon is typically less than 1%FSR (0.1µF CREF in series with a 2kΩ resistor) and increases with a larger CREF. Avoid this gain error by using an external reference, VDD, as a reference or use an internal reference with AIN3/REF as an analog input (see Table 4). Alternatively, choose delay bits other than [0,0,0] to lower the conversion rate. Repeat clocking channel threshold data up to the channel programmed by CS1 and CS0 (Table 12). For differential input mode, omit odd channels; the lower and upper threshold data applies to channel pairs. There is no need to clock in dummy data for odd (or even) channels (Table 6). Table 12. Lower and Upper Threshold Data Format BYTE B7 B6 B5 B4 B3 B2 B1 B0 ACKNOWLEDGE 1 X X LT9 (MSB) LT8 LT7 LT6 LT5 LT4 ACK 2 LT3 LT2 LT1 LT0 (LSB) X X UT9 (MSB) UT8 ACK 3 UT7 UT6 UT5 UT4 UT3 UT2 UT1 UT0 (LSB) ACK X = Don’t care. ACK = Acknowledge. ______________________________________________________________________________________ 19 MAX1361/MAX1362 Table 9. Monitor-Mode Setup Data Format MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Table 13. Readback-Mode Format AIN1 THRESHOLDS AIN0 AIN2 THRESHOLDS (SKIP IF DIFFERENTIAL THRESHOLDS (SKIP IF CS1, CS0 < 2) MODE OR CS1, CS0 < 1) SCAN SPEED AND INT_EN 1 1 1 1 D2 D1 D0 INT_EN 24 bits 24 bits AIN3 THRESHOLDS (SKIP IF DIFFERENTIAL MODE OR CS1, CS0 < 3) 24 bits 24 bits Table 14. Reading in Monitor-Mode Data Format ALARM-STATUS REGISTER LATCHED-FAULT REGISTER CURRENT-CONVERSION RESULTS 8 bits 16, 32, 48, or 64 bits (depends on CSO, CS1, and SE/DIF) 16, 32, 48, or 64 bits (depends on CSO, CS1, and SE/DIF) Table 15. Alarm-Status Register CH0 UP CH0 LOW CH1 UP CH1 LOW CH2 UP CH2 LOW CH3 UP CH3 LOW 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 = Not-alarm condition. 1 = Alarm condition. Table 16. Latched-Fault and CurrentConversion Register AIN0 AIN1 AIN2 AIN3 16-bit read 16-bit read 16-bit read 16-bit read To disable alarming on a specific channel, set the lower threshold to 0x800 and the upper threshold to 0x7FF for bipolar mode, or set the lower threshold to 0x000 and the upper threshold to 0xFFF for unipolar mode. Readback Mode Select readback mode by setting CS3, CS2 to [1,1] in the configuration byte. Begin a read operation to start reading back monitor-setup data. Clock out delay bit settings, INT_EN bit, and the lower and upper thresholds programmed for each channel. Readback mode follows exactly the same format as writing to the monitor-setup data, with the exception of the first 4 alarmreset bits, which are always 1 (Table 13). Reading in Monitor Mode Reading in monitor mode reads back the alarm-status register, latched-fault register, and current-conversion results as shown in Table 14. The MAX1361/MAX1362 register pointer loops back to the beginning of the current-conversion result after reading the last conversion result. Stop reading at any time by asserting a STOP condition or NACK. Note: The MAX1361/MAX1362 do not update the currentconversion results register while reading in monitor mode. 20 Monitor mode resumes after a STOP condition or NACK. Alarm-Status Register The latched-fault register records a snapshot of the alarming channel at the instance that a fault condition is asserted. An alarm-status bit of 1 (Table 15) indicates a fault, and the data in the latched-fault register of the corresponding channel contains the conversion result that caused the alarm to trip. Resetting alarms does not clear the latched-fault register, thus the latched-fault register contains valid data only if an alarm status bit is high for the given channel. The current-conversion register contains the most recent conversion results. If the user attempts to read past the last result of the current-conversion register, the MAX1361/MAX1362 wraps back to the beginning of the current-conversion result. The latched-fault register and current-conversion register follow the data format detailed in Tables 8 and 16. Register length depends on the number of conversions in one monitoring sequence. For example, when channel pairs 0/1 and channels 2/3 are monitored differentially, there are only two conversion results to report. The latched-fault register is 2 x 16 bits long, after which two current-conversion results follow. Likewise, if CS0 and CS1 limit the upper bound of the channel scan range from CH0 to CH2 in single-ended mode, the latchedfault register clocks out 3 x 16 bits of data followed by the current-conversion results, also 3 x 16 bits. ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response sive-integer LSB values. Figures 14 and 15 show the transfer functions for unipolar and bipolar operations, respectively. SMBus Alert Layout, Grounding, and Bypassing The SMBus-alert feature provides a quick method to identify alarming devices on a shared interrupt. Upon receiving an interrupt signal, the host µC can broadcast a receive byte request to the alert-response slave address (0001100). Any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus. The alert response can activate several different slave devices simultaneously. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address wins as a consequence of the open-collector bus. The losing device does not generate an acknowledgement and continues to hold the alert line low until serviced. Successful reading of the alert response address deasserts INT. Only use PC boards. Wire-wrap configurations are not recommended since the layout should ensure proper separation of analog and digital traces. Do not run analog and digital lines parallel to each other, and do not layout digital signal paths underneath the ADC package. Use separate analog and digital PC board ground sections with only one star point (Figure 16). The MAX1361/MAX1362 resume monitoring after cleaning an alarm-status register. INT may immediately reassert if a fault is still present, or if the alarm register has not been thoroughly cleared. Transfer Functions Output data coding for the MAX1361/MAX1362 is binary in unipolar mode and two’s complement in bipolar mode with 1 LSB = VREF / 2N, where N is the number of bits. Code transitions occur halfway between succes- OUTPUT CODE 111...111 111...110 Definitions Integral Nonlinearity Integral nonlinearity (INL) 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 between the endpoints of the transfer function, once offset and gain errors have been nullified. The OUTPUT CODE FULL-SCALE TRANSITION 011...111 FS = REF + GND ZS = GND 011...110 000...010 100...010 100...001 High-frequency noise in the power supply (VDD) could influence the proper operation of the ADC’s fast comparator. Bypass VDD to the star ground with a network of two parallel capacitors, 0.1µF and 4.7µF, located as close as possible to the MAX1361/MAX1362 power supply. Minimize capacitor lead length for best supply noise rejection. For extremely noisy supplies, add an attenuation resistor (5Ω) in series with the power supply. 1 LSB = 100...000 000...001 VREF 1024 000...000 V FS = REF + AIN2 ZS = AIN-VREF + AIN2 V 1 LSB = REF 1024 -FS = 111...111 011...111 111...110 011...110 111...101 011...101 100...001 000...001 100...000 000...000 0 (GND) 1 -FS + 0.5 LSB 512 INPUT VOLTAGE (LSB) Figure 14. Unipolar Transfer Function FS - 0.5 LSB V AIN- ≥ REF 2 AININPUT VOLTAGE (LSB) +FS - 1 LSB Figure 15. Bipolar Transfer Function ______________________________________________________________________________________ 21 MAX1361/MAX1362 Resetting Alarm Reset alarms by writing to monitor-setup data. See the Configuring Monitor Mode section and Table 10. MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response minimum analog-to-digital noise is caused by quantization error only and results directly from the ADC’s resolution (N bits): SNR (MAX)[dB] = 6.02dB x N + 1.76dB SUPPLIES 3V OR 5V VLOGIC = 3V / 5V GND 4.7µF R* = 5Ω Signal-to-Noise Plus Distortion 0.1µF VDD In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. SNR is computed by taking the ratio of the RMS signal to the RMS noise, which includes all spectral components minus the fundamental, the first five harmonics, and the DC offset. GND 3V/5V DGND DIGITAL CIRCUITRY MAX1361 MAX1362 Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency’s RMS amplitude to RMS equivalent of all other ADC output signals. SINAD(dB) = 20 x log (SignalRMS / NoiseRMS) Effective Number of Bits *OPTIONAL Figure 16. Power-Supply Grounding Connection MAX1361/MAX1362’s INL is measured using the endpoint method. Differential Nonlinearity Differential nonlinearity (DNL) is the difference between an actual step width and the ideal value of 1 LSB. A DNL error specification of less than 1 LSB guarantees no missing codes and a monotonic transfer function. Aperture Jitter Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples. Aperture Delay Aperture delay (tAD) is the time between the falling edge of the sampling clock and the instant when an actual sample is taken. Signal-to-Noise Ratio For a waveform perfectly reconstructed from digital samples, the theoretical maximum SNR is the ratio of the full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical 22 Effective number of bits (ENOB) indicates the global accuracy of an ADC at a specific input frequency and sampling rate. An ideal ADC’s error consists of quantization noise only. With an input range equal to the ADC’s full-scale range, calculate the ENOB as follows: ENOB = (SINAD - 1.76) / 6.02 SignalRMS SINAD(dB) = 20 × log NoiseRMS + THDRMS Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the RMS sum of the input signal’s first five harmonics to the fundamental itself. This is expressed as: 2 2 2 2 V + V3 + V4 + V5 THD = 20 × log 2 V1 where V1 is the fundamental amplitude, and V2 through V5 are the amplitudes of the 2nd- through 5th-order harmonics. ______________________________________________________________________________________ 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response Typical Operating Circuit TOP VIEW 3V/5V 0.1µF AIN0 1 10 VDD AIN1 9 GND 8 SDA AIN2 AIN3/VREF A0 2 3 MAX1361 MAX1362 4 7 5 6 4.7µF VDD AIN0 AIN1 SCL ANALOG INPUTS INT 2kΩ CREF *RS MAX1361 MAX1362 SDA SCL *RS AIN3/REF µMAX INT GND 0.1µF RP 3V/5V RP 3V/5V RP µC SDA SCL INT *OPTIONAL Ordering Information/Selector Guide (continued) PART I2C SLAVE ADDRESS SUPPLY VOLTAGE (V) 10 µMAX 0110100/0110101 4.5 to 5.5 -40°C to +85°C 10 µMAX 0110010/0110011 4.5 to 5.5 -40°C to +85°C 10 µMAX 0110110/0110111 4.5 to 5.5 TEMP RANGE PIN-PACKAGE MAX1362EUB -40°C to +85°C MAX1362LEUB* MAX1362MEUB *Future product—contact factory for availability. ______________________________________________________________________________________ 23 MAX1361/MAX1362 Pin Configuration Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) e 10LUMAX.EPS MAX1361/MAX1362 4-Channel, 10-Bit, System Monitor with Programmable Trip Window and SMBus Alert Response 4X S 10 10 INCHES H Ø0.50±0.1 0.6±0.1 1 1 0.6±0.1 BOTTOM VIEW TOP VIEW D2 MILLIMETERS MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 0.120 D1 0.116 0.118 D2 0.114 E1 0.116 0.120 0.118 E2 0.114 0.199 H 0.187 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S α 0° 6° MAX MIN 1.10 0.05 0.15 0.75 0.95 2.95 3.05 2.89 3.00 2.95 3.05 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0° 6° E2 GAGE PLANE A2 c A b A1 α E1 L D1 L1 FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 10L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0061 REV. I 1 1 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 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.