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| Agilent HCPL-0872 Digital Interface IC Data Sheet Features * Interface between HCPL-7860/ 786J/7560 and MCU/DSP Description The Digital Interface IC, HCPL0872 converts the single-bit data stream from the Isolated Modulator (such as HCPL7860/786J/7560) into fifteenbit output words and provides a serial output interface that is compatible with SPI(R), QSPI(R), and Microwire(R) protocols, allowing direct connection to a microcontroller. The Digital Interface IC, HCPL-0872 is available a 300-mil wide SO-16 surface-mount package. Features of the Digital Interface IC include five different conversion modes, three different pre-trigger modes, offset calibration, fast over-range detection, and adjustable threshold detection. Programmable features are configured via the Serial Configuration port. A second multiplexed input is available to allow measurements with a second isolated modulator without additional hardware. * 5 Conversion Modes for Resolution/Speed Trade-Off * 3 Pre-Trigger Modes * Offset Calibration * Fast 3 s Over-Range Detection * Adjustable Threshold Detection * Serial I/O (SPI(R), QSPI(R) and Microwire Compatible) * Offset Calibration * -40C to +85C Operating Temperature Range Applications * Motor Phase and Rail Current Sensing * Data Acquisition Systems VDD1 Input Current VDD2 MCLK MDAT GND2 1 2 3 4 5 6 7 8 CCLK VDD 16 15 14 13 12 11 10 9 * Industrial Process Control * Inverter Current Sensing MCU or DSP VIN+ VINGND1 CONFIG CLAT INTERCHAN FACE CON VERSION CDAT SCLK INTERFACE MCLK1 MDAT1 MCLK2 SDAT * General Purpose Current Sensing and Monitoring CH1 HCPL-7860 HCPL-786J HCPL-7560 VDD1 Input Current CS THR1 VDD2 MCLK MDAT GND2 VIN+ VINGND1 THRES MDAT2 CH2 HOLD OVR1 DETECT & RESET GND RESET A 0.1 F bypass capacitor must be connected between pins VDD and Ground SPI and QSPI are trademarks of Motorola Corp. w w w .d Microwire is a trademark of National Semiconductor Inc. ee sh ta a CAUTION: It is advised that normal static precautions be taken in handling and assembly of this component to prevent damage and/or degradation, which may be induced by ESD. u. t4 om c HCPL-0872 www..com HCPL-0872 Digital Interface IC Because the two inputs are multiplexed, only one conversion at a time can be made and not all features are available for the second channel. The available features for both channels are shown in the table below CCLK 1 CLAT 2 CDAT 3 MCLK1 4 CONFIG. INTERFACE CONVERSION INTERFACE 16 VDD 15 CHAN 14 SCLK 13 SDAT 12 CS THRESHOLD DETECT & RESET 11 THR1 10 OVR1 9 RESET Feature Conversion Mode Offset Calibration Pre-Trigger Mode Over-Range Detection Adjustable Threshold Detection Channel 1 * * * * * Channel 2 * * MDAT1 5 MCLK2 6 MDAT2 7 GND 8 CH1 CH2 Pin Description, Digital Interface IC Symbol CCLK CLAT CDAT MCLK1 MDAT1 MCLK2 MDAT2 GND VDD CHAN SCLK SDAT Description Clock input for the Serial Configuration Interface (SCI). Serial Configuration data is clocked in on the rising edge of CCLK. Latch input for the Serial Configuration Interface (SCI). The last 8 data bits clocked in on CDAT by CCLK are latched into the appropriate configuration register on the rising edge of CLAT. Data input for the Serial Configuration Interface (SCI). Serial configuration data is clocked in MSB first. Channel 1 Isolated Modulator clock input. Input Data on MDAT1 is clocked in on the rising edge of MCLK1. Channel 1 Isolated Modulator data input. Channel 2 Isolated Modulator clock input. Input Data on MDAT2 is clocked in on the rising edge of MCLK2. Channel 2 Isolated Modulator data input. Digital ground. Supply voltage (4.5 V to 5.5 V). Channel select input. The input level on CHAN determines which channel of data is used during the next conversion cycle. An input low selects channel 1, a high selects channel 2. Serial clock input. Serial data is clocked out of SDAT on the falling edge of SCLK. Serial data output. SDAT changes from high impedance to a logic low output at the start of a conversion cycle. SDAT then goes high to indicate that data is ready to be clocked out. SDAT returns to a highimpedance state after all data has been clocked out and CS has been brought high. SDAT goes high immediately after RESET is released. Conversion start input. Conversion begins on the falling edge of CS. CS should remain low during the entire conversion cycle and then be brought high to conclude the cycle. Continuous, programmable-threshold detection for channel 1 input data. A high level output on THR1 indicates that the magnitude of the channel 1 input signal is beyond a user programmable threshold level between 160 mV and 310 mV. This signal continuously monitors channel 1 independent of the channel select (CHAN) signal. High speed continuous over-range detection for channel 1 input data. A high level output on OVR1 indicates that the magnitude of the channel 1 input is beyond full-scale. This signal continuously monitors channel 1 independent of the CHAN signal. Master reset input. A logic high input for at least 100 ns asynchronously resets all configuration registers to their default values and zeroes the Offset Calibration registers. CS THR1 OVR1 RESET 2 Ordering Information Specify part number followed by option number (if desired). Example: HCPL-0872-XXXX No option = Standard 16-Pin SO package, 47 units per tube. 500 = Tape and Reel Packaging Option, 1000 units per reel. XXXE = Lead-Free Option Option data sheets available. Contact Agilent sales representative or authorized distributor. Package Outline Drawings Standard 16-pin SO Package TOP VIEW PIN NO. 1 IDENTIFIER 1.27 (0.050) x 0.075 (0.003) DEPTH SHINY SURFACE 16 15 14 13 12 11 10 9 1.90 (0.075) BOTTOM VIEW 1.90 (0.075) 1.27 (0.050) x 0.075 (0.003) DEPTH (2x) EJECTOR PIN SHINY SURFACE 0.33 x 45 (0.013 x 45) 7.544 0.05 (0.297 0.002) A 0872 YYWW 10.00-10.65 (0.394-0.419) (TIP TO TIP) TH XX 1.27 (0.050) 1 2 3 4 5 6 7 8 1.27 (0.050) SIDE VIEW 1.016 0.025 (0.040 0.001) 7 2.286 (0.090) 1.27 BSC (0.050 BSC) 0.33-0.51 (0.013-0.020) R 0.18 (R 0.007) ALL CORNERS AND EDGES 0.10-0.30 (0.004-0.0118) PARTING LINE 0.01 (0.004) SEATING PLANE 10.21 0.10 (0.402 0.002) 2.386-2.586 (0.094-0.1018) A 0.23-0.32 (0.0091-0.0125) 1.016 REF. (0.040) END VIEW DIMENSIONS IN MILLIMETERS (INCHES). TOLERANCES (UNLESS OTHERWISE SPECIFIED): xx.xx = 0.010 xx.xxx = 0.002 0 - 8 0.40 - 1.27 (0.016 - 0.050) DETAIL A 3 Solder Reflow Temperature Profile 300 PREHEATING RATE 3C + 1C/-0.5C/SEC. REFLOW HEATING RATE 2.5C 0.5C/SEC. PEAK TEMP. 245C PEAK TEMP. 240C PEAK TEMP. 230C 200 2.5C 0.5C/SEC. 160C 150C 140C 3C + 1C/-0.5C 30 SEC. 30 SEC. TEMPERATURE (C) SOLDERING TIME 200C 100 PREHEATING TIME 150C, 90 + 30 SEC. 50 SEC. TIGHT TYPICAL LOOSE 0 0 50 100 TIME (SECONDS) 150 200 250 ROOM TEMPERATURE Recommended Pb-Free IR Profile tp Tp TEMPERATURE (C) TIME WITHIN 5C of ACTUAL PEAK TEMPERATURE 20-40 SEC. 260 +0/-5C 217C RAMP-UP 3C/SEC. MAX. 150 - 200 C RAMP-DOWN 6C/SEC. MAX. TL T smax T smin ts PREHEAT 60 to 180 SEC. 25 t 25C to PEAK tL 60 to 150 SEC. TIME (SECONDS) NOTES: THE TIME FROM 25 C to PEAK TEMPERATURE = 8 MINUTES MAX. Tsmax = 200C, Tsmin = 150C 4 Absolute Maximum Ratings Parameter Storage Temperature Operating Temperature Supply Voltage Input Voltage Output Voltage Lead Solder Temperature Solder Reflow Temperature Profile Recommended Operating Conditions Parameter Ambient Operating Temperature Supply Voltage Input Voltage Electrical Specifications (DC) Symbol Min. Max. -55 125 TS -40 85 TA 0 5.5 VDD All Inputs -0.5 VDD + 0.5 All Outputs -0.5 VDD + 0.5 260C for 10 sec., 1.6 mm below seating See Reflow Thermal Profile Units C C V V V plane Note 1 Notes 1. Agilent Technologies recommends the use of non-chlorinated solder fluxes. Symbol TA VDD All Inputs Min. -40 4.5 0 Max. 85 5.5 VDD Units C V V Unless otherwise noted, all Typical specifications are at TA = 25C and VDD = 5 V, and all Minimum and Maximum specifications apply over the following ranges: TA = -40C to +85C and VDD = 4.5 to 5.5 V. Parameter Supply Current DC Input Current Input Logic Low Voltage Input Logic High Voltage Output Logic Low Voltage Output Logic High Voltage Clock Frequency (CCLK, MCLK and SCLK) Clock Period (CCLK, MCLK and SCLK) Clock High Level Pulse Width (CCLK, MCLK and SCLK) Clock Low Level Pulse Width (CCLK, MCLK and SCLK) Setup Time from DAT to Rising Edge of CLK (CDAT, CCLK, MDAT and MCLK) DAT Hold Time after Rising Edge of CLK (CDAT, CCLK, MDAT and MCLK) Setup Time from Falling Edge of CLAT to First Rising Edge of CCLK Setup Time from Last Rising Edge of CCLK to Rising Edge of CLAT Delay Time from Falling Edge of SCLK to SDAT Setup Time from Data Ready to First Falling Edge of SCLK Setup Time from CHAN to falling edge of CS Reset High Level Pulse Width Symbol IDD IIN VIL VIH VOL VOH fCLK tPER tPWH tPWL tSUCLK tHDCLK tSUCL1 tSUCL2 tDSDAT tSUS tSUCHS tPWR Min. Typ. 3 0.001 Max. 5 10 0.8 0.4 20 3.6 4.3 0.15 5.0 Units mA A V V V V MHz ns ns ns ns ns ns ns Test Conditions Fig. fCLK = 10 MHz IOUT = 4 mA IOUT = -400 A 50 20 20 10 10 20 20 15 200 20 100 2, 3 2, 3 2, 3 2 2 2 2 3 3 ns ns ns ns Notes: 1. Agilent recommends the use of non-chlorinated solder fluxes. 5 Applications Information Digital Current Sensing As shown in Figure 1, using the Isolated 2-chip A/D converter to sense current can be as simple as connecting a current-sensing resistor, or shunt, to the input and reading output data through the 3-wire serial output interface. By choosing the appropriate shunt resistance, any range of current can be monitored, from less than 1 A to more than 100 A. Even better performance can be achieved by fully utilizing the more advanced features of the Isolated A/D converter, such as the pre-trigger circuit, which can reduce conversion time to less than 1s, the fast over-range detector for quickly detecting short circuits, different conversion modes giving various resolution/speed trade-offs, offset calibration mode to eliminate initial offset from measurements, and an adjustable threshold detector for detecting non-short circuit overload conditions. Product Description The Digital Interface IC, HCPL0872 converts the single-bit data stream from the Isolated Modulator (such as HCPL7860/786J/7560) into fifteenbit output words and provides a serial output interface that is compatible with SPI(R), QSPI(R), and Microwire(R) protocols, allowing direct connection to a microcontroller. A second multiplexed input is available to allow measurements with a second isolated modulator without additional hardware. The Digital Interface IC, HCPL0872 can used together with Isolated Modulator, HCPL7860/786J/7560 to form an isolated programmable twochip analog-to-digital converter. The primary functions of the HCPL-0872 Digital Interface IC are to derive a multi-bit output signal by averaging the singlebit modulator data, as well as to provide a direct microcontroller interface. The effective resolution of the multi-bit output signal is a function of the length of time NON-ISOLATED +5V (measured in modulator clock cycles) over which the average is taken; averaging over longer periods of time results in higher resolution. The Digital Interface IC can be configured for five conversion modes, which have different combinations of speed and resolution to achieve the desired level of performance. Other functions of the HCPL0872 Digital Interface IC include a Phase Locked Loop based pre-trigger circuit that can either give more precise control of the effective sampling time or reduce conversion time to less than 1s, a fast over-range detection circuit that rapidly indicates when the magnitude of the input signal is beyond fullscale, an adjustable threshold detection circuit that indicates when the magnitude of the input signal is above a user adjustable threshold level, an offset calibration circuit, and a second multiplexed input that allows a second Isolated Modulator to be used with a single Digital Interface IC. ISOLATED +5V INPUT CURRENT R SHUNT 0.02 + C1 0.1 F V DD1 V IN+ V INGND1 V DD2 MCLK MDAT GND2 C2 0.1 F CCLK CLAT CDAT MCLK1 MDAT1 MCLK2 MDAT2 GND V DD CHAN SCLK SDAT CS THR1 OVR1 RESET + C3 10 F 3-WIRE SERIAL INTERFACE HCPL-7860 HCPL-786J HCPL-7560 HCPL-0872 Figure 1. Typical Application Circuit. 6 Digital Interface Timing Power Up/Reset At power up, the digital interface IC should be reset either manually, by bringing the RESET pin (pin 9) high for at least 100 ns, or automatically by connecting a 10F capacitor between the RESET pin and VDD (pin 16). The RESET pin operates asynchronously and places the IC in its default configuration, as specified in the Digital Interface Configuration section. Conversion Timing Figure 2 illustrates the timing for one complete conversion cycle. A conversion cycle is initiated on the falling edge of the convert start signal (CS); CS should be held low during the entire conversion cycle. When CS is brought low, the serial output data line (SDAT) changes from a highimpedance to the low state, indicating that the converter is busy. A rising edge on SDAT indicates that data is ready to be clocked out. The output data is clocked out on the negative edges of the serial clock pulses (SCLK), MSB first. A total of 16 pulses is needed to clock out all of the data. After the last clock pulse, CS should be brought high again, causing SDAT to return to a high-impedance state, completing the conversion cycle. If the external circuit uses the positive edges of SCLK to clock in the data, then a total of sixteen bits is clocked in, the first bit is always high (indicating that data is ready) followed by 15 data bits. If fewer than 16 cycles of SCLK are input before CS is brought high, the conversion cycle will terminate and SDAT will go to the highimpedance state after a few cycles of the Isolated Modulator's clock. The amount of time between the falling edge of CS and the rising edge of SDAT depends on which conversion and pretrigger modes are selected; it can be as low as 0.7s when using pre-trigger mode 2, as explained in the Digital Interface Configuration section. CHAN tSUCHS CS SDAT B14 B13 B12 B11 B10 B1 B0 tDSDAT tPWH 3 4 5 tPER 6 15 16 SCLK 1 2 tC tSUS tPWL Figure 2. Conversion Timing. 7 Serial Configuration Timing The HCPL-0872 Digital Interface IC is programmed using the Serial Configuration Interface (SCI), which consists of the clock (CCLK), data (CDAT), and enable/latch (CLAT) signals. Figure 3 illustrates the timing for the serial configuration interface. To send a byte of configuration data to the HCPL-0872, first bring CLAT low. Then clock in the eight bits of the configuration byte (MSB first) using CDAT and the rising edge of CCLK. After the last bit has been clocked t SUCL1 CLAT Channel Select Timing in, bringing CLAT high again will latch the data into the appropriate configuration register inside the interface IC. If more than eight bits are clocked in before CLAT is brought high, only the last eight bits will be used. Refer to the Digital Interface Configuration section to determine appropriate configuration data. If the default configuration of the digital interface IC is acceptable, then CCLK, CDIN and CLAT may be connected to either VDD or GND. t SUCL2 The channel select signal (CHAN) determines which input channel will be used for the next conversion cycle. A logic low level selects channel one, a high level selects channel 2. CHAN should not be changed during a conversion cycle. The state of the CHAN signal has no effect on the behavior of either the over-range detection circuit (OVR1) or the adjustable threshold detection circuit (THR1). Both OVR1 and THR1 continuously monitor channel 1 independent of the CHAN signal. CHAN also does not affect the behavior of the pretrigger circuit, which is tied to the conversion timing of channel 1, as explained in the Digital Interface Configuration section. CDAT t SUCLK B7 B6 t HDCLK B5 B4 B3 B2 B1 B0 t PWH CCLK t PWL Figure 3. Serial Configuration Interface Timing. t PER 8 Digital Interface Configuration Configuration Registers The Digital Interface IC contains four 6-bit configuration registers that control its behavior. The two LSBs of any byte clocked into the serial configuration port (CDAT, CCLK, CLAT) are used as address bits to determine which register the data will be loaded into. Registers 0 and 1 (with address bits 00 and 01) specify the conversion and offset calibration modes of channels 1 and 2, register 2 (address bits 10) specifies the Table 1. Register Configuration. Register 0 Bit 7 Configuration Data Bits Bit 6 Bit 5 Bit 4 Channel 1 Conversion Mode High Low Channel 2 Conversion Mode Low Low Low Bit 3 Channel 1 Offset Cal Low Low Channel 2 Offset Cal Low Low Threshold Level Low Low Reserved Low Low Bit 2 Reserved Low Reserved Low Low Low Address Bits Bit 1 Bit 0 Conversion Mode behavior of the adjustable threshold circuit, and register 3 (address bits 11) specifies which pre-trigger mode to use for channel 1. These registers are illustrated in Table 1 below, with default values indicated in bold italic type. Note that there are several reserved bits, which should always be set low and that the configuration registers should not be changed during a conversion cycle. The conversion mode determines the speed/ resolution trade-off for the Isolated A/D converter. The four MSBs of registers 0 and 1 determine the conversion mode for the appropriate channel. The bit settings for choosing a particular conversion mode are shown in Table 2 below. Combinations of data bits not specified in Table 2 below are not recommended. High 1 Low Low 2 3 High High Threshold Detection Time High Low Pre-Trigger Mode Low Low Low High High High Low High Notes: Bold italic type indicates Default values. Reserved bits should be set low. Table 2. Conversion Mode Configuration. Conversion Mode 1 2 3 4 5 Configuration Data Bits Bit 7 Low Low High High High Bit 6 High Low High High Low Bit 5 Low High High Low High Bit 4 High High Low Low Low Notes: Bold italic type indicates Default values. 9 Pre-Trigger Mode The pre-trigger mode refers to the operation of a PLL-based circuit that affects the sampling behavior and conversion time of the A/D converter when channel 1 is selected. The PLL pre-trigger circuit has two modes of operation; the first mode allows more precise control of the time at which the analog input voltage is effectively sampled, while the second mode essentially eliminates the time between when the external convert start command is given and when output data is available (reducing it to less than 1s). A brief description of how the A/D converter works with the pre-trigger circuit disabled will help explain how the pretrigger circuit affects operation when it is enabled. With the pre-trigger circuit is disabled (pre-trigger mode 0), Figure 4 illustrates the relationship between the convert start command, the weighting function used to average the modulator data, and the data ready signal. The weighted averaging of the modulator data begins immediately following the convert start command. The weighting function increases for half of the conversion cycle and then decreases back to zero, at which time the data ready signal is given, completing the conversion cycle. The analog signal is effectively sampled at the peak of the weighting function, halfway through the conversion cycle. This is the default mode. If the convert start signal is periodic (i.e., at a fixed frequency) and the PLL pretrigger circuit is enabled (pretrigger modes 1 or 2), either the peak of the weighting function or the end of the conversion cycle can be aligned to the external convert start command, as shown in Figure 4. The Digital Interface IC can therefore synchronize the conversion cycle so that either the beginning, the middle, or the end of the conversion is aligned with the external convert start command, depending on whether pre-trigger mode 0, 1, or 2 is selected, respectively. The only requirement is that the convert start signal for channel 1 be periodic. If the signal is not periodic and pretrigger mode 1 or 2 is selected, then the pre-trigger circuit will not function properly. An important distinction should be made concerning the difference between conversion time and signal delay. As can be seen in Figure 4, the amount of time from the peak of the weighting function (when the input signal is being sampled) to when output data is ready is the same for all three modes. This is the actual delay of the analog signal through the A/D converter and is independent of the "conversion time," which is simply the time between the convert start signal and the data ready signal. Because signal delay is the true measure of how much phase shift the A/ D converter adds to the signal, it should be used when making calculations of phase margin and loop stability in feedback systems. There are different reasons for using each of the pre-trigger modes. If the signal is not periodic, then the pre-trigger circuit should be disabled by selecting pre-trigger mode 0. If the most time-accurate sampling of the input signal is desired, then mode 1 should be selected. If the shortest possible conversion time is desired, then mode 2 should be selected. The pre-trigger circuit functions only with channel 1; the circuit ignores any convert start signals while channel 2 is selected with the CHAN input. This allows conversions on channel 2 to be performed between conversions on channel 1 without affecting the operation of the pre-trigger circuit. As long as the convert start signals are periodic while channel 1 is selected, then the pre-trigger circuit will function properly. The three different pre-trigger modes are selected using bits 6 and 7 of register 3, as shown in Table 3 below. WEIGHTING FUNCTION CONVERT START - CS DATA READY - SDAT A) PRE-TRIGGER MODE 0 B) PRE-TRIGGER MODE 1 C) PRE-TRIGGER MODE 2 Figure 4. Pre-Trigger Modes 0, 1, and 2. 10 Table 3. Pre-Trigger Mode Configuration. Configuration Data Bits Pre-Trigger Mode 0 1 2 Bit 7 Low Low High Bit 6 Low High Don't Care Table 4. Offset Calibration Configuration. Configuration Data Bits Offset Calibration Mode Off On Notes: Bold italic type indicates Default values. Bit 3 Low High Notes: Bold italic type indicates Default values. Offset Calibration The offset calibration circuit can be used to separately calibrate the offsets of both channels 1 and 2. The offset calibration circuit contains a separate offset register for each channel. After an offset calibration sequence, the offset registers will contain a value equal to the measured offset, which will then be subtracted from all subsequent conversions. A hardware reset (bringing the RESET pin high for at least 100 ns) is required to reset the offset calibration registers to zero. The following sequence is recommended for performing an offset calibration: 1. Select the appropriate channel using the CHAN pin (low = channel 1, high = channel 2). 2. Force zero volts at the input of the selected isolated modulator. 3. Send a configuration data byte to the appropriate register for the selected channel (register 0 for channel 1, register 1 for channel 2). Bit 3 of the configuration byte should be set high to enable offset calibration mode and bits 4 through 7 should be set to select conversion mode 1 to achieve the highest resolution measurement of the offset. 4. Perform one complete conversion cycle by bringing CS low until SDAT goes high, indicating completion of the conversion cycle. Because bit 3 of the configuration has been set high, the uncalibrated output data from the conversion will be stored in the appropriate offset calibration register and will be subtracted from all subsequent conversions on that channel. If multiple conversion cycles are performed while the offset calibration mode is enabled, the uncalibrated data from the last conversion cycle will be stored in the offset calibration register. 5. Send another configuration byte to the appropriate register for the selected channel, setting bit 3 low to disable calibration mode and setting bits 4 through 7 to select the desired conversion mode for subsequent conversions on that channel. To calibrate both channels, perform the above sequence for each channel. The offset calibration sequence can be performed as often as needed. Table 4 below summarizes how to turn the offset calibration mode on or off using bit 3 of configuration registers 0 and 1. Over-Range Detection The over-range detection circuit allows fast detection of when the magnitude of the input signal on channel 1 is near or beyond full-scale, causing the OVR1 output to go high. This circuit can be very useful in current-sensing applications for quickly detecting when a short-circuit occurs. The over-range detection circuit works by detecting when the modulator output data has not changed state for at least 25 clock cycles in a row, indicating that the input signal is near or beyond full-scale, positive or negative. Typical response time to over-range signals is less than 3s. The over-range circuit actually begins to indicate an overrange condition when the magnitude of the input signal exceeds approximately 250 mV; it starts to generate periodic short pulses on OVR1, which get longer and more frequent as the input signal approaches full scale. The OVR1 output stays high continuously when the input is beyond full-scale. The over-range detection circuit continuously monitors channel 1 independent of which channel is selected with the CHAN signal. This allows continuous monitoring of channel 1 for faults while converting an input signal on channel 2. 11 Adjustable Threshold Detection The adjustable threshold detector causes the THR1 output to go high when the magnitude of the input signal on channel 1 exceeds a userdefined threshold level. The threshold level can be set to one of 16 different values between approximately 160 mV and 310 mV. The adjustable threshold detector uses a smaller version of the main conversion circuit in combination with a digital comparator to detect when the magnitude of the input signal on channel 1 is beyond the defined threshold level. As with the main conversion circuit, there is a trade-off between speed and resolution with the threshold detector; selecting faster detection times exhibit more noise as the signal passes through the threshold, while slower detection times offer lower noise. Both the detection time and threshold level are programmable using bits 2 through 7 of configuration register 2, as shown in Tables 5 and 6 below. As with the over-range detector, the adjustable threshold detector continuously monitors channel 1 independent of which channel is selected with the CHAN signal. This allows continuous monitoring of channel 1 for faults while converting Channel 2. Table 5. Threshold Detection Configuration. Threshold Detection Time 2 - 6 s 3 - 10 s 5 - 20 s 10 - 35 s Configuration Data Bits Bit 7 Low Low High High Bit 6 Low High Low High Notes: Bold italic type indicates Default values. Table 6. Threshold Level Configuration. Configuration Data Bits Threshold Level 160 mV 170 mV 180 mV 190 mV 200 mV 210 mV 220 mV 230 mV 240 mV 250 mV 260 mV 270 mV 280 mV 290 mV 300 mV 310 mV Notes: Bold italic type indicates Default values. Bit 5 Low Low Bit 4 Low Low Bit 3 Low Low High Bit 2 Low High Low High Low High Low High Low High High Low High High Low Low High High Low High Low High Low High Low High www.agilent.com/ semiconductors For product information and a complete list of distributors, please go to our web site. Data subject to change. Copyright (c) 2005 Agilent Technologies, Inc. February 2, 2005 Obsoletes 5989-1423EN 5989-2165EN |
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