SPI/I2C Compatible, Temperature Sensor, 4-Channel ADC and Quad Voltage Output DAC ADT7518 FEATURES APPLICATIONS Four 8-bit DACs Buffered voltage output Guaranteed monotonic by design over all codes 10-bit temperature-to-digital converter 10-bit 4-channel ADC DC input bandwidth Input range: 0 V to 2.25 V Temperature range: –40°C to +120°C Temperature sensor accuracy of typ: ±0.5°C Supply range: 2.7 V to 5.5 V DAC output range: 0 V to 2 VREF Power-down current: 1 µA Internal 2.25 VREF option Double-buffered input logic Buffered reference input Power-on reset to 0 V DAC output Simultaneous update of outputs (LDAC function) On-chip rail-to-rail output buffer amplifier Portable battery-powered instruments Personal computers Smart battery chargers Telecommunications systems Electronic text equipment Domestic appliances Process control PIN CONFIGURATION The ADT75181 combines a 10-bit temperature-to-digital converter, a 10-bit 4-channel ADC, and a quad 8-bit DAC, in a 16-lead QSOP package. The part also includes a band gap temperature sensor and a 10-bit ADC to monitor and digitize the temperature reading to a resolution of 0.25°C. The ADT7518 operates from a single 2.7 V to 5.5 V supply. The input voltage range on the ADC channels is 0 V to 2.25 V, and the input bandwidth is dc. The reference for the ADC channels is derived internally. The output voltage of the DAC ranges from 0 V to VDD, with an output voltage settling time of 7 ms typical. The ADT7518 provides two serial interface options: a 4-wire serial interface that is compatible with SPI, QSPI, MICROWIRE, and DSP interface standards, and a 2-wire SMBus/I2C interface. It features a standby mode that is controlled through the serial interface. 16 VOUT-C 15 VOUT-D VREF-IN 3 14 AIN4 CS 4 ADT7518 SCL/SCLK TOP VIEW 12 SDA/DIN (Not to Scale) 11 DOUT/ADD VDD 6 13 D+/AIN1 7 10 INT/INT D–/AIN2 8 9 LDAC/AIN3 04879-001 GND 5 Figure 1. SPI®, I2C®, QSPI™, MICROWIRE™, and DSP-compatible 4-wire serial interface SMBus packet error checking (PEC)-compatible 16-lead QSOP package GENERAL DESCRIPTION VOUT-B 1 VOUT-A 2 The reference for the four DACs is derived either internally or from a reference pin. The outputs of all DACs may be updated simultaneously using the software LDAC function or the external LDAC pin. The ADT7518 incorporates a power-on reset circuit, which ensures that the DAC output powers up to 0 V and remains there until a valid write takes place. The ADT7518’s wide supply voltage range, low supply current, and SPI-/I2C-compatible interface make it ideal for a variety of applications, including personal computers, office equipment, and domestic appliances. It is recommended that new designs use the ADT7519 rather than the ADT7518. The ADT7518’s internal and external temperature accuracy spec is only valid when not using the internal reference for the on-chip DAC. The ADT7519 does not have this limitation. 1 Protected by the following U.S. Patent Numbers: 6,169,442; 5,867,012; 5,764174. Other patents pending. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved. ADT7518 TABLE OF CONTENTS Specifications..................................................................................... 3 Conversion Speed....................................................................... 17 DAC AC Characteristics.............................................................. 6 Function Description—Voltage Output.................................. 18 Functional Block Diagram .............................................................. 7 Functional Description—Analog Inputs................................. 20 Absolute Maximum Ratings............................................................ 8 ADC Transfer Function............................................................. 21 ESD Caution.................................................................................. 8 Functional Description—Measurement.................................. 22 Pin Configuration and Functional Descriptions.......................... 9 ADT7518 Registers .................................................................... 25 Terminology .................................................................................... 10 Serial Interface ............................................................................ 33 Typical Performance Characteristics ........................................... 12 SMBus Alert Response............................................................... 38 Theory of Operation ...................................................................... 17 Outline Dimensions ....................................................................... 40 Power-Up Calibration................................................................ 17 Ordering Guide .......................................................................... 40 REVISION HISTORY 8/04—Data Sheet Changed from Rev. 0 to Rev. A Updated Format...................................................................... Universal Separate ADT7518 from ADT7516/ADT7517/ADT7518 Data Sheet........................ Universal Change to Equation.............................................................................25 7/03—Revision 0: Initial Version Rev. A | Page 2 of 40 ADT7518 SPECIFICATIONS Table 1. Temperature range is as follows: A version: –40°C to +120°C. VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.25 V, unless otherwise noted. Parameter1 DAC DC PERFORMANCE2,3 Resolution Relative Accuracy Differential Nonlinearity Offset Error Gain Error Lower Deadband Min Upper Deadband Offset Error Drift4 Gain Error Drift4 DC Power Supply Rejection Ratio4 DC Crosstalk4 ADC DC ACCURACY Resolution Total Unadjusted Error (TUE) Offset Error Gain Error ADC BANDWIDTH ANALOG INPUTS5 Input Voltage Range Max Unit 8 ±0.15 ±0.02 ±0.4 ±0.3 20 ±1 ±0.25 ±2 ±2 65 Bits LSB LSB % of FSR % of FSR mV 60 100 mV –12 –5 –60 200 2 0 0 DC Leakage Current Input Capacitance Input Resistance THERMAL CHARACTERISTICS6 INTERNAL TEMPERATURE SENSOR Accuracy @ VDD = 3.3 V ±10% 5 10 ppm of FSR/°C ppm of FSR/°C dB µV 10 3 ±0.5 ±2 DC Bits % of FSR % of FSR % of FSR Hz 2.25 VDD ±1 20 V V µA pF MΩ Conditions/Comments Guaranteed monotonic over all codes. Lower deadband exists only if offset error is negative. See Figure 8. Upper deadband exists if VREF = VDD and offset plus gain error is positive. See Figure 9. ∆VDD = ±10%. See Figure 5. Max VDD = 5 V. AIN1 to AIN4. C4 = 0 in Control Configuration 3. AIN1 to AIN4. C4 = 0 in Control Configuration 3. Internal reference used. Averaging on. ±0.5 ±2 ±2 ±3 Accuracy @ VDD = 5 V ±5% Resolution Long-Term Drift THERMAL CHARACTERISTICS6 EXTERNAL TEMPERATURE SENSOR Accuracy @ VDD = 3.3 V ± 10% ±1.5 ±3 ±5 ±3 ±5 10 °C °C °C °C °C Bits °C TA = 85°C. TA= 0°C to +85°C. TA = –40°C to +120°C. TA = 0°C to +85°C. TA = –40°C to +120°C. Equivalent to 0.25°C. Drift over 10 years if part is operated at 55°C. External transistor = 2N3906. ±1.5 ±3 ±5 ±3 ±5 10 °C °C °C °C °C Bits µA µA TA = 85°C. TA = 0°C to +85°C. TA = –40°C to +120°C. TA = 0°C to +85°C. TA = –40°C to +120°C. Equivalent to 0.25°C. High Level. Low Level. 0.25 Accuracy @ VDD = 5 V ± 5% ±2 ±3 Resolution Output Source Current THERMAL CHARACTERISTICS6 Thermal Voltage Output 8-Bit DAC Output Resolution Typ 180 11 1 °C Rev. A | Page 3 of 40 ADT7518 Parameter1 Scale Factor Min CONVERSION TIMES Slow ADC VDD/AIN Internal Temperature External Temperature Fast ADC VDD/AIN Internal Temperature External Temperature Typ 8.97 17.58 Max Unit mV/°C mV/°C Conditions/Comments 0 V to VREF output. TA = –40°C to +120°C. 0 V to 2 VREF output. TA = –40°C to +120°C. Single channel mode. 11.4 712 11.4 712 24.22 1.51 ms µs ms µs ms ms Averaging (16 samples) on. Averaging off. Averaging (16 samples) on. Averaging off. Averaging (16 samples) on. Averaging off. 712 44.5 2.14 134 14.25 890 µs µs ms µs ms µs Averaging (16 samples) on. Averaging off. Averaging (16 samples) on. Averaging off. Averaging (16 samples) on. Averaging off. Time to complete one measurement cycle through all channels. 79.8 4.99 94.76 9.26 ms ms ms ms AIN1 and AIN2 are selected on Pins 7 and 8. AIN1 and AIN2 are selected on Pins 7 and 8. D+ and D– are selected on Pins 7 and 8. D+ and D– are selected on Pins 7 and 8. 6.41 400.84 21.77 3.07 ms µs ms ms AIN1 and AIN2 are selected on Pins 7 and 8. AIN1 and AIN2 are selected on Pins 7 and 8. D+ and D– are selected on Pins 7 and 8. D+ and D– are selected on Pins 7 and 8. >10 –90 –75 V MΩ dB dB Buffered reference. Buffered reference and power-down mode. Frequency = 10 kHz. Frequency = 10 kHz. 2.25 80 V ppm/°C ROUND ROBIN UPDATE RATE5 Slow ADC @ 25°C Averaging On Averaging Off Averaging On Averaging Off Fast ADC @ 25°C Averaging On Averaging Off Averaging On Averaging Off DAC EXTERNAL REFERENCE INPUT4 VREF Input Range VREF Input Impedance Reference Feedthrough Channel-to-Channel Isolation ON-CHIP REFERENCE Reference Voltage4 Temperature Coefficient4 OUTPUT CHARACTERISTICS4 Output Voltage 7 1 0.001 DC Output Impedance Short-Circuit Current LDAC Pulse Width VDD − 0.1 0.5 25 16 2.5 5 Power-Up Time DIGITAL INPUTS4 Input Current VIL, Input Low Voltage VIH, Input High Voltage Pin Capacitance SCL, SDA Glitch Rejection VDD Ω mA mA µs µs ±1 0.8 1.89 3 20 V 10 50 µA V V pF ns ns Rev. A | Page 4 of 40 This is a measure of the minimum and maximum drive capability of the output amplifier. VDD = 5 V. VDD = 3 V. Coming out of power-down mode. VDD = 5 V. Coming out of power-down mode. VDD = 3.3 V. VIN = 0 V to VDD. All digital inputs. Input filtering suppresses noise spikes of less than 50 ns. Edge triggered input. ADT7518 Parameter1 DIGITAL OUTPUT Digital High Voltage, VOH Output Low Voltage, VOL Output High Current, IOH Output Capacitance, COUT INT/INT Output Saturation Voltage I2C TIMING CHARACTERISTICS 8, 9 Serial Clock Period, t1 Data In Setup Time to SCL High, t2 Data Out Stable after SCL Low, t3 SDA Low Setup Time to SCL Low (Start Condition), t4 SDA High Hold Time after SCL High (Stop Condition), t5 SDA and SCL Fall Time, t6 SPI TIMING CHARACTERISTICS4, 10 CS to SCLK Setup Time, t1 SCLK High Pulse Width, t2 SCLK Low Pulse Width, t3 Data Access Time after SCLK Falling Edge, t4 11 Data Setup Time Prior to SCLK Rising Edge, t5 Data Hold Time after SCLK Rising Edge, t6 CS to SCLK Hold Time, t7 CS to DOUT High Impedance, t8 POWER REQUIREMENTS VDD VDD Settling Time IDD (Normal Mode) 12 Min Typ Max Unit Conditions/Comments 0.4 1 50 0.8 V V mA pF V ISOURCE = ISINK = 200 µA. IOL = 3 mA. VOH = 5 V. 2.5 50 0 50 µs ns ns ns Fast Mode I2C. See Figure 2. 50 ns See Figure 2. 90 ns See Figure 2. See Figure 3. See Figure 3. See Figure 3. 35 ns ns ns ns 20 ns See Figure 3. 0 ns See Figure 3. 40 µs ns See Figure 3. See Figure 3. 5.5 50 3 3 10 10 10 33 V ms mA mA µA µA mW µW VDD settles to within 10% of its final voltage level. VDD = 3.3 V, VIH = VDD, and VIL = GND. VDD = 5 V, VIH = VDD, and VIL = GND. VDD = 3.3 V, VIH = VDD, and VIL = GND. VDD = 5 V, VIH = VDD, and VIL = GND. VDD = 3.3 V. Normal mode. VDD = 3.3 V. Shutdown mode. 2.4 0 50 50 0 2.7 2.2 IDD (Power-Down Mode) Power Dissipation 1 IOUT = 4 mA. See Figure 2. See Figure 2. See the Terminology section. DC specifications are tested with the outputs unloaded. Linearity is tested using a reduced code range: ADT7518 (Code 8 to 255). 4 Guaranteed by design and characterization, not production tested. 5 Round robin is the continuous sequential measurement of the following channels: VDD, internal temperature, external temperature (AIN1, AIN2), AIN3, and AIN4. 6 The temperature accuracy specifications are valid when the internal reference is not being used by the on-chip DAC. For new designs, the ADT7519 is recommended as it does not have this limitation. 7 For the amplifier output to reach its minimum voltage, the offset error must be negative. For the amplifier output to reach its maximum voltage (VREF = VDD), the offset plus gain error must be positive. 8 The SDA and SCL timing is measured with the input filters turned on to meet the fast-mode I2C specification. Switching off the input filters improves the transfer rate but has a negative effect on the EMC behavior of the part. 9 Guaranteed by design, not production tested. 10 All input signals are specified with tr = tf = 5 ns (10% to 90% of VDD), and timed from a voltage level of 1.6 V. 11 Measured with the load circuit shown in Figure 4. 12 The IDD specification is valid for all DAC codes and full-scale analog input voltages. Interface inactive. All DACs and ADCs active. Load currents excluded. 2 3 Rev. A | Page 5 of 40 ADT7518 DAC AC CHARACTERISTICS1 Table 2. VDD = 2.7 V to 5.5 V, RL = 4.7 kΩ to GND; CL = 200 pF to GND; 4.7 kΩ to VDD; all specifications TMIN to TMAX, unless otherwise noted. Parameter2 Output Voltage Settling Time ADT7518 Slew Rate Major-Code Change Glitch Energy Digital Feedthrough Digital Crosstalk Analog Crosstalk DAC-to-DAC Crosstalk Multiplying Bandwidth Total Harmonic Distortion Min Typ3 Max Unit 6 0.7 12 0.5 1 0.5 3 200 –70 8 µs V/µs nV-s nV-s nV-s nV-s nV-s kHz dB Conditions/Comments VREF = VDD = 5 V 1/4 scale to 3/4 scale change (40h to C0h) 1 LSB change around major carry VREF = 2 V ±0.1 V p-p VREF = 2.5 V ±0.1 V p-p. Frequency = 10 kHz. 1 Guaranteed by design and characterization, not production tested. See the Terminology section. 3 @ 25°C. 2 t1 SCL t5 t2 t4 SDA DATA IN t3 04879-002 SDA DATA OUT t6 Figure 2. I2C Bus Timing Diagram CS t1 t2 t7 SCLK DIN D7 D6 D5 t6 t5 D4 D3 D2 D1 t8 D0 X X X X X X X X D5 D4 D3 D2 D1 D0 t4 X X X X X X X D7 D6 Figure 3. SPI Bus Timing Diagram 200µA TO OUTPUT PIN IOL 1.6V CL 50pF 200µA 04879-004 X IOH Figure 4. Load Circuit for Access Time and Bus Relinquish Time VDD 4.7kΩ TO DAC OUTPUT 4.7kΩ 200pF 04879-005 DOUT Figure 5. Load Circuit for DAC Outputs Rev. A | Page 6 of 40 04879-003 t3 ADT7518 FUNCTIONAL BLOCK DIAGRAM INTERNAL TEMPERATURE VALUE REGISTER EXTERNAL TEMPERATURE VALUE REGISTER LIMIT COMPARATOR AIN4 14 TLOW LIMIT REGISTERS VCC LIMIT REGISTERS AINHIGH LIMIT REGISTERS AINLOW LIMIT REGISTERS VDD CONTROL CONFIG. 1 VALUE REGISTER REGISTER AIN1 CONTROL CONFIG. 2 VALUE REGISTER VDD SENSOR REGISTER AIN2 CONTROL CONFIG. 3 VALUE REGISTER DAC A REGISTERS STRING DAC A 2 VOUT-A DAC B REGISTERS STRING DAC B 1 VOUT-B DAC C REGISTERS STRING DAC C 16 VOUT-C DAC D REGISTERS STRING DAC D 15 VOUT-D 10 INT/INT REGISTER AIN3 GAIN SELECT LOGIC DAC CONFIGURATION REGISTERS VALUE REGISTER AIN4 POWERDOWN LOGIC LDAC CONFIGURATION REGISTERS VALUE REGISTER INTERRUPT MASK REGISTERS STATUS REGISTERS INTERNAL REFERENCE SPI/SMBus INTERFACE 6 5 4 13 12 11 9 3 VDD GND CS SCL SDA ADD LDAC/AIN3 VREF-IN Figure 6. Rev. A | Page 7 of 40 04879-006 LDAC/AIN3 9 A-TO-D CONVERTER ANALOG MUX THIGH LIMIT REGISTERS DIGITAL MUX D+/AIN1 7 D–/AIN2 8 ADT7518 ADDRESS POINTER REGISTER DIGITAL MUX ON-CHIP TEMPERATURE SENSOR ADT7518 ABSOLUTE MAXIMUM RATINGS Table 4. I2C Address Selection Table 3. Parameter VDD to GND Analog Input Voltage to GND Digital Input Voltage to GND Digital Output Voltage to GND Reference Input Voltage to GND Operating Temperature Range Storage Temperature Range Junction Temperature 16-Lead QSOP Package Power Dissipation1 Thermal Impedance2 θJA Junction-to-Ambient θJC Junction-to-Case IR Reflow Soldering Peak Temperature Time at Peak Temperature Ramp-Up Rate Ramp-Down Rate Rating –0.3 V to +7 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V –40°C to +120°C –65°C to +150°C 150°C (TJ max – TA)/θJA 105.44°C/W 38.8°C/W 220°C (0°C/5°C) 10 sec to 20 sec 2°C/sec to 3°C/sec –6°C/sec ADD Pin Low Float High I2C Address 1001 000 1001 010 1001 011 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1 2 Values relate to package being used on a 4-layer board. Junction-to-case resistance is applicable to components featuring a preferential flow direction, e.g., components mounted on a heat sink. Junction-to-ambient resistance is more useful for air cooled PCB-mounted components. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. A | Page 8 of 40 ADT7518 PIN CONFIGURATION AND FUNCTIONAL DESCRIPTIONS VOUT-B 1 16 VOUT-C VOUT-A 2 15 VOUT-D VREF-IN 3 CS 4 14 AIN4 ADT7518 13 SCL/SCLK TOP VIEW 12 SDA/DIN (Not to Scale) 11 DOUT/ADD VDD 6 D+/AIN1 7 10 INT/INT D–/AIN2 8 9 LDAC/AIN3 04879-007 GND 5 Figure 7. Pin Configuration QSOP Table 5. Pin Function Descriptions Pin No. 1 2 3 4 Mnemonic VOUT-B VOUT-A VREF-IN CS 5 6 7 GND VDD D+/AIN1 8 D–/AIN2 9 LDAC/AIN3 10 INT/INT 11 DOUT/ADD 12 SDA/DIN 13 SCL/SCLK 14 15 16 AIN4 VOUT-D VOUT-C Description Buffered Analog Output Voltage from DAC B. The output amplifier has rail-to-rail operation. Buffered Analog Output Voltage from DAC A. The output amplifier has rail-to-rail operation. Reference Input Pin for All Four DACs. This input is buffered and has an input range from 1 V to VDD. SPI Active Low Control Input. This is the frame synchronization signal for the input data. When CS goes low, it enables the input register, and data is transferred in on the rising edges and out on the falling edges of the subsequent serial clocks. It is recommended that this pin be tied high to VDD when operating the serial interface in I2C mode. Ground Reference Point for All Circuitry on the Part. Analog and digital ground. Positive Supply Voltage, 2.7 V to 5.5 V. The supply should be decoupled to ground. D+. Positive Connection to External Temperature Sensor. AIN1. Analog Input. Single-ended analog input channel. Input range is 0 V to 2.25 V or 0 V to VDD. D–. Negative Connection to External Temperature Sensor. AIN2. Analog Input. Single-ended analog input channel. Input range is 0 V to 2.25 V or 0 V to VDD. LDAC. Active Low Control Input. Transfers the contents of the input registers to their respective DAC registers. A falling edge on this pin forces any or all DAC registers to be updated if the input registers have new data. A minimum pulse width of 20 ns must be applied to the LDAC pin to ensure proper loading of a DAC register. This allows simultaneous update of all DAC outputs. Bit C3 of the Control Configuration 3 register enables the LDAC pin. Default is with the LDAC pin controlling the loading of the DAC registers. AIN3. Analog Input. Single-ended analog input channel. Input range is 0 V to 2.25 V or 0 V to VDD. Over Limit Interrupt. The output polarity of this pin can be set to give an active low or active high interrupt when temperature,VDD, or AIN limits are exceeded. The default is active low. Open-drain output—needs a pull-up resistor. SPI Serial Data Output. Logic output. Data is clocked out of any register at this pin. Data is clocked out on the falling edge of SCLK. Open-drain output—needs a pull-up resistor. ADD. I2C Serial Bus Address Selection Pin. Logic input. A low on this pin gives the address 1001 000; leaving it floating gives the address 1001 010; and setting it high gives the address 1001 011. The I2C address set up by the ADD pin is not latched by the device until after this address has been sent twice. On the eighth SCL cycle of the second valid communication, the serial bus address is latched in. Any subsequent changes on this pin will have no effect on the I2C serial bus address. SDA. I2C Serial Data Input/Output. I2C serial data to be loaded into the part’s registers and read from these registers is provided on this pin. Open-drain configuration—needs a pull-up resistor. DIN. SPI Serial Data Input. Serial data to be loaded into the part’s registers is provided on this pin. Data is clocked into a register on the rising edge of SCLK. Open-drain configuration—needs a pull-up resistor. Serial Clock Input. This is the clock input for the serial port. The serial clock is used to clock data out of any register of the ADT7518 and also to clock data into any register that can be written to. Open-drain configuration—needs a pullup resistor. Analog Input. Single-ended analog input channel. Input range is 0 V to 2.25 V or 0 V to VDD. Buffered Analog Output Voltage from DAC D. The output amplifier has rail-to-rail operation. Buffered Analog Output Voltage from DAC C. The output amplifier has rail-to-rail operation. Rev. A | Page 9 of 40 ADT7518 TERMINOLOGY Relative Accuracy increase in rates of reaction within the semiconductor material. Relative accuracy or integral nonlinearity (INL) is a measure of the maximum deviation, in LSBs, from a straight line passing through the endpoints of the transfer function. Typical INL versus code plots can be seen in Figure 10, Figure 11, and Figure 12. DC Power Supply Rejection Ratio (PSRR) This indicates how the output of the DAC is affected by changes in the supply voltage. PSRR is the ratio of the change in VOUT to a change in VDD for full-scale output of the DAC. It is measured in dB. VREF is held at 2 V and VDD is varied ±10%. Differential Nonlinearity DC Crosstalk Differential nonlinearity (DNL) is the difference between the measured change and the ideal 1 LSB change between any two adjacent codes. A specified differential nonlinearity of ±0.9 LSB maximum ensures monotonicity. Typical DAC DNL versus code plots can be seen in Figure 13, Figure 14, and Figure 15. This is the dc change in the output level of one DAC in response to a change in the output of another DAC. It is measured with a full-scale output change on one DAC while monitoring another DAC. It is expressed in µV. Total Unadjusted Error (TUE) Total unadjusted error is a comprehensive specification that includes the sum of the relative accuracy error, gain error, and offset error under a specified set of conditions. Offset Error This is a measure of the offset error of the DAC and the output amplifier (see Figure 8 and Figure 9). It can be negative or positive, and it is expressed in mV. Offset Error Match Reference Feedthrough This is the ratio of the amplitude of the signal at the DAC output to the reference input when the DAC output is not being updated (i.e., LDAC is high). It is expressed in dB. Channel-to-Channel Isolation This is the ratio of the amplitude of the signal at the output of one DAC to a sine wave on the reference input of another DAC. It is measured in dB. Major-Code Transition Glitch Energy This is a measure of the span error of the DAC. It is the deviation in slope of the actual DAC transfer characteristic from the ideal expressed as a percentage of the full-scale range. Major-code transition glitch energy is the energy of the impulse injected into the analog output when the code in the DAC register changes state. It is normally specified as the area of the glitch in nV-s and is measured when the digital code is changed by 1 LSB at the major carry transition (011...1 to 100...00 or 100...00 to 011...11). Gain Error Match Digital Feedthrough This is the difference in gain error between any two channels. This is a measure of the change in offset error with changes in temperature. It is expressed in (ppm of full-scale range)/°C. Digital feedthrough is a measure of the impulse injected into the analog output of a DAC from the digital input pins of the device but is measured when the DAC is not being written to. It is specified in nV-s and is measured with a full-scale change on the digital input pins, i.e., from all 0s to all 1s or vice versa. Gain Error Drift Digital Crosstalk This is a measure of the change in gain error with changes in temperature. It is expressed in (ppm of full-scale range)/°C. This is the glitch impulse transferred to the output of one DAC at midscale in response to a full-scale code change (all 0s to all 1s and vice versa) in the input register of another DAC. It is measured in standalone mode and is expressed in nV-s. This is the difference in offset error between any two channels. Gain Error Offset Error Drift Long Term Temperature Drift This is a measure of the change in temperature error over time. It is expressed in °C. The concept of long-term stability has been used for many years to describe the amount an IC’s parameter shifts during its lifetime. This is a concept that has typically been applied to both voltage references and monolithic temperature sensors. Unfortunately, integrated circuits cannot be evaluated at room temperature (25°C) for 10 years or so to determine this shift. Manufacturers perform accelerated lifetime testing of integrated circuits by operating ICs at elevated temperatures (between 125°C and 150°C) over a shorter period (typically between 500 and 1,000 hours). As a result, the lifetime of an integrated circuit is significantly accelerated due to the Analog Crosstalk This is the glitch impulse transferred to the output of one DAC due to a change in the output of another DAC. It is measured by loading one of the input registers with a full-scale code change (all 0s to all 1s and vice versa) while keeping LDAC high. Then pulse LDAC low and monitor the output of the DAC whose digital code was not changed. The area of the glitch is expressed in nV-s. Rev. A | Page 10 of 40 ADT7518 DAC-to-DAC Crosstalk Multiplying Bandwidth The amplifiers within the DAC have a finite bandwidth. The multiplying bandwidth is a measure of this. A sine wave on the reference (with full-scale code loaded to the DAC) appears on the output. The multiplying bandwidth is the frequency at which the output amplitude falls to 3 dB below the input. GAIN ERROR + OFFSET ERROR OUTPUT VOLTAGE NEGATIVE OFFSET ERROR ACTUAL IDEAL LOWER DEADBAND CODES Total Harmonic Distortion This is the difference between an ideal sine wave and its attenuated version using the DAC. The sine wave is used as the reference for the DAC, and the THD is a measure of the harmonics present on the DAC output, expressed in dB. DAC CODE AMPLIFIER FOOTROOM NEGATIVE OFFSET ERROR 04879-008 This is the glitch impulse transferred to the output of one DAC due to a digital code change and subsequent output change of another DAC. This includes both digital and analog crosstalk. It is measured by loading one of the DACs with a full-scale code change (all 0s to all 1s and vice versa) with LDAC low and monitoring the output of another DAC. The energy of the glitch is expressed in nV-s. Round Robin This term is used to describe the ADT7518 cycling through the available measurement channels in sequence, taking a measurement on each channel. Figure 8. DAC Transfer Function with Negative Offset GAIN ERROR + OFFSET ERROR DAC Output Settling Time This is the time required, following a prescribed data change, for the output of a DAC to reach and remain within ±0.5 LSB of the final value. A typical prescribed change is from 1/4 scale to 3/4 scale. UPPER DEADBAND CODES OUTPUT VOLTAGE POSITIVE OFFSET ERROR DAC CODE FULL SCALE Figure 9. DAC Transfer Function with Positive Offset (VREF = VDD) Rev. A | Page 11 of 40 04879-009 ACTUAL IDEAL ADT7518 TYPICAL PERFORMANCE CHARACTERISTICS 0.14 0.20 INL WCP 0.12 0.15 0.10 0.10 INL WCN 0.05 ERROR (LSB) INL ERROR (LSB) 0.08 0 –0.05 0.06 0.04 DNL WCP 0.02 0 –0.10 –0.02 –0.20 0 50 100 150 200 DNL WCN 04879-013 04879-010 –0.15 –0.04 –0.06 –40 250 –10 20 80 110 Figure 13. ADT7518 DAC INL Error and DNL Error vs. Temperature Figure 10. ADT7518 Typical DAC INL Plot 0.10 0 0.08 –0.2 0.06 OFFSET ERROR –0.4 0.04 ERROR (LSB) –0.6 0.02 0 –0.02 –0.8 –1.0 –1.2 –0.04 –1.4 –0.06 –0.10 0 50 100 150 200 04879-014 04879-011 GAIN ERROR –0.08 –1.6 –1.8 –40 250 –20 0 20 40 60 80 100 120 TEMPERATURE (°C) DAC CODE Figure 14. DAC Offset Error and Gain Error vs. Temperature Figure 11. ADT7518 Typical DAC DNL Plot 10 0.30 0.25 OFFSET ERROR INL WCP 5 0.20 ERROR (LSB) 0 0.15 0.10 0.05 DNL WCP VREF = 2.25V –5 –10 0 DNL WCN –0.10 1.0 1.5 2.0 2.5 3.0 3.5 4.0 GAIN ERROR –15 INL WCN 4.5 04879-015 –0.05 04879-012 ERROR (LSB) DNL ERROR (LSB) 50 TEMPERATURE (°C) DAC CODE –20 2.7 5.0 3.3 3.6 4.0 4.5 5.0 VDD (V) VREF (V) Figure 15. DAC Offset Error and Gain Error vs. VDD Figure 12. ADT7518 DAC INL and DNL Error vs, VREF Rev. A | Page 12 of 40 5.5 ADT7518 2.505 7 2.500 6 5 SOURCE CURRENT ICC (mA) 2.490 2.485 SINK CURRENT 3 2 VDD = 5V VREF = 5V DAC OUTPUT LOADED TO MIDSCALE 2.470 2.465 0 1 2 1 3 4 5 04879-019 2.475 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 VCC (V) 6 CURRENT (mA) Figure 19. Power-Down Current vs. Supply Voltage @ 25°C Figure 16. DAC VOUT Source and Sink Current Capability 4.0 0 –0.2 3.5 OFFSET ERROR –0.4 3.0 DAC OUTPUT (V) –0.6 –0.8 –1.0 –1.2 2.5 2.0 1.5 1.0 –1.4 GAIN ERROR –1.8 –40 0.5 04879-017 –1.6 –20 0 20 40 60 80 100 04879-020 ERROR (LSB) 4 2.480 04879-016 DAC OUTPUT (V) 2.495 0 0 120 2 4 TEMPERATURE (°C) 8 10 Figure 20. DAC Half-Scale Settling (1/4 to 3/4 Scale Code Change) Figure 17. Supply Current vs. DAC Code 2.00 1.8 ADC OFF DAC OUTPUTS AT 0V 1.6 1.95 DAC OUTPUT (V) 1.4 1.90 1.85 1.2 1.0 0.8 0.6 04879-021 0.4 1.80 04879-018 ICC (mA) 6 TIME (µs) 0.2 0 1.75 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 VCC (V) 0 2 4 6 8 TIME (µs) Figure 18. Supply Current vs. Supply Voltage @ 25°C Figure 21. Exiting Power-Down to Midscale Rev. A | Page 13 of 40 10 ADT7518 0.4700 2.329 VDD = 5V VREF = 5V DAC OUTPUT LOADED TO MIDSCALE 0.4695 2.328 0.4690 2.327 DAC OUTPUT (V) DAC OUTPUT (V) 0.4685 0.4680 0.4675 0.4670 0.4665 2.326 2.325 2.324 0.4660 0.4650 0 2 4 6 8 04879-025 2.323 04879-022 0.4655 2.322 10 0 1 2 TIME (µs) Figure 22. ADT7518 DAC Major Code Transition Glitch Energy; 0...11 to 100...00 1.0 0.4725 0.8 5 0.6 0.4720 0.4 INL ERROR (LSB) 0.4715 0.4710 0.4705 0.4700 0.2 0 –0.2 –0.4 0.4695 0.4690 0.4685 0 2 4 6 8 04879-026 04879-023 –0.6 –0.8 –1.0 0 10 TIME (µs) 200 400 600 ADC CODE 800 1000 Figure 26. ADC INL with Ref = VDD (3.3 V) Figure 23. ADT7518 DAC Major Code Transition Glitch Energy; 100…00 to 011…11 0 0 VDD = 5V TA = 25°C –10 –4 –20 –6 –30 –8 –40 –10 –50 –12 1 2 3 4 ±100mV RIPPLE ON VCC VREF = 2.25V VDD = 3.3V TEMPERATURE = 25°C 04879-027 AC PSRR (dB) –2 04879-024 DAC OUTPUT (V) 4 Figure 25. DAC-to-DAC Crosstalk 0.4730 FULL-SCALE ERROR (mV) 3 TIME (µs) –60 5 1 VREF (V) 10 FREQUENCY (kHz) Figure 27. PSRR vs. Supply Ripple Frequency Figure 24. DAC Full-Scale Error vs. VREF Rev. A | Page 14 of 40 100 ADT7518 15 1.5 VDD = 3.3V TEMPERATURE = 25°C EXTERNAL TEMPERATURE @ 5V 10 INTERNAL TEMPERATURE @ 3.3V TEMPERATURE ERROR (°C) 0.5 0 –0.5 –1.0 –30 0 40 85 TEMPERATURE (°C) D+ TO GND 0 –5 D+ TO VCC –10 –15 04879-031 EXTERNAL TEMPERATURE @ 3.3V INTERNAL TEMPERATURE @ 5V 5 –20 04879-028 TEMPERATURE ERROR (°C) 1.0 –25 120 0 10 20 30 40 50 60 70 Figure 28. Internal Temperature Error @ 3.3 V and 5 V VDD = 3.3V 2 –10 TEMPERATURE ERROR (°C) OFFSET ERROR 1 0 –1 GAIN ERROR –2 –20 –30 –40 –50 04879-029 –3 –20 0 20 40 60 TEMPERATURE (°C) 80 100 04879-032 ERROR (LSB) 100 0 VDD = 3.3V –60 0 120 5 10 15 20 25 30 35 40 45 50 CAPACITANCE (nF) Figure 29. ADC Offset Error and Gain Error vs. Temperature Figure 32. External Temperature Error vs. Capacitance between D+ and D– 3 10 OFFSET ERROR VDD = 3.3V COMMON-MODE VOLTAGE = 100mV 8 TEMPERATURE ERROR (°C) 2 1 0 –1 6 4 2 0 –2 –2 –3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 –4 –6 5.5 1 VDD (V) Figure 30. ADC Offset Error and Gain Error vs. VDD 04879-033 GAIN ERROR 04879-030 ERROR (LSB) 90 Figure 31. External Temperature Error vs. PCB Leakage Resistance 3 –4 –40 80 PCB LEAKAGE RESISTANCE (MΩ) 100 200 300 400 NOISE FREQUENCY (Hz) 500 600 Figure 33. External Temperature Error vs. Common-Mode Noise Frequency Rev. A | Page 15 of 40 ADT7518 70 140 60 120 50 TEMPERATURE (°C) 40 30 20 100 INTERNAL TEMPERATURE 80 60 40 10 –10 1 100 200 300 400 NOISE FREQUENCY (MHz) 500 TEMPERATURE OF ENVIRONMENT CHANGED HERE 20 04879-034 0 0 600 Figure 34. External Temperature Error vs. Differential-Mode Noise Frequency 0 10 20 30 TIME (s) 04879-036 TEMPERATURE ERROR (°C) EXTERNAL TEMPERATURE VDD = 3.3V DIFFERENTIAL-MODE VOLTAGE = 100mV 40 50 60 Figure 36. Temperature Sensor Response to Thermal Shock 0.6 0 VDD = 3.3V –5 ATTENUATION (dB) 0.2 0 –0.2 –10 –15 ±250mV –20 –0.6 04879-035 –0.4 1 100 200 300 400 NOISE FREQUENCY (Hz) 500 04879-037 TEMPERATURE ERROR (°C) 0.4 –25 600 1 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) Figure 35. Internal Temperature Error vs. Power Supply Noise Frequency Figure 37. DAC Multiplying Bandwidth (Small Signal Frequency Response) Rev. A | Page 16 of 40 ADT7518 THEORY OF OPERATION Directly after the power-up calibration routine, the ADT7518 goes into idle mode. In this mode, the device is not performing any measurements and is fully powered up. All four DAC outputs are at 0 V. To begin monitoring, write to the Control Configuration 1 register (Address 18h) and set Bit C0 = 1. The ADT7518 goes into its power-up default measurement mode, which is round robin. The device then to take measurements on the VDD channel, internal temperature sensor channel, external temperature sensor channel, or AIN1 and AIN2, AIN3, and finally AIN4. Once it finishes taking measurements on the AIN4 channel, the device immediately loops back to start taking measurements on the VDD channel and repeats the same cycle as before. This loop continues until the monitoring is stopped by resetting Bit C0 of the Control Configuration 1 register to 0. It is also possible to continue monitoring as well as switching to single-channel mode by writing to the Control Configuration 2 register (Address 19h) and setting Bit C4 = 1. Further explanation of the single-channel and round robin measurement modes is given in later sections. All measurement channels have averaging enabled on them on power-up. Averaging forces the device to take an average of 16 readings before giving a final measured result. To disable averaging and consequently decrease the conversion time by a factor of 16, set Bit C5 = 1 in the Control Configuration 2 register. There are four single-ended analog input channels on the ADT7518: AIN1 to AIN4. AIN1 and AIN2 are multiplexed with the external temperature sensor terminals D+ and D–. Bits C1 and C2 of the Control Configuration 1 register (Address 18h) are used to select between AIN1/AIN2 and the external temperature sensor. The input range on the analog input channels is dependent on whether the ADC reference used is the internal VREF or VDD. To meet linearity specifications, it is recommended that the maximum VDD value is 5 V. Bit C4 of the Control Configuration 3 register is used to select between the internal reference or VDD as the analog inputs’ ADC reference. Controlling the DAC outputs can be done by writing to the DACs’ MSB and LSB registers (Addresses 10h to 17h). The power-up default setting is to have a low going pulse on the LDAC pin (Pin 9) controlling the updating of the DAC outputs from the DAC registers. Alternatively, one can configure the updating of the DAC outputs to be controlled by means other than the LDAC pin by setting Bit C3 = 1 of the Control Configuration 3 register (Address 1Ah). The DAC Configuration register (Address 1Bh) and the LDAC Configuration register (Address 1Ch) can now be used to control the DAC updating. These two registers also control the output range of the DACs and selecting between the internal or external reference. DAC A and DAC B outputs can be configured to give a voltage output proportional to the temperature of the internal and external temperature sensors, respectively. The dual serial interface defaults to the I2C protocol on powerup. To select and lock in the SPI protocol, follow the selection process as described in the Serial Interface Selection section. The I2C protocol cannot be locked in, while the SPI protocol is automatically locked in on selection. The interface can be switched back to be I2C on selection when the device is powered off and on. When using I2C, the CS pin should be tied to either VDD or GND. There are a number of different operating modes on the ADT7518 devices and all of them can be controlled by the configuration registers. These features consist of enabling and disabling interrupts, polarity of the INT/INT pin, enabling and disabling the averaging on the measurement channels SMBus timeout and software reset. POWER-UP CALIBRATION It is recommended that no communication to the part be initiated until approximately 5 ms after VDD has settled to within 10% of its final value. It is generally accepted that most systems take a maximum of 50 ms to power up. Power-up time is directly related to the amount of decoupling on the voltage supply line. During the 5 ms after VDD has settled, the part is performing a calibration routine. Any communication to the device during calibration will interrupt this routine, and could cause erroneous temperature measurements. If it is not possible to have VDD at its nominal value by the time 50 ms has elapsed or if communication to the device has started prior to VDD settling, it is recommended that a measurement be taken on the VDD channel before a temperature measurement is taken. The VDD measurement is used to calibrate out any temperature measurement error due to different supply voltage values. CONVERSION SPEED The internal oscillator circuit used by the ADC has the capability to output two different clock frequencies. This means that the ADC is capable of running at two different speeds when doing a conversion on a measurement channel. Thus, the time taken to perform a conversion on a channel can be reduced by setting Bit C0 of the Control Configuration 3 register (Address 1Ah). This increases the ADC clock speed from 1.4 kHz to 22 kHz. At the higher clock speed, the analog filters on the D+ and D– input pins (external temperature sensor) are switched off. This is why the power-up default setting is to have the ADC working at the slow speed. The typical times for fast and slow ADC speeds are given in the specifications. Rev. A | Page 17 of 40 ADT7518 The ADT7518 powers up with averaging on. This means every channel is measured 16 times and internally averaged to reduce noise. The conversion time can also be sped up by turning off the averaging. This is done by setting Bit C5 of the Control Configuration 2 register (Address 19h) to 1. where: FUNCTION DESCRIPTION—VOLTAGE OUTPUT Resistor String Digital-to-Analog Converters The resistor string section is shown in Figure 39. It is simply a string of resistors, each of approximately 603 Ω. The digital code loaded to the DAC register determines at which node on the string the voltage is tapped off to be fed into the output amplifier. The voltage is tapped off by closing one of the switches connecting the string to the amplifier. Because it is a string of resistors, it is guaranteed monotonic. The ADT7518 operates from a single supply of 2.7 V to 5.5 V, and the output buffer amplifiers provide rail-to-rail output swing with a slew rate of 0.7 V/µs. All four DACs share a common reference input, VREF-IN. The reference input is buffered to draw virtually no current from the reference source because it offers the source a high impedance input. The devices have a power-down mode in which all DACs may be turned off completely with a high impedance output. Each DAC output will not be updated until it receives the LDAC command. Therefore, while the DAC registers would have been written to with a new value, this value will not be represented by a voltage output until the DACs have received the LDAC command. Reading back from any DAC register prior to issuing an LDAC command will result in the digital value that corresponds to the DAC output voltage. Thus, the digital value written to the DAC register cannot be read back until after the LDAC command has been initiated. This LDAC command can be given by either pulling the LDAC pin low (falling edge loads DACs), setting up Bits D4 and D5 of the DAC configuration register (Address 1Bh), or using the LDAC register (Address 1Ch). VREF-IN REFERENCE BUFFER INT VREF INPUT REGISTER DAC REGISTER GAIN MODE (GAIN = 1 OR 2) VOUT-A RESISTOR STRING OUTPUT BUFFER AMPLIFIER Figure 38. Single DAC Channel Architecture R R TO OUTPUT AMPLIFIER R R 04879-039 R When using the LDAC pin to control the DAC register loading, the low going pulse width should be 20 ns minimum. The LDAC pin has to go high and low again before the DAC registers can be reloaded. Figure 39. Resistor String VREF-IN Digital-to-Analog Section VOUT = VREF × D 2N 2.25V INTERNAL VREF STRING DAC A STRING DAC B STRING DAC C STRING DAC D 04879-040 The architecture of one DAC channel consists of a resistor string DAC followed by an output buffer amplifier. The voltage at the VREF-IN pin or the on-chip reference of 2.25 V provides the reference voltage for the corresponding DAC. Figure 38 shows a block diagram of the DAC architecture. Since the input coding to the DAC is straight binary, the ideal output voltage is given by Figure 40. DAC Reference Buffer Circuit Rev. A | Page 18 of 40 04879-038 The ADT7518 has four resistor string DACs fabricated on a CMOS process with resolutions of 12, 10, and 8 bits, respectively. They contain four output buffer amplifiers and are written to via I2C serial interface or SPI serial interface. See the Serial Interface section for more information. D = decimal equivalent of the binary code that is loaded to the DAC register: 0 to 255 for ADT7518 (8 bits) N = DAC resolution ADT7518 DAC Reference Inputs VREF and this can be increased to 0 V to 2 VREF. Increasing the output voltage span to 2 VREF can be done by setting D0 = 1 for DAC A (internal temperature sensor) and D1 = 1 for DAC B (external temperature sensor) in the DAC configuration register (Address 1Bh). There is an input reference pin for the DACs. This reference input is buffered (see Figure 40). The advantage with the buffered input is the high impedance it presents to the voltage source driving it. The user can have an external reference voltage as low as 1 V and as high as VDD. The restriction of 1 V is due to the footroom of the reference buffer. The output voltage is capable of tracking a maximum temperature range of –128°C to +127°C, but the default setting is –40°C to +127°C. If the output voltage range is 0 V to VREF-IN (VREF-IN = 2.25 V), then this corresponds to 0 V representing –40°C, and 1.48 V representing +127°C. This, of course, will give an upper deadband between 1.48 V and VREF. The LDAC configuration register controls the option to select between internal and external voltage references. The default setting is for external reference selected. Output Amplifier The internal and external analog temperature offset registers can be used to vary this upper deadband and, consequently, the temperature that 0 V corresponds to. Table 6 and Table 7 give examples of how this is done using a DAC output voltage span of VREF and 2 VREF, respectively. Simply write in the temperature value, in twos complement format, at which 0 V is to start. For example, if using the DAC A output and 0 V to start at –40°C, program D8h into the internal analog temperature offset register (Address 21h). This is an 8-bit register and has a temperature offset resolution of only 1°C for all device models. Use the formulas following the tables to determine the value to program into the offset registers. The output buffer amplifier can generate output voltages to within 1 mV of either rail. Its actual range depends on the value of VREF, gain, and offset error. If a gain of 1 is selected (Bits 0 to 3 of the DAC configuration register = 0), the output range is 0.001 V to VREF. If a gain of 2 is selected (Bits 0 to 3 of the DAC configuration register = 1), the output range is 0.001 V to 2 VREF. Because of clamping, however, the maximum output is limited to VDD − 0.001 V. The output amplifier can drive a load of 4.7 kΩ to GND or VDD, in parallel with 200 pF to GND or VDD (see Figure 5). The source and sink capabilities of the output amplifier can be seen in the plot of Figure 16. Table 6. Thermal Voltage Output (0 V to VREF) O/P Voltage (V) 0 0.5 1 1.12 1.47 1.5 2 2.25 The slew rate is 0.7 V/µs with a half-scale settling time to ±0.5 LSB (at 8 bits) of 6 µs. Thermal Voltage Output The ADT7518 can output voltages that are proportional to temperature. DAC A output can be configured to represent the temperature of the internal sensor while DAC B output can be configured to represent the external temperature sensor. Bits C5 and C6 of the Control Configuration 3 register select the temperature proportional output voltage. Each time a temperature measurement is taken, the DAC output is updated. The output resolution for the ADT7518 is 8 bits with a 1°C change corresponding to 1 LSB change. The default output range is 0 V to Default °C –40 +17 +73 +87 +127 Max °C –128 –71 –15 –1 +39 +42 +99 +127 UDB∗ UDB∗ UDB∗ ∗ Upper deadband has been reached. DAC output is not capable of increasing. See Figure 9. VDD I N×I IBIAS OPTIONAL CAPACITOR, UP TO 3nF MAX. CAN BE ADDED TO IMPROVE HIGH FREQUENCY NOISE REJECTION IN NOISY ENVIRONMENTS D+ VOUT+ C1 TO ADC D– LOW-PASS FILTER fC = 65kHz BIAS DIODE Figure 41. Signal Conditioning for External Diode Temperature Sensor Rev. A | Page 19 of 40 VOUT– 04879-041 REMOTE SENSING TRANSISTOR (2N3906) Sample °C 0 +56 +113 +127 UDB∗ UDB∗ UDB∗ UDB∗ ADT7518 VDD N×I I IBIAS VOUT+ TO ADC BIAS DIODE VOUT– 04879-042 INTERNAL SENSE TRANSISTOR Figure 42. Top Level Structure of Internal Temperature Sensor Example: Default °C –40 –26 +12 +3 +17 +23 +43 +45 +73 +88 +102 +116 UDB* UDB* UDB* UDB* UDB* UDB* UDB* Max °C –128 –114 –100 –85 –71 –65 –45 –43 –15 0 +14 +28 +42 +56 +70 +85 +99 +113 +127 Sample °C 0 +14 +28 +43 +57 +63 +83 +85 +113 +127 UDB* UDB* UDB* UDB* UDB* UDB* UDB* UDB* UDB* Offset Register Code (d) = 10d = 0Ah The following equation is used to work out the various temperatures for the corresponding 8-bit DAC output: 8 - Bit Temp = (DAC O / P ÷ 1 LSB) + (0 V Temp) For example, if the output is 1.5 V, VREF-IN = 2.25 V, 8-bit DAC has an LSB size = 2.25 V/256 = 8.79 x 10–3, and 0 V temperature is at –128°C, then the resultant temperature is (1.5 ÷ 8.79 ×10 −3 ) + (− 128) = +43°C Figure 43 shows a graph of the DAC output versus temperature for a VREF-IN = 2.25 V. 2.25 2.10 1.95 1.80 * Upper deadband has been reached. DAC output is not capable of increasing. See Figure 9. 58h + DB7(1) = D8h Positive temperatures: Offset Register Code (d) = 0 V Temp 0V = –40°C 1.20 1.05 0.90 0.75 0V = 0°C 0.30 0.15 0 –128–110 –90 –70 –50 –30 –10 10 30 50 TEMPERATURE (°C) where: D7 of Offset Register Code is set to 1 for negative temperatures. Since a negative temperature has been inserted into the equation, DB7 (MSB) of the offset register code is set to 1. Therefore 58h becomes D8h. 1.35 0.45 Offset Register Code(d ) = (0 V Temp) + 128 Offset Register Code(d ) = ( −40) + 128 = 88d = 58h 1.50 0.60 Negative temperatures: Example: 0V = –128°C 1.65 04879-043 O/P Voltage (V) 0 0.25 0.5 0.75 1 1.12 1.47 1.5 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 DAC OUTPUT (V) Table 7. Thermal Voltage Output (0 V to 2 VREF) 70 90 110 127 Figure 43. DAC Output vs. Temperature VREF-IN = 2.25 V FUNCTIONAL DESCRIPTION—ANALOG INPUTS Single-Ended Inputs The ADT7518 offers four single-ended analog input channels. The analog input range is from 0 V to 2.25 V, or 0 V to VDD. To maintain the linearity specification, it is recommended that the maximum VDD value be set at 5 V. Selection between the two input ranges is done by Bit C4 of the Control Configuration 3 register (Address 1Ah). Setting this bit to 0 sets up the analog input ADC reference to be sourced from the internal voltage reference of 2.25 V. Setting the bit to 1 sets up the ADC reference to be sourced from VDD. Rev. A | Page 20 of 40 ADT7518 The ADC resolution is 10 bits and is mostly suitable for dc input signals. Bits C1:2 of the Control Configuration 1 register (Address 18h) are used to set up Pins 7 and 8 as AIN1 and AIN2. Figure 44 shows the overall view of the 4-channel analog input path. 111...111 111...110 Figure 44. Quad Analog Input Path 111...000 011...111 1LSB = INT VREF/1024 1LSB = VDD/1024 Converter Operation The analog input channels use a successive approximation ADC based on a capacitor DAC. Figure 45 and Figure 46 show simplified schematics of the ADC. Figure 45 shows the ADC during acquisition phase. SW2 is closed and SW1 is in position A. The comparator is held in a balanced condition and the sampling capacitor acquires the signal on AIN. VDD INT VREF A CAP DAC AIN ACQUISITION PHASE SW2 CONTROL LOGIC REF/2 COMPARATOR Example: Internal reference used. Therefore VREF = 2.25 V. AIN value = 512d REF 1 LSB size = 2.25 V / 1024 = 2.197 × 10 −3 CAP DAC AIN B SW2 CONVERSION PHASE CONTROL LOGIC REF/2 COMPARATOR AIN voltage = 512 × 2.197 × 10 −3 = 1.125 V 04879-046 SW1 To work out the voltage on any analog input channel, the following method can be used: d = decimal VDD INT VREF SAMPLING CAPACITOR Figure 47. Single-Ended Transfer Function AIN voltage = AIN value(d ) × LSB size Figure 45. ADC Acquisition Phase A +VREF – 1LSB ANALOG INPUT Convert the value read back from the AIN value register into a decimal format. B 04879-045 SW1 0V 1/2LSB 1 LSB = reference (v)/1024 REF SAMPLING CAPACITOR 000...010 000...001 000...000 04879-047 AIN4 TO ADC VALUE REGISTER 10-BIT ADC ADC CODE AIN3 04879-044 AIN2 The output coding of the ADT7518 analog inputs is straight binary. The designed code transitions occur midway between successive integer LSB values (i.e., 1/2 LSB, 3/2 LSB). The LSB is VDD/1024 or internal VREF/1024, internal VREF = 2.25 V. The ideal transfer characteristic is shown in Figure 47. Analog Input ESD Protection Figure 46. ADC Conversion Phase When the ADC eventually goes into conversion phase (see Figure 46), SW2 opens and SW1 moves to position B, causing the comparator to become unbalanced. The control logic and the DAC are used to add and subtract fixed amounts of charge from the sampling capacitor to bring the comparator back into a balanced condition. When the comparator is rebalanced, the conversion is complete. The control logic generates the ADC output code. Figure 47 shows the ADC transfer function for the analog inputs. Figure 48 shows the input structure on any of the analog input pins that provides ESD protection. The diode provides the main ESD protection for the analog inputs. Care must be taken that the analog input signal never drops below the GND rail by more than 200 mV. If this happens, the diode will become forward-biased and start conducting current into the substrate. The 4 pF capacitor is the typical pin capacitance and the resistor is a lumped component made up of the on-resistance of the multiplexer switch. 100Ω AIN 4pF 04879-048 M U L T I P L E X E R AIN1 ADC TRANSFER FUNCTION Figure 48. Equivalent Analog Input ESD Circuit Rev. A | Page 21 of 40 ADT7518 S/W RESET INTERNAL TEMP INTERRUPT STATUS REGISTER (TEMP AND AIN1 TO AIN4) STATUS BITS EXTERNAL TEMP VDD WATCHDOG LIMIT COMPARISONS INTERRUPT MASK REGISTERS STATUS BIT INTERRUPT STATUS REGISTER 2 (VDD) AIN1–AIN4 INT/INT ENABLE BIT CONTROL CONFIGURATION REGISTER 1 04879-049 READ RESET INT/INT (LATCHED OUTPUT) DIODE FAULT Figure 49. Interrupt Structure AIN Interrupts The measured results from the AIN inputs are compared with the AIN VHIGH (greater than comparison) and VLOW (less than or equal to comparison) limits. An interrupt occurs if the AIN inputs exceed or equal the limit registers. These voltage limits are stored in on-chip registers. Note that the limit registers are 8 bits long while the AIN conversion result is 10 bits long. If the voltage limits are not masked out, then any out-of-limit comparisons generate flags that are stored in the Interrupt Status 1 register (Address = 00h) and one or more out-of-limit results will cause the INT/INT output to pull either high or low depending on the output polarity setting. It is good design practice to mask out interrupts for channels that are of no concern to the application. Figure 49 shows the interrupt structure for the ADT7518. It gives a block diagram representation of how the various measurement channels affect the INT/INT pin. FUNCTIONAL DESCRIPTION—MEASUREMENT Temperature Sensor The ADT7518 contains an ADC with special input signal conditioning to enable operation with external and on-chip diode temperature sensors. When the ADT7518 is operating in single-channel mode, the ADC continually processes the measurement taken on one channel only. This channel is preselected by Bits C0:C2 in the Control Configuration 2 register (Address 19h). When in round robin mode, the analog input multiplexer sequentially selects the VDD input channel, the on-chip temperature sensor to measure its internal temperature, either the external temperature sensor or AIN1 and AIN2, AIN3, and then AIN4. These signals are digitized by the ADC and the results are stored in the various value registers. The measured results from the temperature sensors are compared with the internal and external THIGH, TLOW limits. These temperature limits are stored in on-chip registers. If the temperature limits are not masked, any out-of-limit comparisons generate flags that are stored in the Interrupt Status 1 register. One or more out-of-limit results will cause the INT/INT output to pull either high or low depending on the output polarity setting. Theoretically, the temperature measuring circuit can measure temperatures from –128°C to +127°C with a resolution of 0.25°C. However, temperatures outside TA are outside the guaranteed operating temperature range of the device. Temperature measurement from –128°C to +127°C is possible using an external sensor. Temperature measurement is initiated by three methods. The first method is applicable when the part is in single-channel measurement mode. The temperature is measured 16 times and internally averaged to reduce noise. In single-channel mode, the part is continuously monitoring the selected channel, i.e., as soon as one measurement is taken another one is started on the same channel. The total time to measure a temperature channel with the ADC operating at slow speed is typically 11.4 ms (712 µs × 16) for the internal temperature sensor and 24.22 ms (1.51 ms × 16) for the external temperature sensor. The new temperature value is stored in two 8-bit registers and is ready for reading by the I2C or SPI interface. The user has the option of disabling the averaging by setting Bit 5 in the Control Configuration 2 register (Address 19h). The ADT7518 defaults on power-up with averaging enabled. Rev. A | Page 22 of 40 ADT7518 The second method is applicable when the part is in round robin measurement mode. The part measures both the internal and external temperature sensors as it cycles through all possible measurement channels. The two temperature channels are measured each time the part runs a round robin sequence. In round robin mode, the part continuously measures all channels. Temperature measurement is also initiated after every read or write to the part when the part is in either single-channel measurement mode or round robin measurement mode. Once serial communication has started, any conversion in progress is stopped and the ADC is reset. Conversion starts again immediately after the serial communication has finished. The temperature measurement proceeds normally as described in the preceding section. VDD Monitoring The ADT7518 also has the ability to monitor its own power supply. The part measures the voltage on its VDD pin to a resolution of 10 bits. The resulting value is stored in two 8-bit registers; the two LSBs are stored in register address 03h and the eight MSBs are stored in Register Address 06h. This allows the option of doing just a 1-byte read if 10-bit resolution is not important. The measured result is compared with the VHIGH and VLOW limits. If the VDD interrupt is not masked, any out-of-limit comparison generates a flag in the Interrupt Status 2 register and one or more out-of-limit results will cause the INT/INT output to pull either high or low, depending on the output polarity setting. Measuring the voltage on the VDD pin is regarded as monitoring a channel along with the internal, external, and AIN channels. The user can select the VDD channel for single-channel measurement by setting Bit C4 = 1 and setting Bits C0:C2 to all 0s in the Control Configuration 2 register. When measuring the VDD value, the reference for the ADC is sourced from the internal reference. Table 8 shows the data format. As the maximum VDD voltage measurable is 7 V, internal scaling is performed on the VDD voltage to match the 2.25 V internal reference value. Below is an example of how the transfer function works. VDD = 5 V ADC Reference = 2.25 V 1 LSB = ADC Reference/210 = 2.25/1024 = 2.226 mV Scale Factor = Full-Scale VCC/ADC Reference = 7/2.25 = 3.07 Conversion Result = VDD/(Scale Factor × LSB size) = 5/(3.07 × 2.226 mV) = 2 DCh Table 8. VDD Data Format (VREF = 2.25 V) VDD Value (V) 2.7 3 3.5 4 4.5 5 5.5 6 6.5 7 Digital Output Binary 01 1000 1011 01 1011 0111 10 0000 0000 10 0100 1001 10 1001 0010 10 1101 1100 11 0010 0101 11 0110 1110 11 1011 0111 11 1111 1111 Hex 18B 1B7 200 249 292 2DC 325 36E 3B7 3FF On-Chip Reference The ADT7518 has an on-chip 1.2 V band gap reference, which is gained up by a switched capacitor amplifier to give an output of 2.25 V. The amplifier is powered up for the duration of the device monitoring phase and is powered down once monitoring is disabled. This saves on current consumption. The internal reference is used as the reference for the ADC. The ADC is used for measuring VDD, internal temperature sensor, external temperature sensor, and AIN inputs. The internal reference is always used when measuring VDD, and the internal and external temperature sensors. The external reference is the default power-up reference for the DACs. Round Robin Measurement On power-up, the ADT7518 goes into round robin mode but monitoring is disabled. Setting Bit C0 of the Configuration Register 1 to 1 enables conversions. It sequences through all the available channels, taking a measurement from each in the following order: VDD, internal temperature sensor, external temperature sensor/(AIN1 and AIN2), AIN3, and AIN4. Pin 7 and Pin 8 can be configured to be either external temperature sensor pins or standalone analog input pins. Once conversion is completed on the AIN4 channel, the device loops around for another measurement cycle. This method of taking a measurement on all the channels in one cycle is called round robin. Setting Bit C4 of Control Configuration 2 (Address 19h) disables the round robin mode and in turn sets up the singlechannel mode. The single-channel mode is where only one channel, e.g., the internal temperature sensor, is measured in each conversion cycle. The time taken to monitor all channels will normally not be of interest, since the most recently measured value can be read at any time. For applications where the round robin time is important, typical times at 25°C are given in the specifications. Single-Channel Measurement Setting C4 of the Control Configuration 2 register enables the single-channel mode and allows the ADT7518 to focus on one channel only. A channel is selected by writing to Bits C0:C2 in the Control Configuration 2 register. For example, to select the VDD channel for monitoring, write to the Control Configuration Rev. A | Page 23 of 40 ADT7518 2 register and set C4 to 1 (if not done so already), then write all 0s to Bits C0:C2. All subsequent conversions will be done on the VDD channel only. To change the channel selection to the internal temperature channel, write to the Control Configuration 2 register and set C0 = 1. When measuring in single-channel mode, conversions on the channel selected occur directly after each other. Any communication to the ADT7518 stops the conversions, but they are restarted once the read or write operation is completed. Internal Temperature Measurement The ADT7518 contains an on-chip band gap temperature sensor whose output is digitized by the on-chip ADC. The temperature data is stored in the Internal Temperature Value register. Because both positive and negative temperatures can be measured, the temperature data is stored in twos complement format, as shown in Table 9. The thermal characteristics of the measurement sensor could change and, therefore, an offset is added to the measured value to enable the transfer function to match the thermal characteristics. This offset is added before the temperature data is stored. The offset value used is stored in the internal temperature offset register. External Temperature Measurement To prevent ground noise interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but is biased above ground by an internal diode at the D– input. As the sensor is operating in a noisy environment, C1 is provided as a noise filter. See the Layout Considerations section for more information on C1. To measure ∆VBE, the sensor is switched between operating currents of I and N × I. The resulting waveform is passed through a low-pass filter to remove noise, then to a chopper-stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage proportional to ∆VBE. This voltage is measured by the ADC to give a temperature output in 10-bit twos complement format. To further reduce the effects of noise, digital filtering is performed by averaging the results of 16 measurement cycles. Layout Considerations Digital boards can be electrically noisy environments, and care must be taken to protect the analog inputs from noise, particularly when measuring the very small voltages from a remote diode sensor. The following precautions should be taken: 1. Place the ADT7518 as close as possible to the remote sensing diode. Provided that the worst noise sources such as clock generators, data/address buses, and CRTs are avoided, this distance can be 4 inches to 8 inches. 2. Route the D+ and D– tracks close together, in parallel, with grounded guard tracks on each side. Provide a ground plane under the tracks, if possible. 3. Use wide tracks to minimize inductance and reduce noise pickup. A 10 mil track minimum width and spacing is recommended. The ADT7518 can measure the temperature of one external diode sensor or diode-connected transistor. The forward voltage of a diode or diode-connected transistor, operated at a constant current, exhibits a negative temperature coefficient of about –2 mV/°C. Unfortunately, because the absolute value of VBE varies from device to device, and individual calibration is required to null this out, the technique is unsuitable for mass production. The technique used in the ADT7518 is to measure the change in VBE when the device is operated at two different currents. This is given by ∆V BE = KT / q × 1n(N ) GND 10 MIL 10 MIL D+ 10 MIL 10 MIL where: D– K is Boltzmann’s constant. q is the charge on the carrier. T is the absolute temperature in kelvins. N is the ratio of the two currents. 10 MIL GND 10 MIL 04879-050 10 MIL Figure 50. Arrangement of Signal Tracks Figure 41 shows the input signal conditioning used to measure the output of an external temperature sensor. This figure shows the external sensor as a substrate transistor, provided for temperature monitoring on some microprocessors, but it could equally well be a discrete transistor. 4. If a discrete transistor is used, the collector is not grounded and should be linked to the base. If a PNP transistor is used, the base is connected to the D– input and the emitter to the D+ input. If an NPN transistor is used, the emitter is connected to the D– input and the base to the D+ input. A 2N3906 is recommended as the external transistor. Rev. A | Page 24 of 40 Try to minimize the number of copper/solder joints, which can cause thermocouple effects. Where copper/solder joints are used, make sure that they are in both the D+ and D– path and at the same temperature. Thermocouple effects should not be a major problem because 1°C corresponds to about 240 µV, and thermocouple voltages are about 3 µV/°C of temperature difference. Unless there are two thermocouples with a big temperature differential between them, thermocouple voltages should be much less than 200 mV. ADT7518 Interrupts Place 0.1 µF bypass and 2,200 pF input filter capacitors close to the ADT7518. 6. If the distance to the remote sensor is more than 8 inches, the use of twisted-pair cable is recommended. This will work up to about 6 feet to 12 feet. 7. For long distances (up to 100 feet), use shielded twistedpair cable, such as Belden #8451 microphone cable. Connect the twisted pair to D+ and D– and the shield to GND close to the ADT7518. Leave the remote end of the shield unconnected to avoid ground loops. Because the measurement technique uses switched current sources, excessive cable and/or filter capacitance can affect the measurement. When using long cables, the filter capacitor may be reduced or removed. Cable resistance can also introduce errors. Series resistance of 1 Ω introduces about 0.5°C error. Temperature Value Format One LSB of the ADC corresponds to 0.25°C. The ADC can theoretically measure a temperature span of 255°C. The internal temperature sensor is guaranteed to a low value limit of –40°C. It is possible to measure the full temperature span using the external temperature sensor. The temperature data format is shown in Table 9. The result of the internal or external temperature measurements is stored in the temperature value registers, and is compared with limits programmed into the internal or external high and low registers. Table 9. Temperature Data Format (Internal and External Temperature) Temperature –40°C –25°C –10°C –0.25°C 0°C +0.25°C +10°C +25°C +50°C +75°C +100°C +105°C +125°C Digital Output 11 0110 0000 11 1001 1100 11 1101 1000 11 1111 1111 00 0000 0000 00 0000 0001 00 0010 1000 00 0110 0100 00 1100 1000 01 0010 1100 01 1001 0000 01 1010 0100 01 1111 0100 The measured results from the internal temperature sensor, external temperature sensor, VDD pin, and AIN inputs are compared with the THIGH/VHIGH (greater than comparison) and TLOW/VLOW (less than or equal to comparison) limits. An interrupt occurs if the measurement exceeds or equals the limit registers. These limits are stored in on-chip registers. Note that the limit registers are 8 bits long while the conversion results are 10 bits long. If the limits are not masked, any out-of-limit comparisons generate flags that are stored in the Interrupt Status 1 register (Address 00h) and Interrupt Status 2 register (Address 01h). One or more out-of-limit results will cause the INT/INT output to pull either high or low depending on the output polarity setting. It is good design practice to mask out interrupts for channels that are of no concern to the application. Figure 49 shows the interrupt structure for the ADT7518. It gives a block diagram representation of how the various measurement channels affect the INT/INT pin. ADT7518 REGISTERS The ADT7518 contains registers that are used to store the results of external and internal temperature measurements, VDD value measurements, analog input measurements, high and low temperature limits, supply voltage and analog input limits, to set output DAC voltage levels, to configure multipurpose pins, and generally to control the device. A description of these registers follows. The register map is divided into registers of 8 bits. Each register has its own individual address, but some consist of data that is linked to other registers. These registers hold the 10-bit conversion results of measurements taken on the temperature, VDD, and AIN channels. For example, the eight MSBs of the VDD measurement are stored in Register Address 06h, while the two LSBs are stored in Register Address 03h. These types of registers are linked such that when the LSB register is read first, the MSB registers associated with that LSB register are locked to prevent any updates. To unlock these MSB registers, the user has only to read any one of them, which will have the effect of unlocking all previously locked MSB registers. So, for the preceding example, if Register 03h was read first, MSB Registers 06h and 07h would be locked to prevent any updates to them. If Register 06h were read, this register and Register 07h would be subsequently unlocked. FIRST READ COMMAND Temperature Conversion Formula: Positive Temperature = ADC Code/4 Negative Temperature = (ADC Code* – 512)/4 *where DB9 is removed from the ADC code. LSB REGISTER OUTPUT DATA LOCK ASSOCIATED MSB REGISTERS Figure 51. Phase 1 of 10-Bit Read Rev. A | Page 25 of 40 04879-051 5. ADT7518 MSB REGISTER OUTPUT DATA UNLOCK ASSOCIATED MSB REGISTERS 04879-052 SECOND READ COMMAND RD/WR Address 2Fh 30h 31h–4Ch 4Dh Name AIN4 VHIGH Limit AIN4 VLOW Limit Reserved Device ID 4Eh 4Fh 50h–7Eh 7Fh 80h–FFh Manufacturer’s ID Silicon Revision Reserved SPI Lock Status Reserved Power-On Default FFh 00h 03h/0Bh/ 07h 41h 04h 00h 00h 00h Figure 52. Phase 2 of 10-Bit Read If an MSB register is read first, its corresponding LSB register is not locked, leaving the user with the option of just reading back 8 bits (MSB) of a 10-bit conversion result. Reading an MSB register first does not lock other MSB registers, and likewise reading an LSB register first does not lock other LSB registers. Table 10. ADT7518 Registers RD/WR Address 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch–10h 11h 12h 13h 14h 15h 16h 17h 18h 19h 1Ah 1Bh 1Ch 1Dh 1Eh 1Fh 20h 21h 22h 23h 24h 25h 26h 27h 28h 29h–2Ah 2Bh 2Bh 2Ch 2Dh 2Eh Name Interrupt Status 1 Interrupt Status 2 Reserved Internal Temp and VDD LSBs External Temp and AIN1 to AIN4 LSBs Reserved VDD MSBs Internal Temp MSBs External Temp MSBs/AIN1 MSBs AIN2 MSBs AIN3 MSBs AIN4 MSBs Reserved DAC A MSBs Reserved DAC B MSBs Reserved DAC C MSBs Reserved DAC D MSBs Control Configuration 1 Control Configuration 2 Control Configuration 3 DAC Configuration LDAC Configuration Interrupt Mask 1 Interrupt Mask 2 Internal Temp Offset External Temp Offset Internal Analog Temp Offset External Analog Temp Offset VDD VHIGH Limit VDD VLOW Limit Internal THIGH Limit Internal TLOW Limit External THIGH/AIN1 VHIGH Limits External TLOW/AIN1 VLOW Limits Reserved AIN2 VHIGH Limit AIN2 VHIGH Limit AIN2 VLOW Limit AIN3 VHIGH Limit AIN3 VLOW Limit Power-On Default 00h 00h Interrupt Status 1 Register (Read-Only) [Address = 00h] This 8-bit read-only register reflects the status of some of the interrupts that can cause the INT/INT pin to go active. This register is reset by a read operation, provided that any out-oflimit event has been corrected. It is also reset by a software reset. Table 11. Interrupt Status 1 Register 00h 00h 00h xxh 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h D8h D8h C7h 62h 64h C9h FFh 00h D7 0* FFh FFh 00h FFh 00h This 8-bit read-only register reflects the status of the VDD interrupt that can cause the INT/INT pin to go active. This register is reset by a read operation, provided that any out-of-limit event has been corrected. It is also reset by a software reset. D6 0* D5 0* D4 0* D3 0* D2 0* D1 0* D0 0* *Default settings at power-up Table 12. Bit D0 D1 D2 D3 D4 D5 D6 D7 Function 1 when the internal temperature value exceeds THIGH limit. Any internal temperature reading greater than the set limit will cause an out-of-limit event. 1 when internal temperature value exceeds TLOW limit. Any internal temperature reading less than or equal to the set limit will cause an out-of-limit event. This status bit is linked to the configuration of Pins 7 and 8. If configured for the external temperature sensor, this bit is 1 when the external temperature value the exceeds THIGH limit. The default value for this limit register is –1°C, so any external temperature reading greater than the set limit will cause an out-of-limit event. If configured for AIN1 and AIN2, this bit is 1 when AIN1 input voltage exceeds VHIGH or VLOW limits. 1 when external temperature value exceeds TLOW limit. The default value for this limit register is 0°C, so any external temperature reading less than or equal to the set limit will cause an out-of-limit event. 1 Indicates a fault (open or short) for the external temperature sensor. 1 when AIN2 voltage is greater than its corresponding VHIGH limit. 1 when AIN2 voltage is less than or equal to its corresponding VLOW limit. 1 when AIN3 voltage is greater than its corresponding VHIGH limit. 1 when AIN3 voltage is less than or equal to its corresponding VLOW limit. 1 when AIN4 voltage is greater than its corresponding VHIGH limit. 1 when AIN4 voltage is less than or equal to its corresponding VLOW limit. Interrupt Status 2 Register (Read-Only) [Address = 01h] Rev. A | Page 26 of 40 ADT7518 VDD Value Register MSBs (Read-Only) [Address = 6h] Table 13. Interrupt Status 2 Register D7 N/A D6 N/A D5 N/A D4 0* D3 N/A D2 N/A D1 N/A D0 N/A This 8-bit read-only register stores the supply voltage value. The eight MSBs of the 10-bit value are stored in this register. *Default settings at power-up. Table 19. VDD Value MSBs Table 14. D7 V9 x* Bit D4 Function 1 when VDD value is greater than its corresponding VHIGH limit. 1 when VDD is less than or equal to its corresponding VLOW limit. Internal Temperature Value/VDD Value Register LSBs (ReadOnly) [Address = 03h] D6 V8 x* D5 V7 x* D4 V6 x* D3 V5 x* D2 V4 x* D1 V3 x* D0 V2 x* *Loaded with VDD value after power-up. Internal Temperature Value Register MSBs (Read-Only) [Address = 07h] This 8-bit read-only register stores the two LSBs of the 10-bit temperature reading from the internal temperature sensor and the two LSBs of the 10-bit supply voltage reading. This 8-bit read-only register stores the internal temperature value from the internal temperature sensor in twos complement format. The eight MSBs of the 10-bit value are stored in this register. Table 15. Internal Temperature/VDD LSBs Table 20. Internal Temperature Value MSBs D7 N/A N/A D6 N/A N/A D5 N/A N/A D4 N/A N/A D3 V1 0* D2 LSB 0* D1 T1 0* D0 LSB 0* D7 T9 0* D6 T8 0* D5 T7 0* D4 T6 0* D3 T5 0* D2 T4 0* D1 T3 0* D0 T2 0* *Default settings at power-up *Default settings at power-up Table 16. External Temperature Value or Analog Input AIN1 Register MSBs (Read-Only) [Address = 08h] Bit D0 D1 D2 D3 Function LSB of Internal Temperature Value B1 of Internal Temperature Value LSB of VDD Value B1 of VDD Value This 8-bit read-only register stores, if selected, the external temperature value or the analog input AIN1 value. Selection is done in the Control Configuration 1 register. The external temperature value is stored in twos complement format. The eight MSBs of the 10-bit value are stored in this register. External Temperature Value and Analog Inputs 1 to 4 Register LSBs (Read-Only) [Address = 04h] Table 21. External Temperature Value/Analog Inputs MSBs This is an 8-bit read-only register. Bits D2:D7 store the two LSBs of the analog inputs AIN2 to AIN4. Bits D0:D1 store the two LSBs of either the external temperature value or AIN1 input value. The type of input for D0 and D1 is selected by Bits C1:C2 of the Control Configuration Register 1. Table 17. External Temperature and AIN1 to AIN4 LSBs D7 A4 0* D6 A4LSB 0* D5 A3 0* D4 A3LSB 0* D3 A2 0* D2 A2LSB 0* D1 T/A 0* *Default settings at power-up Table 18. Bit D0 D1 D2 D3 D4 D5 D6 D7 Function LSB of External Temperature Value or AIN1 Value Bit 1 of External Temperature Value or AIN1 Value LSB of AIN2 Value Bit 1 of AIN2 Value LSB of AIN3 Value Bit 1 of AIN3 Value LSB of AIN4 Value Bit 1 of AIN4 Value D0 T/ALSB 0* D7 T/A9 0* D6 T/A8 0* D5 T/A7 0* D4 T/A6 0* D3 T/A5 0* D2 T/A4 0* D1 T/A3 0* D0 T/A2 0* *Default settings at power-up AIN2 Register MSBs (Read) [Address = 09h] This 8-bit read register contains the eight MSBs of the AIN2 analog input voltage word. The value in this register is combined with Bits D2:3 of the external temperature value and Analog Inputs 1 to 4 register LSBs, Address 04h, to give the full 10-bit conversion result of the analog value on the AIN2 pin. Table 22. AIN2 MSBs D7 MSB 0* D6 A8 0* D5 A7 0* D4 A6 0* D3 A5 0* D2 A4 0* D1 A3 0* D0 A2 0* *Default settings at power-up AIN3 Register MSBs (Read) [Address = 0Ah] This 8-bit read register contains the eight MSBs of the AIN3 analog input voltage word. The value in this register is combined with Bits D4:5 of the external temperature value and Analog Inputs 1 to 4 register LSBs, Address 04h, to give the full 10-bit conversion result of the analog value on the AIN3 pin. Rev. A | Page 27 of 40 ADT7518 Table 23. AIN3 MSBs D7 MSB 0* D6 A8 0* D5 A7 0* Table 26. DAC B D4 A6 0* D3 A5 0* D2 A4 0* D1 A3 0* D0 A2 0* D7 MSB 0* D6 B8 0* D5 B7 0* D4 B6 0* D3 B5 0* D2 B4 0* D1 B3 0* D0 B2 0* *Default settings at power-up *Default settings at power-up AIN4 Register MSBs (Read) [Address = 0Bh] DAC C Register (Read/Write) [Address = 15h] This 8-bit read register contains the eight MSBs of the AIN4 analog input voltage word. The value in this register is combined with Bits D6:7 of the external temperature value and Analog Inputs 1 to 4 register LSBs, Address 04h, to give the full 10-bit conversion result of the analog value on the AIN4 pin. This 8-bit read/write register contains the eight bits of the DAC C word. The value in this register is converted to an analog voltage on the VOUT-C pin. On power-up, the voltage output on the VOUT-C pin is 0 V. Table 24. AIN4 MSBs D7 MSB 0* D7 MSB 0* D6 A8 0* D5 A7 0* D4 A6 0* D3 A5 0* D2 A4 0* D1 A3 0* D0 A2 0* *Default settings at power-up This 8-bit read/write register contains the eight bits of the DAC A word. The value in this register is converted to an analog voltage on the VOUT-A pin. On power-up, the voltage output on the VOUT-A pin is 0 V. Table 25. DAC A D6 B8 0* D5 B7 0* D6 B8 0* D5 B7 0* D4 B6 0* D3 B5 0* D2 B4 0* D1 B3 0* D0 B2 0* *Default settings at power-up DAC D Register (Read/Write) [Address = 17h] DAC A Register (Read/Write) [Address = 11h] D7 MSB 0* Table 27. DAC C D4 B6 0* D3 B5 0* D2 B4 0* D1 B3 0* D0 B2 0* *Default settings at power-up This 8-bit read/write register contains the eight bits of the DAC D word. The value in this register is converted to an analog voltage on the VOUT-D pin. On power-up, the voltage output on the VOUT-D pin is 0 V. Table 28. DAC D D7 MSB 0* D6 B8 0* D5 B7 0* D4 B6 0* D3 B5 0* D2 B4 0* D1 B3 0* D0 B2 0* *Default settings at power-up Control Configuration 1 Register (Read/Write) [Address = 18h] DAC B Register (Read/Write) [Address = 13h] This 8-bit read/write register contains the eight bits of the DAC B word. The value in this register is converted to an analog voltage on the VOUT-B pin. On power-up, the voltage output on the VOUT-B pin is 0 V. This configuration register is an 8-bit read/write register that is used to set up some of the operating modes of the ADT7518. Table 29. Control Configuration 1 D7 PD 0* D6 C6 0* D5 C5 0* *Default settings at power-up Rev. A | Page 28 of 40 D4 C4 0* D3 C3 0* D2 C2 0* D1 C1 0* D0 C0 0* ADT7518 Table 30. Bit C0 C2:C1 C3 C4 C5 C6 PD Bit Function This bit enables/disables conversions in round robin and single-channel mode. ADT7518 powers up in round robin mode but monitoring is not initiated until this bit is set. The default = 0. 0 = Stop monitoring. 1 = Start monitoring. Selects between the two different analog inputs on Pins 7 and 8. ADT7518 powers up with AIN1 and AIN2 selected. 00 = AIN1 and AIN2 selected. 01 = Undefined. 10 = External TDM selected. 11 = Undefined. Selects between digital (LDAC) and analog inputs (AIN3) on Pin 9. When AIN3 is selected, Bit C3 of the Control Configuration 3 register is masked and has no effect until LDAC is selected as the input on Pin 9. 0 = LDAC selected. 1 = AIN3 selected. Reserved. Write 0 only. 0 = Enable INT/INT output. 1 = Disable INT/INT output. Configures INT/INT output polarity. 0 = Active low. 1 = Active high. Power-Down Bit. Setting this bit to 1 puts the ADT7518 into standby mode. In this mode, both ADC and DACs are fully powered down, but the serial interface is still operational. To power up the part again, just write 0 to this bit. C3 C4 C5 C6 C7 Function 101 = AIN4. 110–111 = Reserved. Reserved. Selects between single-channel and round robin conversion cycle. The default is round robin. 0 = Round robin. 1 = Single channel. Default condition is to average every measurement on all channels 16 times. This bit disables this averaging. Channels affected are temperature, analog inputs, and VDD. 0 = Enable averaging. 1 = Disable averaging. SMBus timeout on the serial clock puts a 25 ms limit on the pulse width of the clock, ensuring that a fault on the master SCL does not lock up the SDA line. 0 = Disable SMBus timeout. 1 = Enable SMBus timeout. Software Reset. Setting this bit to 1 causes a software reset. All registers and DAC outputs will reset to their default settings. Control Configuration 3 Register (Read/Write) [Address = 1Ah] This configuration register is an 8-bit read/write register that is used to set up some of the operating modes of the ADT7518. Table 33. Control Configuration 3 D7 C7 0* D6 C6 0* D5 C5 0* Control Configuration 2 Register (Read/Write) [Address = 19h] *Default settings at power-up This configuration register is an 8-bit read/write register that is used to set up some of the operating modes of the ADT7518. Bit C0 D6 C6 0* D5 C5 0* D4 C4 0* D3 C3 0* D2 C2 0* D1 C1 0* D0 C0 0* C2:1 C3 * Default settings at power-up Table 32. Bit C2:0 D3 C3 0* D2 C2 0* D1 C1 0* D0 C0 0* Table 34. Table 31. Control Configuration 2 D7 C7 0* D4 C4 0* C4 Function In single-channel mode, these bits select between VDD, the internal temperature sensor, external temperature sensor/AIN1, AIN2, AIN3, and AIN4 for conversion. The default is VDD. 000 = VDD. 001 = Internal temperature sensor. 010 = External temperature sensor/AIN1. (Bits C1:C2 of the Control Configuration 1 register affect this selection). 011 = AIN2. 100 = AIN3. C5 C6 C7 Rev. A | Page 29 of 40 Function Selects between fast and slow ADC conversion speeds. 0 = ADC clock at 1.4 kHz. 1 = ADC clock at 22.5 kHz. D+ and D– analog filters are disabled. Reserved. Write 0 only. 0 = LDAC pin controls updating of DAC outputs. 1 = DAC configuration register and LDAC configuration register control updating of DAC outputs. Selects the ADC reference to be either internal VREF or VDD for analog inputs. 0 = Internal VREF. 1 = VDD. Setting this bit selects DAC A voltage output to be proportional to the internal temperature measurement. Setting this bit selects DAC B voltage output to be proportional to the external temperature measurement. Reserved. Write 0 only. ADT7518 DAC Configuration Register (Read/Write) [Address = 1Bh] Table 38. This configuration register is an 8-bit read/write register that is used to control the output ranges of all four DACs and also to control the loading of the DAC registers if the LDAC pin is disabled (Bit C3 = 1, Control Configuration 3 register). Table 35. DAC Configuration D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* Bit D0 D1 D2 D3 D4 * Default settings at power-up Table 36. Bit D0 D1 D2 D3 D5:D4 D6:D7 Function Selects the output range of DAC A. 0 = 0 V to VREF. 1 = 0 V to 2VREF. Selects the output range of DAC B. 0 = 0 V to VREF. 1 = 0 V to 2VREF. Selects the output range of DAC C. 0 = 0 V to VREF. 1 = 0 V to 2VREF. Selects the output range of DAC D. 0 = 0 V to VREF. 1 = 0 V to 2VREF. 00 = A write to any DAC register generates LDAC command that updates that DAC only. 01 = A write to DAC B or DAC D register generates LDAC command that updates DACs A, B or DACs C, D, respectively. 10 = A write to DAC D register generates LDAC command that updates all four DACs. 11 = LDAC command generated from LDAC register. Reserved. Write 0s only. LDAC Configuration Register (Write-Only) [Address = 1Ch] D5 D6:D7 Interrupt Mask 1 Register (Read/Write) [Address = 1Dh] This mask register is an 8-bit read/write register that can be used to mask any interrupts that can cause the INT/INT pin to go active. Table 39. Interrupt Mask 1 D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* Table 40. Bit D0 D1 D3 D4 D5 D6 Table 37. LDAC Configuration D7 D7 0* D6 D6 0* * Default settings at power-up D2 This configuration register is an 8-bit write register that is used to control the updating of the quad DAC outputs if the LDAC pin is disabled and Bits D4:D5 of the DAC configuration register are both set to 1. Also selects either the internal or external VREF for all four DACs. Bits D0:D3 in this register are self-clearing, i.e., reading back from this register will always give 0s for these bits. Function Writing a 1 to this bit will generate the LDAC command to update DAC A output only. Writing a 1 to this bit will generate the LDAC command to update DAC B output only. Writing a 1 to this bit will generate the LDAC command to update DAC C output only. Writing a 1 to this bit will generate the LDAC command to update DAC D output only. Selects either internal VREF or external VREF for DACs A and B. 0 = External VREF 1 = Internal VREF. Selects either internal VREF or external VREF for DACs C and D. 0 = External VREF 1 = Internal VREF Reserved. Write 0s only. D7 * Default settings at power-up Rev. A | Page 30 of 40 Function 0 = Enable internal THIGH interrupt. 1 = Disable internal THIGH interrupt. 0 = Enable internal TLOW interrupt. 1 = Disable internal TLOW interrupt. 0 = Enable external THIGH interrupt or AIN1 interrupt. 1 = Disable external THIGH interrupt or AIN1 interrupt. 0 = Enable external TLOW interrupt. 1 = Disable external TLOW interrupt. 0 = Enable external temperature fault interrupt.. 1 = Disable external temperature fault interrupt. 0 = Enable AIN2 interrupt. 1 = Disable AIN2 interrupt. 0 = Enable AIN3 interrupt. 1 = Disable AIN3 interrupt. 0 = Enable AIN4 interrupt. 1 = Disable AIN4 interrupt. D0 D0 0* ADT7518 Interrupt Mask 2 Register (Read/Write) [Address = 1Eh] This mask register is an 8-bit read/write register that can be used to mask any interrupts that can cause the INT/INT pin to go active. Table 41. Interrupt Mask 2 D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up Table 42. Bit D0:D3 D4 Function Reserved. Write 0s only. 0 = Enable VDD interrupts. 1 = Disable VDD interrupts. Reserved. Write 0s only. D5:D7 D7 D7 1* Table 43. Internal Temperature Offset D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up This register contains the offset value for the external temperature channel. A twos complement number can be written to this register, which is then added to the measured result before it is stored or compared to limits. In this way, a one-point calibration can be done whereby the whole transfer function of the channel can be moved up or down. From a software point of view, this may be a very simple method to vary the characteristics of the measurement channel if the thermal characteristics change. Because it is an 8-bit register, the temperature resolution is 1°C. Table 44. External Temperature Offset D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D5 D5 0* D4 D4 1* D3 D3 1* D2 D2 0* D1 D1 0* D0 D0 0* External Analog Temperature Offset Register (Read/Write) [Address = 22h] This register contains the offset value for the external thermal voltage output. A twos complement number can be written to this register which is then added to the measured result before it is converted by DAC B. Varying the value in this register has the effect of varying the temperature span. For example, the output voltage can represent a temperature span of –128°C to +127°C or even 0°C to +127°C. In essence, this register changes the position of 0 V on the temperature scale. Temperatures other than –128°C to +127°C will produce an upper deadband on the DAC B output. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is –40°C. Table 46. External Analog Temperature Offset D7 D7 1* External Temperature Offset Register (Read/Write) [Address = 20h] D7 D7 0* D6 D6 1* * Default settings at power-up This register contains the offset value for the internal temperature channel. A twos complement number can be written to this register which is then added to the measured result before it is stored or compared to limits. In this way, a one-point calibration can be done whereby the whole transfer function of the channel can be moved up or down. From a software point of view, this may be a very simple method to vary the characteristics of the measurement channel if the thermal characteristics change. Because it is an 8-bit register, the temperature resolution is 1°C. D6 D6 0* This register contains the offset value for the internal thermal voltage output. A twos complement number can be written to this register, which is then added to the measured result before it is converted by DAC A. Varying the value in this register has the effect of varying the temperature span. For example, the output voltage can represent a temperature span of –128°C to +127°C or even 0°C to +127°C. In essence, this register changes the position of 0 V on the temperature scale. Temperatures other than –128°C to +127°C will produce an upper deadband on the DAC A output. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is –40°C. Table 45. Internal Analog Temperature Offset Internal Temperature Offset Register (Read/Write) [Address = 1Fh] D7 D7 0* Internal Analog Temperature Offset Register (Read/Write) [Address = 21h] D0 D0 0* D6 D6 1* D5 D5 0* D4 D4 1* D3 D3 1* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up VDD VHIGH Limit Register (Read/Write) [Address = 23h] This limit register is an 8-bit read/write register that stores the VDD upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured VDD value has to be greater than the value in this register. The default value is 5.46 V. Table 47. VDD VHIGH Limit D7 D7 1* D6 D6 1* D5 D5 0* * Default settings at power-up * Default settings at power-up Rev. A | Page 31 of 40 D4 D4 0* D3 D3 0* D2 D2 1* D1 D1 1* D0 D0 1* ADT7518 VDD VLOW Limit Register (Read/Write) [Address = 24h] This limit register is an 8-bit read/write register that stores the VDD lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured VDD value has to be less than or equal to the value in this register. The default value is 2.7 V. Table 48. VDD VLOW Limit D7 D7 0* D6 D6 1* D5 D5 1* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 1* D0 D0 0* * Default settings at power-up Internal THIGH Limit Register (Read/Write) [Address = 25h] This limit register is an 8-bit read/write register that stores the twos complement of the internal temperature upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured internal temperature value has to be greater than the value in this register. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is +100°C. Table 49. Internal THIGH Limit D7 D7 0* D6 D6 1* D5 D5 1* D4 D4 0* D3 D3 0* D2 D2 1* D1 D1 0* D0 D0 0* * Default settings at power-up Internal TLOW Limit Register (Read/Write) [Address = 26h] This limit register is an 8-bit read/write register that stores the twos complement of the internal temperature lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured internal temperature value has to be more negative than or equal to the value in this register. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is –55°C. D6 D6 1* D5 D5 0* D4 D4 0* Table 51. AIN1 VHIGH Limit D7 D7 1* D6 D6 1* D5 D5 1* D4 D4 1* D3 D3 1* D2 D2 1* D1 D1 1* D0 D0 1* * Default settings at power-up External TLOW/AIN1 VLOW Limit Register (Read/Write) [Address = 28h] If Pins 7 and 8 are configured for the external temperature sensor, this limit register is an 8-bit read/write register that stores the twos complement of the external temperature lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured external temperature value has to be more negative than or equal to the value in this register. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is 0°C. If Pins 7 and 8 are configured for AIN1 and AIN2 inputs, this limit register is an 8-bit read/write register that stores the AIN1 input lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN1 value has to be less than or equal to the value in this register. As it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. Because the power-up default settings for Pins 7 and 8 are AIN1 and AIN2 inputs, the default value for this limit register is 0 V. Table 52. AIN1 VLOW Limit Table 50. Internal TLOW Limit D7 D7 1* input upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN1 value has to be greater than the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. Because the power-up default settings for Pins 7 and 8 are AIN1 and AIN2 inputs, the default value for this limit register is full-scale voltage. D3 D3 1* D2 D2 0* D1 D1 0* D0 D0 1* * Default settings at power-up D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up AIN2 VHIGH Limit Register (Read/Write) [Address = 2Bh] External THIGH/AIN1 VHIGH Limit Register (Read/Write) [Address = 27h] If Pins 7 and 8 are configured for the external temperature sensor, this limit register is an 8-bit read/write register that stores the twos complement of the external temperature upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured external temperature value has to be greater than the value in this register. Because it is an 8-bit register, the temperature resolution is 1°C. The default value is –1°C. If Pins 7 and 8 are configured for AIN1 and AIN2 inputs, this limit register is an 8-bit read/write register that stores the AIN1 This limit register is an 8-bit read/write register that stores the AIN2 input upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN2 value has to be greater than the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is full-scale voltage. Table 53. AIN2 VHIGH Limit D7 D7 1* D6 D6 1* D5 D5 1* * Default settings at power-up Rev. A | Page 32 of 40 D4 D4 1* D3 D3 1* D2 D2 1* D1 D1 1* D0 D0 1* ADT7518 AIN2 VLOW Limit Register (Read/Write) [Address = 2Ch] Table 57. AIN4 VHIGH Limit This limit register is an 8-bit read/write register that stores the AIN2 input lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN2 value has to be less than or equal to the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is 0 V. D7 D7 1* Table 54. AIN2 VLOW Limit D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up This limit register is an 8-bit read/write register that stores the AIN3 input upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN3 value has to be greater than the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is full-scale voltage. D5 D5 1* D4 D4 1* D3 D3 1* D2 D2 1* D1 D1 1* D0 D0 1* * Default settings at power-up AIN3 VLOW Limit Register (Read/Write) [Address = 2Eh] This limit register is an 8-bit read/write register that stores the AIN3 input lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN3 value has to be less than or equal to the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is 0 V. Table 56. AIN3 VLOW Limit D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 1* D3 D3 1* D2 D2 1* D1 D1 1* D0 D0 1* * Default settings at power-up AIN4 VLOW Limit Register (Read/Write) [Address = 30h] This limit register is an 8-bit read/write register that stores the AIN4 input lower limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN4 value has to be less than or equal to the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is 0 V. D4 D4 0* D7 D7 0* D6 D6 0* D5 D5 0* D4 D4 0* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up Device ID Register (Read-Only) [Address = 4Dh] This 8-bit read-only register contains a device identifier byte: ADT7518 = 0Bh. Manufacturer’s ID Register (Read-Only) [Address = 4Eh] This register contains the manufacturer’s identification number. ADI’s ID number is 41h. Table 55. AIN3 VHIGH Limit D6 D6 1* D5 D5 1* Table 58. AIN4 VLOW Limit AIN3 VHIGH Limit Register (Read/Write) [Address = 2Dh] D7 D7 1* D6 D6 1* D3 D3 0* D2 D2 0* D1 D1 0* D0 D0 0* * Default settings at power-up AIN4 VHIGH Limit Register (Read/Write) [Address = 2Fh] This limit register is an 8-bit read/write register that stores the AIN4 input upper limit, which will cause an interrupt and activate the INT/INT output (if enabled). For this to happen, the measured AIN4 value has to be greater than the value in this register. Because it is an 8-bit register, the resolution is four times less than the resolution of the 10-bit ADC. The default value is full-scale voltage. Silicon Revision Register (Read-Only) [Address = 4Fh] This register is divided into four LSBs representing the stepping and the four MSBs representing the version. The stepping contains the manufacturer’s code for minor revisions or steppings to the silicon. The version is the ADT7518 version number. SPI Lock Status Register (Read-Only) [Address = 7Fh] Bit D0 (LSB) of this read-only register indicates whether or not the SPI interface is locked. Writing to this register will cause the device to malfunction. The default value is 00h. 0 = I2C interface. 1 = SPI interface selected and locked. SERIAL INTERFACE There are two serial interfaces that can be used on this part: I2C and SPI. The device will power up with the serial interface in I2C mode, but it is not locked into this mode. To stay in I2C mode, it is recommended that the user tie the CS line to either VCC or GND. It is not possible to lock the I2C mode, but it is possible to select and lock the SPI mode. Rev. A | Page 33 of 40 ADT7518 A CS (START HIGH) B C SPI FRAMING EDGE SPI LOCKED ON THIRD RISING EDGE A B C 04879-055 CS (START LOW) SPI FRAMING EDGE SPI LOCKED ON THIRD RISING EDGE Figure 53. Serial Interface—Selecting and Locking SPI Protocol To select and lock the interface into the SPI mode, a number of pulses must be sent down the CS line (Pin 4). The following section describes how this is done. ADT7518 LOCK AND SELECT SPI CS Once the SPI communication protocol has been locked in, it cannot be unlocked while the device is still powered up. Bit D0 of the SPI lock status register (Address 7Fh) is set to 1 when a successful SPI interface lock has been accomplished. To reset the serial interface, the user must power down the part and power it up again. A software reset does not reset the serial interface. VDD 820 Ω 820 Ω 820 Ω SPI FRAMING EDGE DIN 04879-054 SCLK DOUT Figure 55. Typical SPI Interface Connection 2 Serial Interface Selection I C Serial Interface The CS line controls the selection between I2C and SPI. Figure 53 shows the selection process necessary to lock the SPI interface mode. Like all I2C-compatible devices, the ADT7518 has a 7-bit serial address. The four MSBs of this address for the ADT7518 are set to 1001. The three LSBs are set by Pin 11, ADD. The ADD pin can be configured three ways to give three different address options: low, floating, and high. Setting the ADD pin low gives a serial bus address of 1001 000, leaving it floating gives the address 1001 010, and setting it high gives the address 1001 011. The recommended pull-up resistor value is 10 kΩ. To communicate to the ADT7518 using the SPI protocol, send three pulses down the CS line as shown in Figure 53. On the third rising edge (marked as C in Figure 53), the part selects and locks the SPI interface. The user is now limited to communicating to the device using the SPI protocol. As per most SPI standards, the CS line must be low during every SPI communication to the ADT7518 and high all other times. Typical examples of how to connect the dual interface as I2C or SPI is shown in Figure 54 and Figure 55. The following sections describe in detail how to use the I2C and SPI protocols associated with the ADT7518. ADT7518 VDD VDD 10kΩ 10kΩ CS The ADT7518 supports SMBus packet error checking (PEC), but its use is optional. It is triggered by supplying the extra clocks for the PEC byte. The PEC is calculated using CRC-8. The frame clock sequence (FCS) conforms to CRC-8 by the polynominal C( x ) = x 8 + x 2 + x 1 + 1 SDA I2C ADDRESS = 1001 000 04879-053 SCL ADD There is an enable/disable bit for the SMBus timeout. When this is enabled, the SMBus will time out after 25 ms of no activity. To enable it, set Bit 6 of the Control Configuration 2 register. The power-on default is with the SMBus timeout disabled. Consult the SMBus specification (www.smbus.org) for more information. Figure 54. Typical I2C Interface Connection Rev. A | Page 34 of 40 ADT7518 The serial bus protocol operates as follows: Writing to the Address Pointer Register for a Subsequent Read 1. The master initiates a data transfer by establishing a start condition, defined as a high to low transition on the serial data line SDA while the serial clock line SCL remains high. This indicates that an address/data stream will follow. All slave peripherals connected to the serial bus respond to the start condition and shift in the next eight bits, consisting of a 7-bit address (MSB first) plus an R/W bit, which determines the direction of the data transfer, i.e., whether data will be written to or read from the slave device. To read data from a particular register, the address pointer register must contain the address of that register. If it does not, the correct address must be written to the address pointer register by performing a single-byte write operation, as shown in Figure 56. The write operation consists of the serial bus address followed by the address pointer byte. No data is written to any of the data registers. A read operation is then performed to read the register. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the acknowledge bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is 0 the master will write to the slave device. If the R/W bit is 1, the master will read from the slave device. All registers are 8-bit registers, so only one byte of data can be written to each register. Writing a single byte of data to one of these read/write registers consists of the serial bus address, the data register address written to the address pointer register, followed by the data byte written to the selected data register. This is illustrated in Figure 57. To write to a different register, another start or repeated start is required. If more than one byte of data is sent in one communication operation, the addressed register will repeatedly load until the last data byte is sent. Data is sent over the serial bus in sequences of nine clock pulses: eight bits of data followed by an acknowledge bit from the receiver of data. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, since a low to high transition when the clock is high may be interpreted as a stop signal. Reading Data from the ADT7518 2. 3. When all data bytes have been read or written, stop conditions are established. In write mode, the master will pull the data line high during the 10th clock pulse to assert a stop condition. In read mode, the master device will pull the data line high during the low period before the ninth clock pulse. This is known as No Acknowledge. The master will then take the data line low during the low period before the 10th clock pulse, and then high during the 10th clock pulse to assert a stop condition. Any number of bytes of data can be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. The I2C address set up by the ADD pin is not latched by the device until after this address has been sent twice. On the eighth SCL cycle of the second valid communication, the serial bus address is latched in. This is the SCL cycle directly after the device has seen its own I2C serial bus address. Any subsequent changes on this pin will have no effect on the I2C serial bus address. Writing to the ADT7518 Depending on the register being written to, there are two different writes for the ADT7518. It is not possible to do a block write to this part, i.e., no I2C autoincrement. Writing Data to a Register Reading data from the ADT7518 is done in a 1-byte operation. Reading back the contents of a register is shown in Figure 58. The register address had previously been set up by a single-byte write operation to the address pointer register. To read from another register, write to the address pointer register again to set up the relevant register address. Thus, block reads are not possible, i.e., no I2C autoincrement. SPI Serial Interface The SPI serial interface of the ADT7518 consists of four wires: CS, SCLK, DIN, and DOUT. The CS line is used to select the device when more than one device is connected to the serial clock and data lines. The CS line is also used to distinguish between any two separate serial communications (see Figure 63 for a graphical explanation). The SCLK line is used to clock data in and out of the part. The DIN line is used to write to the registers, and the DOUT line is used to read data back from the registers. The recommended pull-up resistor value is between 500 Ω and 820 Ω. The part operates in slave mode and requires an externally applied serial clock to the SCLK input. The serial interface is designed to allow the part to be interfaced to systems that provide a serial clock that is synchronized to the serial data. There are two types of serial operations, read and write. Command words are used to distinguish read operations from write operations. These command words are given in Table 59. Address autoincrement is possible in SPI mode. Table 59. SPI Command Words Write 90h (1001 0000) Rev. A | Page 35 of 40 Read 91h (1001 0001) ADT7518 1 9 1 9 SCL 0 1 A2 A1 A0 P7 R/W START BY MASTER P6 P5 P4 P3 P2 P1 P0 ACK. BY ADT7518 ACK. BY ADT7518 FRAME 1 SERIAL BUS ADDRESS BYTE STOP BY MASTER 04879-056 0 1 SDA FRAME 2 ADDRESS POINTER REGISTER BYTE Figure 56. I2C—Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation 1 9 1 9 SCL SDA 1 0 0 1 A2 A1 A0 P7 R/W START BY MASTER P6 P5 P4 P3 P2 P1 P0 ACK. BY ADT7518 ACK. BY ADT7518 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE 1 9 SCL (CONTINUED) SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 04879-057 ACK. BY STOP BY ADT7518 MASTER FRAME 3 DATA BYTE Figure 57. I2C—Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register 1 9 1 9 SCL 1 0 0 1 A2 A1 A0 R/W D7 D6 D5 D4 D3 D2 D1 ACK. BY ADT7518 START BY MASTER FRAME 1 SERIAL BUS ADDRESS BYTE D0 NO ACK. BY MASTER FRAME 2 SINGLE DATA BYTE FROM ADT7518 STOP BY MASTER 04879-058 SDA Figure 58. I2C—Reading a Single Byte of Data from a Selected Register Write Operation Read Operation Figure 59 shows the timing diagram for a write operation to the ADT7518. Data is clocked into the registers on the rising edge of SCLK. When the CS line is high, the DIN and DOUT lines are in three-state mode. Only when the CS goes from a high to a low does the part accept any data on the DIN line. In SPI mode, the address pointer register is capable of autoincrementing to the next register in the register map without having to load the address pointer register each time. In Figure 59, the register address portion gives the first register that will be written to. Subsequent data bytes will be written into sequential writable registers. Thus, after each data byte has been written into a register, the address pointer register autoincrements its value to the next available register. The address pointer register will autoincrement from 00h to 3Fh and will loop back to start again at 00h when it reaches 3Fh. Figure 60 to Figure 62 show the timing diagrams necessary to accomplish correct read operations. To read back from a register, first write to the address pointer register with the address of the register to be read from. This operation is shown in Figure 60. Figure 61 shows the procedure for reading back a single byte of data. The read command is first sent to the part during the first eight clock cycles. During the following eight clock cycles, the data contained in the register selected by the address pointer register is output onto the DOUT line. Data is output onto the DOUT line on the falling edge of SCLK. Figure 62 shows the procedure when reading data from two sequential registers. Multiple data reads are possible in the SPI interface mode as the address pointer register is autoincremental. The address pointer register will autoincrement from 00h to 3Fh and will loop back to start again at 00h when it reaches 3Fh. Rev. A | Page 36 of 40 ADT7518 CS 1 8 8 1 SCLK DIN D6 D7 D5 D3 D4 D2 D1 D7 D0 D6 D5 D4 D3 D2 D1 D0 START WRITE COMMAND REGISTER ADDRESS CS (CONTINUED) 1 8 SCLK (CONTINUED) D7 DIN (CONTINUED) D6 D4 D5 D3 D2 D1 D0 04879-059 STOP DATA BYTE Figure 59. SPI—Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register CS 1 8 8 1 SCLK DIN D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D2 D3 D1 D0 STOP WRITE COMMAND 04879-060 START REGISTER ADDRESS Figure 60. SPI—Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation CS 1 8 8 1 DIN D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X X DOUT X X X X X X X X D7 D6 D5 D4 D3 D2 D1 D0 STOP START DATA BYTE 1 READ COMMAND Figure 61. SPI—Reading a Single Byte of Data From a Selected Register Rev. A | Page 37 of 40 04879-061 SCLK ADT7518 CS 1 8 8 1 SCLK DIN DOUT D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X X X X X X X X X X D7 D6 D5 D4 D3 D2 D1 D0 START READ COMMAND DATA BYTE 1 CS (CONTINUED) 1 8 DIN (CONTINUED) X DOUT (CONTINUED) D7 X X X X X X X D6 D5 D4 D3 D2 D1 D0 04879-062 SCLK (CONTINUED) STOP DATA BYTE 2 Figure 62. SPI—Reading Two Bytes of Data From Two Sequential Registers SPI READ OPERATION WRITE OPERATION 04879-063 CS Figure 63. SPI—Correct Use of CS During SPI Communication SMBus/SPI INT/INT The ADT7518 INT/INT output is an interrupt line for devices that want to trade their ability to master for an extra pin. It is a slave device and uses the SMBus/SPI INT/INT to signal the host device that it wants to talk to. The SMBus/SPI INT/INT on the ADT7518 is used as an over/under limit indicator. The INT/INT pin has an open-drain configuration that allows the outputs of several devices to be wired-AND’ed together when the INT/INT pin is active low. Use C6 of the Control Config-uration 1 register to set the active polarity of the INT/INT out-put. The power-up default is active low. The INT/INT output can be disabled or enabled by setting C5 of the Control Config-uration 1 register to 1 or 0, respectively. The INT/INT output becomes active when either the internal temperature value, the external temperature value, VDD value, or any of the AIN input values exceed the values in their corresponding THIGH/VHIGH or TLOW/VLOW registers. The INT/INT output goes inactive again when a conversion result has the measured value back within the trip limits and when the status register associated with the out-of-limit event is read. The two interrupt status registers show which event caused the INT/INT pin to go active. The INT/INT output requires an external pull-up resistor. This can be connected to a voltage different from VDD, provided the maximum voltage rating of the INT/INT output pin is not exceeded. The value of the pull-up resistor depends on the application but should be large enough to avoid excessive sink currents at the INT/INT output, which can heat the chip and affect the temperature reading. SMBUS ALERT RESPONSE The INT/INT pin behaves the same way as an SMBus alert pin when the SMBus/I2C interface is selected. It is an open-drain output and requires a pull-up to VDD. Several INT/INT outputs can be wire-AND’ed together, so that the common line will go low if one or more of the INT/INT outputs goes low. The polarity of the INT/INT pin must be set active low for a number of outputs to be wire-AND’ed together. Rev. A | Page 38 of 40 ADT7518 of-limit event is read. If the SMBALERT line remains low, the master will send the ARA again. It will continue to do this until all devices whose SMBALERT outputs were low have responded. The INT/INT output can operate as an SMBALERT function. Slave devices on the SMBus cannot normally signal to the master that they want to talk, but the SMBALERT function allows them to do so. SMBALERT is used in conjunction with the SMBus general call address. START RD ACK DEVICE ADDRESS MASTER SENDS ARA AND READ COMMAND NO STOP ACK DEVICE SENDS ITS ADDRESS Figure 64. INT/INT Responds to SMBALERT ARA SMBALERT pulled low. 2. Master initiates a read operation and sends the alert response address (ARA = 0001 100). This is a general call address that must not be used as a specific device address. The devices whose INT/INT output is low responds to the alert response address and the master reads its device address. As the device address is seven bits long, an LSB of 1 is added. The address of the device is now known and it can be interrogated in the usual way. 4. If more than one device’s INT/INT output is low, the one with the lowest device address will have priority in accordance with normal SMBus specifications. 5. Once the ADT7518 has responded to the alert response address, it will reset its INT/INT output, provided that the condition that caused the out-of-limit event no longer exists and that the status register associated with the out- DEVICE ACK MASTER RECEIVES SMBALERT RESPONSE START ALERT ADDRESS Rev. A | Page 39 of 40 MASTER SENDS ARA AND READ COMMAND MASTER ACK DEVICE RD ACK ADDRESS ACK MASTER NACK PEC NO ACK DEVICE SENDS DEVICE SENDS ITS ADDRESS ITS PEC DATA Figure 65. INT/INT Responds to SMBALERT ARA With Packet Error Checking (PEC) STOP 04879-065 1. 3. ALERT RESPONSE ADDRESS 04879-064 One or more INT/INT outputs can be connected to a common SMBALERT line connected to the master. When the SMBALERT line is pulled low by one of the devices, the following procedure occurs, as shown in Figure 64. MASTER RECEIVES SMBALERT ADT7518 OUTLINE DIMENSIONS 0.193 BSC 9 16 0.154 BSC 1 0.236 BSC 8 PIN 1 0.069 0.053 0.065 0.049 0.010 0.025 0.004 BSC COPLANARITY 0.004 0.012 0.008 SEATING PLANE 0.010 0.006 8° 0° 0.050 0.016 COMPLIANT TO JEDEC STANDARDS MO-137AB Figure 66. 16-Lead Shrink Small Outline Package [QSOP] (RQ-16) Dimensions in Inches ORDERING GUIDE Model ADT7518ARQ ADT7518ARQ-REEL ADT7518ARQ-REEL7 ADT7518ARQZ1 ADT7518ARQZ-REEL1 ADT7518ARQZ-REEL71 1 Temperature Range –40°C to +120°C –40°C to +120°C –40°C to +120°C –40°C to +120°C –40°C to +120°C –40°C to +120°C DAC Resolution 8 Bits 8 Bits 8 Bits 8 Bits 8 Bits 8 Bits Package Description 16-Lead QSOP 16-Lead QSOP 16-Lead QSOP 16-Lead QSOP 16-Lead QSOP 16-Lead QSOP Package Option RQ-16 RQ-16 RQ-16 RQ-16 RQ-16 RQ-16 Minimum Quantities/Reel N/A 2,500 1,000 N/A 2,500 1,000 Z = Pb-free part. Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser 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. © 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C04879-0-8/04(A) Rev. A | Page 40 of 40