PRELIMINARY TECHNICAL DATA 4-Channel, 12-/10-Bit ADCs with I2C Compatible Interface in 16-Lead TSSOP AD7994/AD7993 Preliminary Technical Data a FEATURES 12-Bit ADC with Fast Conversion Time: 2 µs Four Single-Ended Analog Input Channels Specified for VDD of 2.7 V to 5.5 V Low Power Consumption Fast Throughput Rate:- 188 KSPS Sequencer Operation Automatic Cycle Mode I2CR Compatible Serial Interface I2CR Interface supports: Standard, Fast, and High-Speed Modes Out of Range Indicator/Alert Function Pin-Selectable Addressing via AS Two Versions Allow Five I2C Addresses Shutdown Mode: 1µA max 16-Lead TSSOP Package FUNCTIONAL BLOCK DIAGRAM VDD The AD7994/AD7993 provide a two-wire serial interface which is compatible with I2C interfaces. The parts come in two versions, AD7994-0/AD7993-0 to AD7994-1/ AD7993-1. Each version allows for a minimum of two different I2C addresses. The I2C interface on the AD79940/AD7993-0 supports Standard and Fast I2C Interface Modes. The I2C interface on the AD7994-1/AD7993-1 supports Standard, Fast and two High-Speed I2C Interface Modes. The AD7994/AD7993 normally remain in a shutdown state while not converting, powering up only for conversions. The conversion process can be controlled using the CONVST pin, an Automatic Conversion Cycle selected through software control, or a mode where conversions occur across Write operations. There are no pipeline delays associated with the part. The reference for the part is applied externally to the REFIN pin and can be in the range of 1.2V to VDD. This allows the widest dynamic input range to the ADC. CONVST REFIN AD7994/AD7993 VIN1 T/H VIN2 I/P MUX VIN3 12-/10-BIT SUCCESSIVE APPROXIMATION ADC CONTROL LOGIC VIN4 OSCILLATOR DATALOW LIMIT REGISTER CH1-CH4 CONVERSION RESULT REGISTER CONFIGURATION REGISTER DATAHIGH LIMIT REGISTER CH1-CH4 ALERT ALERT STATUS REGISTER HYSTERESIS REGISTER CH1-CH4 GENERAL DESCRIPTION The AD7994/AD7993 are 4 channel, 12-/10-bit, high speed, low power, successive-approximation ADCs respectively. They operate from a single 2.7 V to 5.5 V power supply and feature a conversion time of 2 µs. The parts contain a four channel multiplexer and track/hold amplifier which can handle input frequencies in excess of TBD kHz. GND CYCLE TIMER REGISTER AS I2C INTERFACE SCL SDA GND On-chip registers can be programmed with high and low limits for the conversion result, and an open drain Out of Range Indicator output (ALERT), becomes active when the programmed high or low limits are violated by the conversion result. This output can be used as an interrupt. PRODUCT HIGHLIGHTS 1. 2 µs Conversion time with low power consumption. 2. I2C Compatible Serial Interface with pin selectable addresses. Two AD7994/AD7993 versions allow five AD7994/AD7993 devices to be connected to the same serial bus. 3. The parts feature automatic shutdown while not converting to maximize power efficiency. Current consumption is 1µA max when in shutdown. 4. Reference can be driven up to the power supply. 5. Out of Range Indicator which can be software disabled/ enabled. 6. Oneshot and automatic conversion rates. 7. No Pipeline Delay The part features a standard successive-approximation ADC. SMBus is a trademark and I2C is a registered trademark of Philips Corporation REV. PrF 09/03 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 Analog Devices, Inc., 2003 PRELIMINARY TECHNICAL DATA AD7994–SPECIFICATIONS1 otherwise noted; T = T (VDD = +2.7 V to +5.5 V, unless otherwise noted ; REFIN = 2.5 V; fSCL = 3.4 MHz unless A MIN to TMAX, unless otherwise noted.) B Version1 Units 70 71 -78 -80 dB dB dB dB -78 -78 10 10 TBD TBD TBD dB typ dB typ ns max ps typ dB typ kHz typ kHz typ 12 ±1 ±0.6 +1.5/-0.9 ±0.75 ±1.5 ±0.5 ±1.5 ±0.5 Bits LSB LSB LSB LSB LSB LSB LSB LSB ANALOG INPUT Input Voltage Ranges DC Leakage Current Input Capacitance 0 to REFIN ±1 30 Volts µA max pF typ REFERENCE INPUT REFIN Input Voltage Range DC Leakage Current Input Capacitance Input Impedance 1.2 to VDD ±1 TBD TBD V min/Vmax µA max pF max k⍀ typ LOGIC Input Input Input Input Input 0.7(V DD ) 0.3(V DD ) ±1 10 TBD V min V max µA max pF max V min 2.4 2.0 0.8 0.4 ±1 10 V min V min V max V max µA max pF max Parameter DYNAMIC PERFORMANCE Signal to Noise + Distortion (SINAD)2 Signal to Noise Ratio (SNR)2 Total Harmonic Distortion (THD)2 Peak Harmonic or Spurious Noise (SFDR)2 Intermodulation Distortion (IMD)2 Second Order Terms Third Order Terms Aperture Delay Aperture Jitter Channel-to-Channel Isolation Full Power Bandwidth DC ACCURACY Resolution Integral Nonlinearity2 Differential Nonlinearity2 Offset Error2 Offset Error Match2 Gain Error2 Gain Error Match2 INPUTS (SDA, SCL) High Voltage, VINH Low Voltage, VINL Leakage Current, IIN Capacitance, CIN2,3 Hysteresis, VHYST LOGIC INPUT (CONVST) Input High Voltage, VINH Input Low Voltage, VINL Input Leakage Current, IIN Input Capacitance, CIN2,3 LOGIC OUTPUTS (OPEN DRAIN) Output Low Voltage, VOL Floating-State Leakage Current Floating-State Output Capacitance2,3 Output Coding Test Conditions/Comments FIN = 10kHz Sine Wave min min typ typ fa = TBD kHz, fb = TBD kHz max typ max typ max max max max 0.4 V max 0.6 V max ±1 µA max TBD pF max Straight (Natural) Binary FIN = TBD kHz @ 3 dB @ 0.1 dB Guaranteed No Missed Codes to 12 Bits. VIN = 0 V or VDD VDD = 5V VDD = 3 V VDD = 5V VDD = 3V VIN = 0 V or VDD ISINK = 3mA ISINK = 6mA . –2– REV. PrF PRELIMINARY TECHNICAL DATA = +2.7 V to +5.5 V, unless otherwise noted ; REF = 2.5 V; f AD7994–SPECIFICATIONS1 (Votherwise noted; T = T to T , unless otherwise noted.) DD IN A Parameter CONVERSION RATE Conversion Time Track/Hold Acquisition Time Throughput Rate POWER REQUIREMENTS VDD IDD Peak Current Power Down Mode , Interface Inactive Interface Active Operating, Interface Inactive Interface Active MIN SCL = 3.4 MHz unless MAX B Version1 Units 2 TBD TBD 3.4 13 79 µs typ ns max ns max KSPS max KSPS max KSPS max 2.7/5.5 V min/max TBD 0.2/0.6 0.05/0.2 0.3/0.8 µA max µA max mA max mA max Digital Inputs = 0 V or VDD Peak Current during conversion VDD = 3 V/5 V. VDD = 3 V/5 V 400 kHz SCL. VDD = 3 V/5 V 3.4 MHz SCL. 0.06/0.15 0.3/0.6 0.15/0.35 0.6/1.4 mA mA mA mA VDD VDD VDD VDD Test Conditions/Comments See Interface Section max max max max Full-Scale step input Sine wave input <= 30 Standard mode SCL = Fast Mode SCL = 400 High-Speed Mode SCL = = = = 3 3 3 3 V/5 V/5 V/5 V/5 V V V V KHz 100 kHz kHz = 3.4 MHz 400 kHz SCL. 3.4 MHz SCL. 400 kHz SCL. 3.4 MHz SCL. NOTES 1 Temperature ranges as follows: B Version: –40°C to +85°C. 2 See Terminology. 3 Sample tested @ +25°C to ensure compliance. 4 See POWER VERSUS THROUGHPUT RATE section. Specifications subject to change without notice. –3– REV. PrF PRELIMINARY TECHNICAL DATA = +2.7 V to +5.5 V, unless otherwise noted ; REF = 2.5 V; f AD7993–SPECIFICATIONS1 (Votherwise noted; T = T to T , unless otherwise noted.) DD IN A MIN B Version1 Units 61 TBD -73 -74 dB dB dB dB -78 -78 10 10 TBD TBD TBD dB typ dB typ ns max ps typ dB typ kHz typ kHz typ Differential Nonlinearity 2 10 ±1 ±0.6 ±0.9 Bits LSB max LSB typ LSB max Offset Error2 Offset Error Match2 Gain Error2 Gain Error Match2 Total Unadjusted Error (TUE)2 ±1 ±0.5 ±1 ±0.5 ±1 LSB LSB LSB LSB LSB ANALOG INPUT Input Voltage Ranges DC Leakage Current Input Capacitance 0 to REFIN ±1 30 Volts µA max pF typ REFERENCE INPUT REFIN Input Voltage Range DC Leakage Current Input Capacitance Input Impedance TBD/TBD ±1 TBD TBD V min/Vmax µA max pF max k⍀ typ LOGIC INPUTS (SDA, SCL, CONVST) Input High Voltage, VINH Input Low Voltage, VINL Input Leakage Current, IIN Input Capacitance, CIN2,3 Input Hysteresis, VHYST 0.7(V DD ) 0.3(V DD ) ±1 10 TBD V min V max µA max pF max V min 2.4 2.0 0.8 0.4 ±1 10 V min V min V max V max µA max pF max Parameter DYNAMIC PERFORMANCE Signal to Noise + Distortion (SINAD)2 Signal to Noise Ratio (SNR)2 Total Harmonic Distortion (THD)2 Peak Harmonic or Spurious Noise (SFDR)2 Intermodulation Distortion (IMD)2 Second Order Terms Third Order Terms Aperture Delay Aperture Jitter Channel-to-Channel Isolation Full Power Bandwidth DC ACCURACY Resolution Integral Nonlinearity2 LOGIC INPUT (CONVST) Input High Voltage, VINH Input Low Voltage, VINL Input Leakage Current, IIN Input Capacitance, CIN2,3 LOGIC OUTPUTS (OPEN DRAIN) Output Low Voltage, VOL Floating-State Leakage Current Floating-State Output Capacitance2,3 Output Coding SCL = 3.4 MHz unless MAX Test Conditions/Comments FIN = 10kHz Sine Wave min min typ typ fa = TBD kHz, fb = TBD kHz FIN = TBD kHz @ 3 dB @ 0.1 dB Guaranteed No Missed Codes to 10 Bits. max max max max max 0.4 V max 0.6 V max ±1 µA max TBD pF max Straight (Natural) Binary VIN = 0 V or VDD VDD = 5V VDD = 3 V VDD = 5V VDD = 3V VIN = 0 V or VDD ISINK = 3mA ISINK = 6mA . –4– REV. PrF PRELIMINARY TECHNICAL DATA AD7993–SPECIFICATIONS1 otherwise noted; T = T (VDD = +2.7 V to +5.5 V, unless otherwise noted ; REFIN = 2.5 V; fSCL = 3.4 MHz unless A MIN to TMAX, unless otherwise noted.) Parameter CONVERSION RATE Conversion Time Track/Hold Acquisition Time B Version1 Units 2 TBD TBD 3.4 13 79 µs typ ns max ns max KSPS max KSPS max KSPS max 2.7/5.5 V min/max TBD 0.2/0.6 0.05/0.2 0.3/0.8 mA max µA max mA max mA max Digital Inputs = 0 V or VDD Peak Current during conversion VDD = 3 V/5 V. VDD = 3 V/5 V 400 kHz SCL. VDD = 3 V/5 V 3.4 MHz SCL. 0.06/0.15 0.3/0.6 0.15/0.35 0.6/1.4 mA mA mA mA VDD VDD VDD VDD Test Conditions/Comments See Interface Section Throughput Rate POWER REQUIREMENTS VDD IDD Peak Current Power Down Mode , Interface Inactive Interface Active Operating, Interface Inactive Interface Active max max max max Full-Scale step input Sine wave input <= 30 KHz Standard mode 100 kHz Fast Mode 400 kHz High-Speed Mode 3.4 MHz = = = = 3 3 3 3 V/5 V/5 V/5 V/5 V V V V 400 kHz SCL. 3.4 MHz SCL. 400 kHz SCL. 3.4 MHz SCL. NOTES 1 Temperature ranges as follows: B Version: –40°C to +85°C. 2 See Terminology. 3 Sample tested @ +25°C to ensure compliance. 4 See POWER VERSUS THROUGHPUT RATE section. Specifications subject to change without notice. t11 t12 t2 t6 SCL t6 t4 t5 t3 t8 t1 t9 t10 SDA t7 P S S P S = START CONDITION P = STOP CONDITION Figure 1. Two-Wire Serial Interface Timing Diagram I2C TIMING SPECIFICATIONS1 Parameter fSCL t1 t2 t3 2 AD7994/AD7993 Limit at TMIN, TMAX MIN MAX Unit Conditions Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode Fast Mode High-Speed Mode (VDD = +2.7 V to +5.5 V, unless otherwise noted ; REFIN = 2.5 V; unless otherwise noted; TA = TMIN to TMAX, unless otherwise noted..) 100 400 3.4 1.7 CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max 4 0.6 60 120 4.7 1.3 160 320 250 100 10 –5– kHz kHz MHz MHz µs µs ns ns µs µs ns ns ns ns ns Description Serial Clock Frequency tHIGH, SCL High Time tLOW, SCL Low Time tSU;DAT, Data Setup Time REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 I2C TIMING SPECIFICATIONS1 (Continued.) Parameter Conditions t4 Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode t5 Fast Mode High-Speed Mode Standard Mode t6 Fast Mode High-Speed Mode Standard Mode t7 Fast Mode t8 Standard Mode Fast Mode High-Speed Mode Standard Mode t9 Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode t 10 Fast Mode High-Speed Mode, High-Speed Mode, t 11 Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, t 11A Standard Mode Fast Mode High-Speed Mode, High-Speed Mode, Standard Mode t 12 Fast Mode High-Speed Mode, High-Speed Mode, t SP 4 Fast Mode High-Speed Mode t POWER-UP CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max CB = 100pF max CB = 400pF max AD7994/AD7993 Limit at TMIN, TMAX MIN MAX 0 3.45 0 0.9 0 70 0 150 4.7 0.6 160 4 0.6 160 4.7 1.3 4 0.6 160 1000 20 + 0.1CB 300 10 80 20 160 300 20 + 0.1CB 300 10 80 20 160 1000 20 + 0.1CB 300 10 40 20 80 1000 20 + 0.1CB 300 10 80 20 160 300 20 + 0.1CB 300 10 40 20 80 0 50 0 10 1 Unit µs µs ns ns µs µs ns µs µs ns µs µs µs µs ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns µs Description t HD;DAT, Data Hold Time tSU;STA, Set-up Time for a repeated START Condition t HD;STA, Hold Time (repeated) START Condition tBUF, Bus Free Time Between a STOP and a START Condition. tSU;STO, Set-up Time for STOP Condition tRDA, Rise time of SDA signal tFDA, Fall time of SDA signal tRCL, Rise time of SCL signal tRCL1, Rise time of SCL signal after a repeated START Condition and after an Acknowledge bit. tFCL, Fall Time of SCL signal Pulsewidth of Spike Suppressed. Power-up Time NOTES 1 See Figure 1. C B refers to the capacitance load on the bus line. Hs-Mode timing specifications apply to the AD7994-1/AD7993-1 only. Standard and Fast Mode timing specifications apply to both the AD7994-0/AD7993-0 and the AD7994-1/AD7993-1. 2 The SDA and SCL timing is measured with the input filters enabled. Switching off the input filters improves the transfer rate but has a negative effect on EMC behavior of the part. 4 Input filtering on both the SCL and SDA inputs suppress noise spikes that are less than 50ns or 10ns for Fast Mode or High-Speed mode respectivley. Specifications subject to change without notice. –6– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 ABSOLUTE MAXIMUM RATINGS1 (TA = +25°C unless otherwise noted) VDD to GND –0.3 V to 7 V Analog Input Voltage to GND –0.3 V to VDD + 0.3 V Reference Input Voltage to GND -0.3 V to VDD + 0.3 V Digital Input Voltage to GND –0.3 V to 7 V Digital Output Voltage to GND –0.3 V to VDD + 0.3 V Input Current to Any Pin Except Supplies2 ±10 mA Operating Temperature Range Commercial (B Version) –40°C to +85°C Storage Temperature Range –65°C to +150°C Junction Temperature 16-ld TSSOP Package θJA Thermal Impedance θJC Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 secs) Infared (15 secs) +150°C 150.4°C/W (TSSOP) 27.6°C/W (TSSOP) +215°C +220°C NOTES 1 Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 Transient currents of up to 100 mA will not cause SCR latch up. ORDERING GUIDE Model 1 AD7994BRU-0 AD7994BRU-1 AD7993BRU-0 AD7993BRU-1 Temperature Range -40°C -40°C -40°C -40°C to to to to Linearity Error2(max) Package Option3 +85°C +85°C +85°C +85°C ±1 ±1 ±1 ±1 LSB LSB LSB LSB RU-16 RU-16 RU-16 RU-16 NOTES 1 The AD7994-0/AD7993-0 supports Standard and Fast I 2 C interface modes. The AD7994-1/AD7993-1 supports Standard, Fast and Highspeed I 2C Interface Modes. 2 Linearity error here refers to Integral Nonlinearity 3 RU = TSSOP. 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 the AD7994/AD7993 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. PrF –7– PRELIMINARY TECHNICAL DATA AD7994/AD7993 PIN FUNCTION DESCRIPTION Pin Mnemonic AGND VDD REF IN V IN 1 V IN 3 V IN 4 V IN 2 AS CONVST ALERT/BUSY SDA SCL Function Analog Ground. Ground reference point for all circuitry on the AD7994/AD7993. All analog input signals should be referred to this GND voltage. Power Supply Input. The VDD range for the AD7994/AD7993 is from +2.7V to +5.5V. Voltage Reference Input. The External Reference for the AD7994/AD7993 should 0.1 µF capacitor should be placed between the REFIN pin and AGND. Analog Input 1. Single-ended analog input channel. The input range is 0V to REFIN. Analog Input 3. Single-ended analog input channel. The input range is 0V to REFIN. Analog Input 4. Single-ended analog input channel. The input range is 0V to REFIN. Analog Input 2. Single-ended analog input channel. The input range is 0V to REFIN. Logic Input. Address Select Input which selects one of three I2C addresses for the AD7994/ AD7993 as shown in Table I. Logic Input Signal. Convert Start Signal. This is an edge triggered logic input. The rising edge of this signal powers up the part. The power up time for the part is 1µs. The falling edge of CONVST places the track/hold into hold mode and initiates a conversion. A power up time of at least 1µs must be allowed for the CONVST high pulse, otherwise the conversion result will be invalid. (See Modes of Operation Section) Digital Output, selectable as an ALERT or BUSY output function. When configured as an ALERT output, this pin acts as an Out of Range Indicator, and if enabled becomes active when the conversion result violates the DATAHIGH or DATALOW values. See Limit Registers section. When configured as a BUSY output, this pin becomes active when a conversion is in progress. Digital I/O. Serial Bus Bi-directional Data. Open-drain output. External pull-up resistor required. Digital Input. Serial Bus Clock. External pull-up resistor required. AD7994/AD7993 PIN CONFIGURATION TSSOP AGND 1 AGND 2 AGND 3 AGND 4 AD7994 16 AGND 15 SCL 14 SDA TOP VIEW 13 ALERT (Not to Scale) 12 CONVST VDD 5 REFIN 6 11 AS VIN1 7 10 VIN2 VIN3 8 9 VIN4 –8– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 Table I. I2C Address Selection AS Pin I2C Address AD7993-0 AD7993-0 AD7993-1 AD7993-1 GND V DD GND V DD 010 010 010 010 AD7993-X 1 Float 010 0000 Part Number 0001 0010 0011 0100 Note:1. If the AS pin is left floating on any of the AD7993 parts the device address will be 010 0000 AS Pin I2C Address AD7994-0 AD7994-0 AD7994-1 AD7994-1 GND V DD GND V DD 010 010 010 010 AD7994-X 1 Float 010 0000 Part Number 0001 0010 0011 0100 Note :1. If the AS pin is left floating on any of the AD7994 parts the device address will be 010 0000 REV. PrF –9– PRELIMINARY TECHNICAL DATA AD7994/AD7993 TERMINOLOGY Channel-to-Channel Isolation Signal to (Noise + Distortion) Ratio Channel-to-Channel Isolation is a measure of the level of crosstalk between channels. It is measured by applying a fullscale TBD kHz sine wave signal to the nonselected input channels and determining how much the TBD kHz signal is attenuated in the selected channel. This figure is This is the measured ratio of signal to (noise + distortion) at the output of the A/D converter. The signal is the rms amplitude of the fundamental. Noise is the sum of all nonfundamental signals up to half the sampling frequency (fS/2), excluding dc. The ratio is dependent on the number of quantization levels in the digitization process; the more levels, the smaller the quantization noise. The theoretical signal to (noise + distortion) ratio for an ideal Nbit converter with a sine wave input is given by: Signal to (Noise + Distortion) = (6.02 N + 1.76) dB Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the rms sum of harmonics to the fundamental. For the AD7994/ AD7993, it is defined as: 2 2 2 This is the measured interval between the leading edge of the sampling clock and the point at which the ADC actually takes the sample. Aperture Jitter This is the sample-to-sample variation in the effective point in time at which the sample is taken. Thus for a 12-bit converter, this is 74 dB THD (dB ) = 20 log given worse case across all channels. Aperture Delay 2 2 V2 +V3 +V 4 +V5 +V 6 V1 where V1 is the rms amplitude of the fundamental and V2, V3, V4 , V5 and V6 are the rms amplitudes of the second through the sixth harmonics. Peak Harmonic or Spurious Noise Peak harmonic or spurious noise is defined as the ratio of the rms value of the next largest component in the ADC output spectrum (up to fS/2 and excluding dc) to the rms value of the fundamental. Normally, the value of this specification is determined by the largest harmonic in the spectrum, but for ADCs where the harmonics are buried in the noise floor, it will be a noise peak. Intermodulation Distortion With inputs consisting of sine waves at two frequencies, fa and fb, any active device with nonlinearities will create distortion products at sum and difference frequencies of mfa ± nfb where m, n = 0, 1, 2, 3, etc. Intermodulation distortion terms are those for which neither m nor n are equal to zero. For example, the second order terms include (fa + fb) and (fa – fb), while the third order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb). The AD7994/AD7993 is tested using the CCIF standard where two input frequencies near the top end of the input bandwidth are used. In this case, the second order terms are usually distanced in frequency from the original sine waves while the third order terms are usually at a frequency close to the input frequencies. As a result, the second and third order terms are specified separately. The calculation of the intermodulation distortion is as per the THD specification where it is the ratio of the rms sum of the individual distortion products to the rms amplitude of the sum of the fundamentals expressed in dBs. Full Power Bandwidth The Full Power Bandwidth of an ADC is that input frequency at which the amplitude of the reconstructed Fundamental is reduced by 0.1 dB or 3 dB for a full-scale input PSRR (Power Supply Rejection) The power supply rejection ratio is defined as the ratio of the power in the ADC output at full-scale frequency, f, to the power of a 200 mV p-p sine wave applied to the ADC VDD supply of frequency fs. PSRR (dB) = 10 log (Pf/Pfs) Pf is the power at frequency f in the ADC output; Pfs is the power at frequency fs coupled into the ADC VDD supply. Integral Nonlinearity This is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale, a point 1 LSB below the first code transition, and full scale, a point 1 LSB above the last code transition. Differential Nonlinearity This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC. Offset Error This is the deviation of the first code transition (00 . . . 000) to (00 . . . 001) from the ideal, i.e AGND + 1LSB Offset Error Match This is the difference in offset error between any two channels. Gain Error This is the deviation of the last code transition (111 . . . 110) to (111 . . . 111) from the ideal (i.e., REFIN – 1 LSB) after the offset error has been adjusted out. Gain Error Match This is the difference in Gain error between any two channels. –10– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 AD7994/AD7993 TYPICAL PERFORMANCE CURVES TPC 1 shows a typical FFT plot for the AD7994 at TBD kSPS sample rate and TBD kHz input frequency. TPC 1. AD7994 Dynamic Performance at TBD ksps. TPC 2. AD7993 Dynamic Performance at TBD ksps. TPC 3. PSRR vs Supply Ripple Frequency. TPC 4. AD7994 SINAD vs Analog Input Frequency for Various Supply Voltages at TBD ksps. TPC 5. AD7994 Typical INL VDD = 5V. TPC 6. AD7994 Typical DNL VDD = 5V. TPC 7. AD7994 Typical INL VDD = 3V. TPC 8. AD7994 Typical DNL VDD = 3V. REV. PrF –11– TPC 9. AD7994 Change in INLvs Reference Voltage VDD = 5V. PRELIMINARY TECHNICAL DATA AD7994/AD7993 TPC 10. AD7994 Change in DNL vs Reference Voltage. TPC 11. AD7994 Shutdown Current vs Supply Voltage, -40 , 25 and 85 °C. TPC 13. AD7994 Supply Current vs Supply Voltage for Various Temperatures. TPC 14. AD7994 ENOB vs Reference Voltage, VDD = 3V and VDD = 5V. –12– TPC 12. AD7994 Supply Current vs I2C Bus Rate for VDD = 3V and 5V. REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 CIRCUIT INFORMATION CAPACITIVE DAC The AD7994/AD7993 are fast, low-power, 12-/10-bit, single supply, 4 Channel A/D converters respectively. The parts can be operated from a 2.7 V to 5.5 V supply. The AD7994/AD7993 will normally remain in a powerdown state while not converting. When supplies are first applied the part will come up in a shutdown state. Powerup is intitiated prior to a conversion and the device returns to power-down upon completion of the conversion. Conversions can be initiated on the AD7994/AD7993 by either pulsing the CONVST signal, using an automatic cycling mode or using a mode where wake-up and conversion occur during the write function ( see modes of Operation section). On completion of a conversion the AD7994/ AD7993 will enter shutdown mode again. This automatic shutdown feature allows power saving between conversions. This means any read or write operations across the I2C interface can occur while the device is in shut-down. A VIN CONTROL LOGIC SW1 B SW2 COMPARATOR AGND Figure 3. ADC Conversion Phase ADC TRANSFER FUNCTION The output coding of the AD7994/AD7993 is straight binary. The designed code transitions occur at successive integer LSB values (i.e., 1LSB, 2LSBs, etc.). The LSB size for the AD7994 is = REFIN/4096 and REFIN/256 for the AD7993 . The ideal transfer characteristic for the AD7994/AD7993 is shown in Figure 4 below. 111...111 111...110 ADC CODE The AD7994/AD7993 provide the user with a 4-channel multiplexer, an on-chip track/hold, A/D converter, an onchip oscillator, internal data registers and an I2C compatible serial interface, all housed in a 16-lead TSSOP package, which offers the user considerable space saving advantages over alternative solutions. An external reference is required by the AD7994/AD7993, and this reference can be in the range of 1.2 V to VDD. 111...000 011...111 AD7994 1 LSB = REFIN/4096 AD7993 1 LSB = REFIN/256 000...010 000...001 000...000 AGND +1 LSB ANALOG INPUT 0 V TO REFIN CONVERTER OPERATION The AD7994/AD7993 are successive approximation analog-to-digital converters based around a capacitive DAC. Figures 2 and 3 show simplified schematics of the ADC during its acquisition and conversion phase respectively. Figure 2 shows the ADC during its 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 VINX. Figure 4. AD7994/AD7993 Transfer Characteristic TYPICAL CONNECTION DIAGRAM Figure 5 shows the typical connection diagram for the AD7994/AD7993. In Figure 5 the Address Select pin, AS, is tied to VDD, however AS can also be either tied to GND or left floating, allowing the user to select up to three AD7994/AD7993 devices on the same serial bus. An external reference must be applied to the AD7994/ AD7993. This reference can be in the range of 1.2 V to VDD. A precision reference like the REF 19X family, ADR421, ADR03, ADR381 can be used to supply the Reference Voltage to the ADC. CAPACITIVE DAC A VIN CONTROL LOGIC SW1 B SW2 SDA and SCL form the two-wire I2C/SMBus compatible interface. External Pull-up resistors should be added to the SDA and SCL bus lines. COMPARATOR AGND Figure 2. ADC Acquisition Phase When the ADC starts a conversion, see Figure 3, SW2 will open and SW1 will move to position B causing the comparator to become unbalanced. The input is disconnected once the conversion begins. The Control Logic and the Capacitive 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 4 shows the ADC transfer function. REV. PrF +REFIN -1LSB The AD7994-0/AD7993-0 support Standard and Fast I2C Interface Modes. While the AD7994-1/AD7993-1 support Standard, Fast and High-speed I2C Interface Modes. Therefore if operating the AD7994/AD7993 in either Standard or Fast Mode, up to five AD7994/AD7993 devices (3 x AD7994-0/AD7993-0 and 2 x AD7994-1/ AD7993-1 or 3 x AD7994-1/AD7993-1 and 2 x AD79940/AD7993-0) can be connected to the bus. When operating in Hs-Mode then up to three AD7994-1/AD7993-1 devices can be connected to the bus. Wake-up from power-down prior to a conversion is approximately 1µs while conversion time is approximately 2µs. The AD7994/AD7993 enters power-down mode again after each conversion, this will be useful in applications where power consumption is of concern. –13– PRELIMINARY TECHNICAL DATA AD7994/AD7993 +5V SUPPLY 10µF 0.1µF RP 0V to REFIN INPUT VIN1 VIN2 VIN3 VIN4 VDD AD7994/ AD7993 RP RP TWO WIRE SERIAL INTERFACE SDA µC/µP SCL ALERT CON VST REFIN REF 19X GND SET TO REQUIRED ADDRESS AS 0.1µF Figure 5 AD7994/AD7993 Typical Connection Diagram Analog Input Figure 6 shows an equivalent circuit of the analog input sturcture of the AD7994/AD7993. The two diodes D1 and D2 provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal never exceeds the supply rails by more than 300mV. This will cause these diodes to become forward biased and start conducting current into the substrate. 10 mA is the maximum current these diodes can conduct without causing irreversable damage to the part. The capacitor C1 in Figure 6 is typically about 4pF and can primarily be attributed to pin capacitance. The resistor R1 is a lumped component made up of the on resistance (RON) of a switch(track and hold switch) and also includes the RON of the input multiplexer. The total resistance is typically about 400Ω. The capacitor C2 is the ADC sampling capacitor and has a capacitance of 30 pF typically. For ac applications, removing high frequency components from the analog input signal is recommended by use of an RC band-pass filter on the relevant analog input pin. In applications where harmonic distortion and signal to noise ratio are critical the analog input should be driven from a low impedance source. Large source impedances will significantly affect the ac performance of the ADC. This may necessitate the use of an input buffer amplifier. The choice of the op amp will be a function of the particular application. maximum source impedance will depend on the amount of total harmonic distortion (THD) that can be tolerated. The THD will increase as the source impedance increases and performance will degrade. Figure 7 shows a graph of the Total Harmonic Distortion vs. analog input signal frequency for different source impedances when using a supply voltage of 3V±10% and 5V±10% and sampling at a rate of xkSPS. Figure 8 shows a graph of the total harmonic distortion versus analog input signal frequency for various supply voltages while sampling at xkSPS . Figure 7. THD vs. Analog Input Frequency for Various Source Impedance for VDD= 3V and 5V When no amplifier is used to drive the analog input the source impedance should be limited to low values. The VDD D1 R1 C2 16PF VIN C1 4PF D2 CONVERSION PHASE - SWITCH OPEN TRACK PHASE - SWITCH CLOSED Figure 8. THD vs. Analog Input Frequency, Fs = xkSPS Figure 6. Equivalent Analog Input Circuit –14– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 INTERNAL REGISTER STRUCTURE ADDRESS POINTER REGISTER The AD7994/AD7993 contains seventeen internal registers, as shown in Figure 9, that are used to store conversion results, high and low conversion limits, and to configure and control the device. Sixteen are data registers and one is an address pointer register. The Address Pointer register itself does not have, nor does it require, an address, as it is the register to which the first data byte of every Write operation is written automatically. The Address Pointer Register is an 8-bit register in which the four LSBs are used as pointer bits to store an address that points to one of the data registers of the AD7994/ AD7993, while the four MSBs are used as command bits when operating in Mode 2 (see Modes of Operation section). The first byte following each write address is the address of one of the data registers, which is stored in the Address Pointer Register, and selects the data register to which subsequent data bytes are written. Only the four LSBs of this register are used to select a data register. On Power up the Address Point register contains all 0’s, pointing to the Conversion Result Register. CONVERSION RESULT REGISTER ALERT STATUS REGISTER CONFIGURATION REGISTER CYCLE TIMER REGISTER Table II. Address Pointer Register DATALOW REGISTER CH1 DATAHIGH REGISTER CH1 HYSTERESIS REGISTER CH1 ADDRESS POINTER REGISTER DATALOW REGISTER CH2 C3 C2 C1 0 0 0 0 D A T A P3 P2 P1 P0 Register Select Table III. AD7994/AD7993 Register Addresses DATAHIGH P3 P2 P1 P0 0 0 0 0 Conversion Result Register (Read) 0 0 0 1 Alert Status Register (Read/Write) 0 0 1 0 Configuration Register (Read/Write) REGISTER CH3 0 0 1 1 Cycle Timer Register (Read/Write) HYSTERESIS REGISTER CH3 0 1 0 0 DATALOW Reg CH1 (Read/Write) 0 1 0 1 DATA HIGH Reg CH1 (Read/Write) 0 1 1 0 Hysteresis Reg CH1 (Read/Write) REGISTER CH4 0 1 1 1 DATALOW Reg CH2 (Read/Write) HYSTERESIS REGISTER CH4 1 0 0 0 DATA HIGH Reg CH2 (Read/Write) 1 0 0 1 Hysteresis Reg CH2 (Read/Write) 1 0 1 0 DATALOW Reg CH3 (Read/Write) 1 0 1 1 DATA HIGH Reg CH3 (Read/Write) 1 1 0 0 Hysteresis Reg CH3 (Read/Write) 1 1 0 1 DATALOW Reg CH4 (Read/Write) 1 1 1 0 DATA HIGH Reg CH4 (Read/Write) 1 1 1 1 Hysteresis Reg CH4 (Read/Write) REGISTER CH2 HYSTERESIS REGISTER CH2 DATALOW REGISTER CH3 DATAHIGH DATALOW REGISTER CH4 DATAHIGH SDA SERIAL BUS INTERFACE SCL Figure 9. AD7994/AD7993 Register Structure Each data register has an address which is pointed to by the Address Pointer register when communicating with it. The Conversion Result Register is the only data register that is read only. REV. PrF C4 –15– Registers PRELIMINARY TECHNICAL DATA AD7994/AD7993 CONFIGURATION REGISTER The Configuration Register is an 8-bit read/write register that is used to set the operating modes of the AD7994/ AD7993. The bit functions of all 8 bits of the Configuration Register are outlined in Table IV. Table IV. D7 D6 D5 D4 CH4 CH3 CH2 CH1 0* 0* 0* 0* Configuration Register Bit Function Description D3 D2 D1 D0 FLTR ALERT EN BUSY/ALERT ALERT/BUSY POLARITY 1* 0* 0* 0* *Default settings at Power-up Bit Mnemonic Comment D7-D4 CH4-CH1 These four channel address bits select the analog input channel(s) to be converted on. A 1 in any of bits D7 to D4 selects a channel for conversion. If more than one channel bit is set to 1 then the AD7994/AD7993 will sequence through the selected channels, starting with the lowest channel. All unused channels should be set to zero. Table V shows how these four channel address bits are decoded. Prior to initiating a conversion a channel(s) must be selected in the Configuration Register. D3 FLTR The value written to this bit of the Control Register determines whether the filtering on SDA and SCL is enabled or to be bypassed. If this bit is a 1 then the the filtering is enabled, if it is a 0, then the filtering is bypassed. D2 ALERT EN The hardware ALERT function is enabled if this bit is set to 1 and disabled if set to 0. This bit is used in conjunction with the BUSY/ALERT bit to determine if the ALERT/BUSY pin will act as an ALERT or a BUSY output. (See Table VI.) D1 BUSY/ALERT This bit is used in conjunction with the ALERT EN bit to determine if the ALERT/BUSY output, pin 13, will act as an ALERT or BUSY output (see TABLE V1), or if pin 13 is configured as an ALERT output pin, if it is to be reset. When reading the Configuration registerD1 will always be a 0 when D2 is a 1. D0 BUSY/ALERT This bit determines the active polarity of the ALERT/BUSY pin regardless of whether it is POLARITY configured as an ALERT or BUSY output. It is active low if this bit is set to 0, and it is active high if set to 1. –16– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 Table V. Channel Selection D7 D6 D5 D4 Analog Input Channel 0 0 0 0 No channel selected, see Address Pointer Byte, Mode 2 0 0 0 1 Convert on VIN1 0 0 1 0 Convert on VIN2 0 0 1 1 Sequence between VIN1 and VIN2 0 1 0 0 Convert on VIN3 0 1 0 1 Sequence between VIN1 and VIN3 0 1 1 0 Sequence between VIN2 and VIN3 0 1 1 1 Sequence between VIN1, VIN2 and VIN3 1 0 0 0 Convert on VIN4 1 0 0 1 Sequence between VIN1 and VIN4 1 0 1 0 Sequence between VIN2 and VIN4 1 0 1 1 Sequence between VIN1, VIN2 and VIN4 1 1 0 0 Sequence between VIN3 and VIN4 1 1 0 1 Sequence between VIN1, VIN3 and VIN4 1 1 1 0 Sequence between VIN2, VIN3 and VIN4 1 1 1 1 Sequence between VIN1, VIN2, VIN3 and VIN4 Note 1:- The AD7994/AD7994 converts on the selected channel in the Sequence in ascending order, starting with the lowest channel in the sequence. Table VIIb. Conversion Value Register (Second Read) Table VI. ALERT/BUSY Function D2 D1 ALERT/BUSY Pin Configuration D7 D6 D5 D4 D3 D2 D1 D0 0 0 Pin does not provide any interrupt signal. B7 B6 B5 B4 B3 B2 B1/0 B0/0 0 1 Pin configured as a BUSY output. 1 0 Pin configured as an ALERT output. 1 1 Resets ALERT output pin, Alert_Flag bit in Conversion Result Reg, and entire Alert Status Reg ( if any active). The AD7994/AD7993 conversion result consists of an Alert_Flag bit, a leading zero, two Channel Identifier bits and the 12-/10- bit data result. For the AD7993 the two LSBs (D1 and D0) of the second read will contain two zeros. The Alert_Flag bit indicates whether the conversion result being read or any other channel result has violated the limit registers associated with it. The Master may wish to read the ALERT Status register to obtain more information on where the ALERT occurred if this Alert_Flag bit is set. This is followed by a leading zero and the two Channel Indentifier bits indicating which channel the conversion result corresponds to. The 12-/10-bit conversion result then follows MSB first. If 1/1 is written to bits D2/D1 in the configuration Register to reset the ALERT pin, the Alert Flag bit and the Alert Status Register; the contents of the Configuration Register will read 1/0 for D2/D1 respectively if read back. CONVERSION RESULT REGISTER The Conversion Result Register is a 16-bit read-only register which stores the conversion result from the ADC in Straight Binary format. A Two Byte read is necessary to read data from this register. Table VIIa shows the contents of the first byte to be read while Table VIIb show the contents of the second byte to be read from AD7994/ AD7993. Table VIIa. D15 D14 Conversion Value Register (First Read) D13 Alert_Flag Zero CH REV. PrF ID1 D12 CH D11 ID0 D10 D9 D8 M S B B10 B9 B8 Alert_Flag1 Zero CH ID1 CH ID0 Channel# Result 0/1 0 0 0 Channel 1(V IN1) 0/1 0 0 1 Channel 2(V IN2) 0/1 0 1 0 Channel 3(V IN3) 0/1 0 1 1 Channel 4(V IN4) –17– PRELIMINARY TECHNICAL DATA AD7994/AD7993 LIMIT REGISTERS the 12-bit Hysteresis register associated with that channel. The ALERT pin can also be reset by writing to bit D2,D1 in the Configuration Register. For the AD7993 D1 and D0 of the DATALOW register should contain 0’s. The AD7994/AD7993 has four pairs of limit registers, each to store high and low conversion limits for each analog input channel. Each pair of limit registers has one associated hysteresis register. All twelve registers are 16bits wide, only the 12 LSBs of the Registers are used for the AD7994/AD7993, However on the AD7993 the 2 LSBs, D1 and D0, should contain 0s. On power-up, the contents of the DATAHIGH Register for each channel will be fullscale, while the contents of the DATALOW registers will be zeroscale by default. The Limit Registers can be used to monitor the conversion results on each on the Analog input channels. The AD7994/AD7993 will signal an Alert ( in either hardware or software or both depending on configuration) if the result moves outside the upper or lower limit set by the limit registers. Table IXa. D15 DATALOW Register (First Read/Write) D14 Alert_Flag 0 Table IXb. D13 D12 D11 D10 D9 D8 0 B11 B10 B9 B8 0 DATALOW Register (Second Read/Write) D7 D6 D5 D4 D3 D2 D1 D0 B7 B6 B5 B4 B3 B2 B1 B0 DATA HIGH REGISTER CH1/CH2/CH3/CH4 HYSTERESIS REGISTER (CH1/CH2/CH3/CH4) The DATAHIGH Register for each channel is a 16-bit read/ write register, only the 12 LSBs of the Register are used. The Registers store the upper limit that will activate the ALERT output and/or the Alert_Flag bit in the Conversion Result Register. Therefore, if the value in the Conversion Result Register is greater than the value in the DATAHIGH Register, then the Alert_Flag bit is set to 1 and the ALERT pin is activated (the latter is true if ALERT is enabled in the Configuration Register). When the conversion result returns to a value at least N LSBs below the DATAHIGH Register value the ALERT output pin and Alert_Flag bit will be reset. The value of N is taken from the 12-bit Hysteresis register associated with that channel. The ALERT pin can also be reset by writing to bits D2, D1 in the Configuration Register. For the AD7993, D1 and D0 of the DATAHIGH register should contain 0’s. Each Hysteresis Register is a 16-bit read/write register, only the 12 LSBs of the register are used. The Registers store the hysteresis value, N when using the limit registers. Each pair of Limit registers has a dedicated hysteresis register. The hysteresis value determines the reset point for the ALERT pin/Alert_Flag if a violation of the limits has occurred. If a hysteresis value of say 8 LSBs is required on the upper and lower limits of channel 1 then the 12 bit word, 0000 0000 0000 1000, should be written to the Hysteresis Register CH1, the address of which is shown in Table III. On power up, the Hysteresis Registers will contain a value of 8 LSBs for the AD7994 and 2 LSBs for the AD7993. If a different hysteresis value is required then that value must be written to the Hysteresis Register for the channel in question. For the AD7993 D1 and D0 of the Hysteresis Register should contain 0’s. Table Xa. Table VIIIa. D15 DATAHIGH Register (First Read/Write) D14 Alert_Flag 0 D13 D12 D11 D10 D9 D8 0 B11 B10 B9 B8 0 D15 D14 Alert_Flag 0 Table Xb. Table VIIIb. DATAHIGH Register (Second Read/Write) D7 D6 D5 D4 D3 D2 D1 D0 B7 B6 B5 B4 B3 B2 B1 B0 Hysteresis Register (First Read/Write) DATALOW REGISTER CH1/CH2/CH3/CH4 The DATALOW Register for each channel is a 16-bit read/ write register, of which only the 12 LSBs are used. The Register stores the lower limit that will activate the ALERT output and/or the Alert_Flag bit in the conversion result register. Therefore, if the value in the Conversion Result Register is less than the value in the DATALOW Register, then the Alert_Flag bit is set to 1 and the ALERT pin is activated (the latter is true if ALERT is enabled in the Configuration Register). When the Conversion result returns to a value at least N LSBs above the DATALOW Register value the ALERT ouput pin and Alert_Flag bit will be reset. The value of N is taken from D13 D12 D11 D10 D9 D8 0 B11 B10 B9 B8 0 Hysteresis Register (Second Read/Write) D7 D6 D5 D4 D3 D2 D1 D0 B7 B6 B5 B4 B3 B2 B1 B0 Using the Limit Registers to Store Min/Max Conversion Results If fullscale, i.e. all 1s, is written to the Hysteresis register for a particular channel then the DATAHIGH and DATALOW Registers for that channel will no longer act as Limit registers as previously described, but instead they will act as storage registers for the maximum and minimum conversion results returned from conversions on a channel over any given period of time. This function is useful in applications where the widest span of actual conversion results is required rather than using the ALERT to signal an intervention is necessary, e.g. monitoring temperature extremes during refrigerated goods transportation. When using the limit registers to store the min and –18– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 max conversion results, the Alert_Flag bit, D15, can be used to indicate that an alert has happened on another one of the Input channels. It must be noted that on power-up, the contents of the DATAHIGH register for each channel will be fullscale, while the contents of the DATALOW registers will be zeroscale, by default minimum and maximum conversion values being stored in this way will be lost if power is removed or cycled. When using the limit registers to store the min and max conversion results, the Alert_Flag bit, D15, is used to indicate that an alert has happened on another one of the Input channels. If the Alert_Flag bit is set to 1, it will be reset when the Conversion result returns to a value at least N LSBs above the DATALOW Register value or below the DATALOW Register value or if bits D2 and D1 of the Configuration Register are set to 1. The Alert_Flag bit in the limit registers is useful if the user is not reading from the conversion result register when reading the min and max conversion results from the limit registers. ALERT STATUS REGISTER The Alert Status Register is a 8-bit read/write register, which provides information on an Alert event. If a conversion results in activating the ALERT pin or the Alert_Flag bit in the Conversion Result Register, as described in the Limit Registers section, then the Alert Status Register may be read to gain further information. It contains 2 status bits per channel, one corresponding to the DATAHIGH limit and the other to the DATALOW limit. Whichever bit has a status of 1 will show where the violation occured, i.e. on which channel and whether on upper or lower limit. If a second alert event occurs on the other channel between receiving the first alert and interrogating the Alert Status register then the corresponding bit for that Alert event will be set also. The entire contents of the Alert Status register may be cleared by writing 1,1, to bits D2 and D1 in the Configuration register as shown in Table VI. This may also be acheived by ‘writing’ all 1’s to the Alert Status Register itself. This means that if the Alert Status Register is addressed for a write operation which is all 1’s, then the contents of the Alert Status Register will then be cleared or resest to all 0’s. Alternatively, an individual active Alert bit(s) may be reset within the Alert Status Register by performing a write of ‘1’ to that bit alone. The advantage of this is that once an Alert event has been serviced, that particular bit can be reset, e.g. CH1LO, without clearing the entire contents of the Alert Status Register, thus preserving the status of any additional Alert, e.g. CH2HI, which may have occured while servicing the first. If it is not necessary to clear an Alert directly after servicing then obviously the Alert Status register may be read again immediately to look for any new Alerts, bearing in mind that the one just serviced will still be active. Table XIb. Alert Status Register Bit Function Description Bit Mnemonic Comment D 0 CH1 LO Violation of DATALOW limit on Channel 1 if this bit set to 1, no violation if 0. D 1 CH1 HI Violation of DATAHIGH limit on Chan nel 1 if this bit set to 1, no violation if 0. D 2 CH2 LO Violation of DATALOW limit on Channel 2 if this bit set to 1, no violation if 0. D 3 CH2 HI Violation of DATAHIGH limit on Chan nel 2 if this bit set to 1, no violation if 0. D 4 CH3 LO Violation of DATALOW limit on Channel 3 if this bit set to 1, no violation if 0. D 5 CH3 HI Violation of DATAHIGH limit on Chan nel 3 if this bit set to 1, no violation if 0. Violation of DATALOW limit on Channel 4 if this bit set to 1, no violation if 0. D 6 CH4 LO D 7 CH4 HI Table XIa. Alert Status Register D7 D6 D5 D4 D3 D2 D1 D0 CH4HI CH4 LO CH3HI CH3 LO CH2HI CH2 LO CH1HI CH1 LO REV. PrF –19– Violation of DATAHIGH limit on Chan nel 4 if this bit set to 1, no violation if 0. PRELIMINARY TECHNICAL DATA AD7994/AD7993 CYCLE TIMER REGISTER The Cycle Timer Register is a 8-bit read/write register, which stores the conversion interval value for the Automatic Cycle mode of the AD7994/AD7993, see Modes of Operation section. The five MSBs of the Cycle Timer Register are unused and should contain 0’s at all times. On power up, the Cycle Timer Register will contain all 0s, thus disabling the Automatic Cycle operation of the AD7994/AD7993. To enable the Automatic Cycle Mode the user must write to the Cycle Timer Register, selecting the required conversion interval. Table XIIa shows the structure of the Cycle Timer register while Table XIIb shows how the bits in this register are decoded to provide various automatic sampling intervals. Table XIIa. D7 D6 D5 Cycle Timer Register D4 D3 D2 Sample Bit Trial 0 Dealy Delay 0 0 Cyc Cyc Cyc Bit2 Bit1 Bit0 0* 0* 0* 0* 0* 0* D1 0* D0 0* * Default settings on Power-up Table XIIb. D2 D1 D0 0 0 0 0 0 1 0 1 1 0 1 0 1 1 1 1 TCONVERT ADC. Cycle Timer Intervals Conversion Interval (typ) 0 Mode not selected 1 T CONVERT x 32 0 T CONVERT x 64 1 T CONVERT x 128 0 T CONVERT x 256 1 T CONVERT x 512 0 T CONVERT x 1024 1 T CONVERT x 2048 is equivalent to the conversion time of the –20– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 high transition when the clock is high may be interpreted as a STOP signal. SERIAL INTERFACE Control of the AD7994/AD7993 is carried out via the I2C-compatible serial bus. The AD7994/AD7993 is connected to this bus as a slave device, under the control of a master device, e.g. the processor. 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 9th 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, then high during the 10th clock pulse to assert a STOP condition. SERIAL BUS ADDRESS Like all I2C-compatible devices, the AD7994/AD7993 has a 7-bit serial address. The three MSBs of this address for the AD7994/AD7993 are set to 010. The AD7994/ AD7993 comes in two versions, the AD7994-0/AD7993-0 and AD7994-1/AD7993-1. The two versions have three different I2C addresses available which are selected by either tying the Address Select pin, AS, to GND, to VDD or letting the pin float (see Table I). By giving different addresses for the two versions, up to five AD7994/ AD7993 devices can be connected to a single serial bus, or the addresses can be set to avoid conflicts with other devices on the bus. See I2C Address Selection table. Any number of bytes of data may 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. WRITING TO THE AD7994/AD7993 Depending on the register being written to, there are two different writes for the AD7994/AD7993. The serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a START condition, defined as a high to low transition on the serial data line SDA whilst 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 8 bits, consisting of a 7-bit address (MSB first) plus a 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. Writing to the Address Pointer Register for a Subsequent Read In order to read from a particular register, the Address Pointer register must first 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 10. 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 maybe subsequently performed to read the register of interest. 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 whilst the selected device waits for data to be read from or written to it. If the R/W bit is a 0 then the master will write to the slave device. If the R/W bit is a 1 the master will read from the slave device. Writing a Single Byte of Data to the Alert Status Register or Cycle Register The Configuration Register and Cycle Register are both 8-bit registers, so only one byte of data can be written to each. Writing a single byte of data to one of these registers consists of the serial bus write address, the chosen 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 11. 2. Data is sent over the serial bus in sequences of 9 clock pulses, 8 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, as a low to 1 Writing two Bytes of Data to a Limit Register, Hysteresis Register or Configuration register. Each of the four Limit Registers are 12-bit registers, so two bytes of data are required to write a value to any one of them. Writing two bytes of data to one of these registers consists of the serial bus write address, the chosen Limit Register address written to the Address Pointer Register, followed by two data bytes written to the selected data register. This is illustrated in Figure 12. 9 1 9 SCL SDA 0 1 0 A3 A2 A1 START BY MASTER A0 C4 R/9 C3 C2 C1 P3 P2 Figure 10. Writing to the Address Pointer Register to select a register for a subsequent Read operation –21– P0 ACK. BY AD7994/3 FRAME 2 ADDRESS POINTER REGISTER BYTE FRAME 1 SERIAL BUS ADDRESS BYTE REV. PrF P1 ACK. BY AD7994/3 STOP BY MASTER PRELIMINARY TECHNICAL DATA AD7994/AD7993 1 9 1 9 SCL 0 SDA 1 0 A3 A2 A1 A0 C4 R/9 START BY MASTER C3 C2 P3 C1 P2 P1 P0 ACK. BY AD7994/3 ACK. BY AD7994/3 FRAME 2 ADDRESS POINTER REGISTER BYTE FRAME 1 SERIAL BUS ADDRESS BYTE 9 1 9 SCL (CONTINUED) SDA (CONTINUED) D7 D6 D5 D3 D4 D2 D1 D0 ACK. BY AD7994/3 STOP BY MASTER FRAME 3 DATA BYTE Figure 11. Single Byte Write Sequence 1 9 1 9 SCL 0 SDA 1 0 A3 A2 A1 A0 C4 R/9 START BY MASTER C3 C1 P3 P2 P1 P0 ACK. BY AD7994/3 ACK. BY AD7994/3 FRAME 2 ADDRESS POINTER REGISTER BYTE FRAME 1 SERIAL BUS ADDRESS BYTE 9 C2 1 9 1 9 SCL (CONTINUED) SDA (CONTINUED) 0 0 0 D11 0 D10 D9 D8 D7 ACK. BY AD7994/3 MOST SIGNIFICANT DATA BYTE D6 D5 D4 D3 STOP BY MASTER D2 D1/0 D0/0 ACK. BY AD7994/3 STOP BY MASTER LEAST SIGNIFICANT DATA BYTE Figure 12. Two Byte Write Sequence If the master is write addressing the AD7994/AD7993 and wishes to write to more than one register, then after the first write operation has completed for the first data register in the next byte they can simply write to the address pointer byte to select the next data register for a write operation. This eliminates the need to re-address the device in order to write to another data register. READING DATA FROM THE AD7994/AD7993 Reading data from the AD7994/AD7993 is a one or two byte operation. Reading back the contents of the Configuration Register, Alert Status Register or the Cycle Timer Register is a single byte read operation as shown in Figure 13. This assumes the particular register address has previously been set up by a single byte write operation to the Address Pointer Register, Figure 10. Once the register address has been set up, any number of reads can subsequently be performed from that particular register without having to write to the Address Pointer Register again. If a read from a different register is required, then the relevant register address will have to be written to the Address Pointer Register and again any number of reads from this register may then be performed. Reading data from the Conversion Result Register, DATA HIGH Registers, DATALOW Registers or Hysteresis Registers is a two byte operation as shown in Figure 14. The same rules apply for a two byte read as a single byte read. –22– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 1 9 1 9 SCL SDA 0 1 0 A3 A2 A1 A0 D7 R/9 START BY MASTER D6 D5 D4 D3 D2 D1 D0 ACK. BY AD7994/3 NO ACK. BY MASTER STOP BY MASTER FRAME 2 SINGLE DATA BYTE FROM AD7994/3 FRAME 1 SERIAL BUS ADDRESS BYTE Figure 13. Reading a single byte of data from a selected register 1 9 1 9 SCL SDA 0 1 0 A3 A2 A1 A0 Alert_ Flag R/9 START BY MASTER 0 D11 ACK. BY AD7994/3 D10 D9 D8 ACK. BY MASTER CH ID1 CH ID0 FRAME 1 SERIAL BUS ADDRESS BYTE 1 FRAME 2 MOST SIGNIFICANT DATA BYTE FROM AD7994/3 9 SCL (CONTINUED) SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1/0 D0/0 NO ACK. BY MASTER STOP BY MASTER FRAME 3 LEAST SIGNIFICANT DATA BYTE FROM AD7994/3 Figure 14. Reading two bytes of data from the Conversion Result Register ALERT/BUSY PIN device will win communication rights via standard I2C arbitration during the slave address transfer. The ALERT/BUSY may be configured as an Alert or Busy ouput as shown in Table VI. The ALERT output becomes active when the value in the Conversion Result Register exceeds the value in the DATAHIGH Register or falls below the value in the DATALOW Register . It is reset when a write operation to the Configuration register sets D1 to a 1, or when the conversion result returns N LSBs below or above the value stored in the DATA HIGH Register or DATALOW Register respectively. N is the value in the Hysteresis register. (See Limit Registers section) SMBus ALERT The AD7994/AD7993 ALERT output is an SMBus interrupt line for devices that want to trade their ability to master for an extra pin. The AD7994/AD7993 is a slave only device and uses the SMBus ALERT to signal the host device that it wants to talk. The SMBus ALERT on the AD7994/AD7993 is used as an out of conversion range indicator (a limit violation indicator). The ALERT output requires an external pull-up resistor. This can be connected to a voltage different from VDD provided the maximum voltage rating of the ALERT output pin is not exceeded. The value of the pull-up resistor depends on the application, but should be as large as possible to avoid excessive sink currents at the ALERT output. The ALERT pin has an open-drain configuration which allows the ALERT outputs of several AD7994/AD7993 devices to be wired-AND together when the ALERT pin is active low. D0 of the Configuration Register is used to set the active polarity of the ALERT output. The powerup default is active low. The ALERT function can be disabled or enabled by setting D2 of the Configuration Register to 1 or 0 respectively. The host device can process the ALERT interrupt and simultaneously access all SMBus ALERT devices through the alert response address. Only the device which pulled the ALERT low will acknowledge the ARA (Alert Response Address). If more than one device pulls the ALERT pin low, the highest priority (lowest address) REV. PrF –23– PRELIMINARY TECHNICAL DATA AD7994/AD7993 ure 15. The master must then issue a repeated start followed by the device Address with a R/W bit. The selected device will then acknowledge its address. Placing the AD7994-1/AD7993-1 into High-speed Mode. Hs-Mode communication commences after the master addresses all devices connected to the bus with the Master code, 00001XXX, to indicate that a High-Speed Mode transfer is to begin. No device connected to the bus is allowed to Acknowledge the High-Speed Master code, therefore the code is followed by a not-Acknowledge, Fig- All devices continue to operate in Hs-Mode until such a time as the master issues a STOP condition. When the STOP condition is issued the devices all return to F/S Mode. HIGH-SPEED MODE FAST MODE 1 9 1 9 SCL 0 SDA 0 0 0 1 X X X 0 NACK. START BY MASTER 1 0 A3 A2 A1 A0 Sr ACK. BY AD7994/3 HS-MODE MASTER CODE SERIAL BUS ADDRESS BYTE Figure 15. Placing the part into Hs Mode MODES OF OPERATION is complete, approximately 2 us later, the part will return to shutdown (see point C Figure 16) and remain so until the next rising edge of CONVST. The master can then read address the ADC to obtain the conversion result. The address point register must be pointing to the conversion result register in order to read back the conversion result. When supplies are first applied to the AD7994/AD7993, the ADC powers up in shutdown mode and will normally remain in this shutdown state while not converting. There are three different methods of initiating a conversion on the AD7994/AD7993. If the CONVST pulse does not remain high for more than 1 µs, then the falling edge of CONVST will still initiate a conversion but the result will be invalid as the AD7994/AD7993 will not be fully powered up when the conversion takes place. The CONVST pin should not be pulsed when reading from or writing to the serial port. Mode 1 - Using CONVST Pin. A conversion can be initiated on the AD7994/AD7993 by pulsing the CONVST signal. The conversion clock for the part is internally generated so no external clock is required, except when reading from, or writing to the serial port. On the rising edge of CONVST the AD7994/ AD7993 will begin to power up, see point A on Figure 16. The power up time from shutdown mode for the AD7994/AD7993 is approximately 1 us, the CONVST signal must remain high for 1 µs for the part to power up fully. Then CONVST can be brought low after this time. The falling edge of the CONVST signal places the track and hold into hold mode and a conversion is also initiated at this point, see point B Figure 16. When the conversion A B The Cycle Timer Register and bits C4 - C1 in the Address Pointer Register should contain all 0’s to operate the AD7994/AD7993 in this mode. The CONVST pin should be tied low for all other Modes of operation. To select an Analog Input Channel for conversion in this mode, the user must write to the Configuration Register and select the corresponding channel for conversion. To set up a sequence of channels to be converted on with each CONVST pulse, set the corresponding channel bits in the Configuration register, see Table V. C tPOWER-UP CONVST tCONVERT 9 1 1 9 9 SCL SDA S 7-BIT ADDRESS R A FIRST DATA BYTE (MSBs) A SECOND DATA BYTE (LSBs) A P Figure 16. Mode 1 Operation –24– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 see point A Figure 17. Table XIII shows the channel selection in this mode via the command bits, C4 to C1 in the Address Pointer Register. The wake-up and conversion time together should take approximately 3µs. Following this, the AD7994/AD7993 must be addressed again to tell it that a read operation is required. The read then takes place from the Conversion Result register. This read will access the result from the conversion selected via the command bits. If the Command bits C2, C1 were set to 1,1, then a four byte read would be necessary. The first read accesses the data from the conversion on VIN1. While this read takes place, a conversion occurs on VIN2. The second read will access this data from VIN2. Figure 18 illustrates how this mode operates. Mode 2 This mode allows a conversion to be automatically initiated anytime a read operation occurs. In order to use this mode the command bits C4 - C1 in the Address Pointer Byte shown in Table II must be programmed. To select a particular Analog input for conversion in this mode, then the user must set the corresponding channel command bit to 1 in the Address Pointer Byte, see Table XIII. When all four command bits are 0 then this mode is not in use. A sequence can also be set up for this mode, if more than one of the command bit in the Address Pointer Byte are set. The ADC will start converting on the lowest channel in the sequence and then the next lowest until all the channels in the sequence have been converted on. Figure 13 illustrates a two byte read operation from the Conversion Result Register. This operation would normally be preceded by a write to the Address Pointer Register so that the following read will access the desired register, in this case the Conversion Result Register Figure 10. When the contents of the Address Pointer Register are being loaded, if the command bits C4 to C1 are set then the AD7994/AD7993 will begin to power up and convert upon the selected channel(s), power-up will begin on the fifth SCL falling edge of the Address Point Byte, When operating the AD7994-1/AD7993-1 in Mode2 with Hs-Mode, 3.4 MHz SCL, the conversion may not be complete before the master tries to read the conversion result, if this is the case the AD7994-1/AD7993-1 will hold the SCL line low after the read address during the ACK clock, until the conversion is complete. When the conversion is complete the AD7994-1/AD7993-1 will release the SCL line and the master can then read the conversion result. Table XIII Address Pointer Byte C4 C3 C2 C1 P3 P2 P1 P0 Analog Input Channel 0 0 0 0 0 0 0 0 Mode 2 not selected 0 0 0 1 0 0 0 0 Mode 2 Convert on VIN1 0 0 1 0 0 0 0 0 Mode 2 Convert on VIN2 0 0 1 1 0 0 0 0 Mode 2 Sequence between VIN1 and VIN2 0 1 0 0 0 0 0 0 Mode 2 Convert on VIN3 0 1 0 1 0 0 0 0 Mode 2 Sequence between VIN1 and VIN3 0 1 1 0 0 0 0 0 Mode 2 Sequence between VIN2 and VIN3 0 1 1 1 0 0 0 0 Mode 2 Sequence between VIN1, VIN2 and VIN3 1 0 0 0 0 0 0 0 Mode 2 Convert on VIN4 1 0 0 1 0 0 0 0 Mode 2 Sequence between VIN1 and VIN4 1 0 1 0 0 0 0 0 Mode 2 Sequence between VIN2 and VIN4 1 0 1 1 0 0 0 0 Mode 2 Sequence between VIN1, VIN2 and VIN4 1 1 0 0 0 0 0 0 Mode 2 Sequence between VIN3 and VIN4 1 1 0 1 0 0 0 0 Mode 2 Sequence between VIN1, VIN3 and VIN4 1 1 1 0 0 0 0 0 Mode 2 Sequence between VIN2, VIN3 and VIN4 1 1 1 1 0 0 0 0 Mode 2 Sequence between VIN1, VIN2, VIN3 and VIN4 With the pointer bits set to all 0’s then the next read will access the results of the conversion Result Register. REV. PrF –25– PRELIMINARY TECHNICAL DATA AD7994/AD7993 1 8 9 1 W A COMMAND/ADDRESS POINT BYTE A A 9 SCL SDA S 7-BIT ADDRESS ACK BY AD7994/3 ACK BY AD7994/3 1 9 9 9 1 SCL SDA Sr 7-BIT ADDRESS R A A FIRST DATA BYTE (MSBs) ACK BY AD7994/3R A SECOND DATA BYTE (LSBs) ACK BY MASTER Sr/ P NACK BY MASTER Figure 17. Mode 2 Operation 8 1 9 1 A 9 SCL SDA 7-BIT ADDRESS S W A COMMAND/ADDRESS POINT BYTE A ACK BY AD7994/3 ACK BY AD7994/3 1 9 9 9 9 9 1 SCL SDA Sr 7-BIT ADDRESS R A ACK BY AD7994/3 FIRST DATA BYTE (MSBs) A SECOND DATA BYTE (LSBs) ACK BY MASTER A ACK BY MASTER RESULT FROM CH1 FIRST DATA BYTE (MSBs) A SECOND DATA BYTE (LSBs) A/A ACK BY MASTER RESULT FROM CH2 Figure 18. Mode 2 Sequence Operation Mode 3 - Automatic Cycle Mode An automatic conversion cycle can be selected and enabled by writing a value to the Cycle Timer Register. A conversion cycle interval can be set up on the AD7994/AD7993 by programming the relevant bits in the 3-bit Cycle Timer Register as decoded in Table XIIb. When the Cycle Timer register is programmed with any configuration other than all 0’s, a conversion will take place every X ms, depending on the configuration of these bits in the Cycle Timer Register. There are 7 different cycle time intervals to choose from as shown in Table XIIb. Once the conversion has taken place the part powers down again until the next conversion occurs. To exit this mode of operation the user must program the Cycle Timer Register to contain all 0’s. For cycle interval options see Table XIIb Cycle Timer Intervals. To select a channel(s) for operation in the cycle mode set the corresponding channel bit(s), D7 to D4, of the Configuration Register. If more than one channel bit is set in the Configuration register the ADC will automatically cycle through the Channel sequence, starting with the lowest channel and working its way up through the sequence. Once the sequence is complete the ADC will start converting on the lowest channel again, continuing to loop through the sequence until the Cycle timer register contents are set to all 0’s. This mode is useful for monitoring signals, e.g. battery voltage, temperature etc, interrupting only when the limits are violated. –26– REV. PrF PRELIMINARY TECHNICAL DATA AD7994/AD7993 It is recommended that no I2C Bus activity occurs when a conversion is taking place. However if this is not possible, e.g. when operating in Mode 2 or Mode 3, then in order to maintain the performance of the ADC, Bits D7 and D6 in the Cycle Timer Register are used to delay critical sample intervals and bit trials from occurring while there is activity on the I2C Bus. This will result in a quiet period for each bit decision. In certain cases where there is excessive activity on the interface lines this may have the effect of increasing the overall Conversion time. However if bit trial delays extend longer than 1 µs the conversion will terminate. When bits D7 and D6 are both 0, the bit trial and sample interval delaying mechanism will be implemented. The default setting of D7 and D6 is 0. To turn off both set D7 and D6 to 1. Cycle Timer Register D7 D6 D4 D3 D2 Sample Bit Trial 0 Dealy Delay 0 0 Cyc Cyc Cyc Bit2 Bit1 Bit0 0* 0* 0* 0* 0* D5 0* D1 D0 0* 0* *Default settings at Power-up OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 16-Lead TSSOP (RU-16) 0.201 (5.10) 0.193 (4.90) 0.256 (6.50) 1 0.246 (6.25) 9 0.169 (4.30) 0.177 (4.50) 16 8 0.006 (0.15) PIN 1 0.002 (0.05) SEATING PLANE REV. PrF 0.0433 (1.10) MAX 0.0256 (0.65) BSC 0.0118 (0.30) 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090) –27– 8° 0° 0.028 (0.70) 0.020 (0.50)