Digital Power Monitor with Convert Pin and ALERTB Output ADM1191 FEATURES Power monitoring/power budgeting Central office equipment Telecommunications and data communications equipment PCs/servers GENERAL DESCRIPTION The ADM1191 is an integrated current sense amplifier that offers digital current and voltage monitoring via an on-chip 12-bit analog-to-digital converter (ADC), communicated through an I2C® interface. An internal current sense amplifier measures voltage across the sense resistor in the power path via the VCC pin and the SENSE pin. A 12-bit ADC can measure the current seen in the sense resistor, as well as the supply voltage on the VCC pin. An industry-standard I2C interface allows a controller to read current and voltage data from the ADC. Measurements can be initiated by an I2C command or via the convert (CONV) pin. The CONV pin is especially useful for synchronizing reads on multiple ADM1191 devices. Alternatively, the ADC can run continuously, and the user can read the latest conversion data whenever it is required. Up to 16 unique I2C addresses can be created, depending on the way the A0 pin and the A1 pin are connected. CONV ADM1191 V VCC I A SDA 0 I2 C 12-BIT ADC SCL A1 1 SENSE MUX CURRENT SENSE AMPLIFIER A0 ALERT ALERTB SETV COMPARATOR 05804-001 APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GND Figure 1. 3.15V TO 26V RSENSE VCC SENSE ALERTB CONTROLLER INTERRUPT ADM1191 P = VI SDA SCL SETV CONV GND SDA SCL CONV A1 A0 05804-002 Powered from 3.15 V to 26 V Precision current sense amplifier Precision voltage input 12-bit ADC for current and voltage readback Convert (CONV) pin for commanding an ADC read SETV input for setting overcurrent alert threshold ALERTB output provides an overcurrent interrupt I2C fast mode-compliant interface (400 kHz maximum) 2 address pins allow 16 devices on the same bus 10-lead MSOP Figure 2. Applications Diagram The ALERTB output can be used as a flag to warn a microcontroller or field programmable gate array (FPGA) of an overcurrent condition. ALERTB outputs of multiple ADM1191 devices can be tied together and used as a combined alert. The ADM1191 is packaged in a 10-lead MSOP. A SETV pin is also included. A voltage applied to this pin is internally compared with the output voltage on the current sense amplifier. The output of the SETV comparator asserts when the current sense amplifier output exceeds the SETV voltage. When this event occurs, the ALERTB output asserts. Rev. B 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: 781.461.3113 ©2006–2008 Analog Devices, Inc. All rights reserved. ADM1191 TABLE OF CONTENTS Features .............................................................................................. 1 Identifying the ADM1191 on the I2C Bus..................................9 Applications....................................................................................... 1 General I2C Timing.......................................................................9 General Description ......................................................................... 1 Write and Read Operations........................................................... 11 Functional Block Diagram .............................................................. 1 Quick Command........................................................................ 11 Revision History ............................................................................... 2 Write Command Byte ................................................................ 11 Specifications..................................................................................... 3 Write Extended Command Byte .............................................. 12 Absolute Maximum Ratings............................................................ 5 Read Voltage and/or Current Data Bytes................................ 13 Thermal Characteristics .............................................................. 5 Applications Information .............................................................. 15 ESD Caution.................................................................................. 5 ALERTB Output ......................................................................... 15 Pin Configuration and Function Descriptions............................. 6 SETV Pin ..................................................................................... 15 Typical Performance Characteristics ............................................. 7 Kelvin Sense Resistor Connection ........................................... 15 Voltage and Current Readback ....................................................... 9 Outline Dimensions ....................................................................... 16 Serial Bus Interface....................................................................... 9 Ordering Guide .......................................................................... 16 REVISION HISTORY 2/08—Rev. A to Rev. B 4/07—Rev. 0 to Rev. A Changed VVCC to VCC Throughout ................................................. 3 Added ADC Conversion Time Parameter .................................... 3 Changes to Input Current for 00 Decode, IADRLOW, Parameter ... 4 Changes to Input Current for 11 Decode, IADRHIGH, Parameter... 4 Added Endnote 2 .............................................................................. 4 Changes to Figure 6.......................................................................... 7 Changes to Identifying the ADM1191 on the I2C Bus Section.........9 Changes to General I2C Timing Section, Step 3........................... 9 Changes to Table 5............................................................................ 9 Changes to Figure 16 and Figure 17............................................. 10 Changes to Quick Command Section ......................................... 11 Changes to Figure 19...................................................................... 11 Changes to Table 7.......................................................................... 11 Changes to Write Extended Command Byte Section................ 12 Changes to Figure 21...................................................................... 12 Changes to Table 9 and Table 11................................................... 12 Changes to Converting ADC Codes to Voltage and Current Readings Section......................................................... 13 Changes to Figure 25...................................................................... 15 Change to SETV Pin Section ........................................................ 15 Changes to Table 1.............................................................................3 Changes to Table 5.............................................................................9 Changes to Figure 16 and Figure 17............................................. 10 Changes to Figure 21...................................................................... 12 Changes to Figure 23 and Figure 24............................................. 13 Added Applications Information Heading ................................. 15 9/06—Revision 0: Initial Version Rev. B | Page 2 of 16 ADM1191 SPECIFICATIONS VCC = 3.15 V to 26 V, TA = −40°C to +85°C, typical values at TA = 25°C, unless otherwise noted. Table 1. Parameter VCC PIN Operating Voltage Range, VCC Supply Current, ICC Undervoltage Lockout, VUVLO Undervoltage Lockout Hysteresis, VUVLOHYST CONV PIN Input Current, ICONV Logic Low Threshold, VCONVL Logic High Threshold, VCONVH MONITORING ACCURACY 1 Current Sense Absolute Accuracy 0°C to +70°C 0°C to +85°C −40°C to +85°C Min Typ 3.15 1.7 2.8 80 −2 Max Unit 26 2 V mA V mV Conditions VCC rising +2 1.2 μA V V −1.45 +1.45 % VSENSE = 75 mV −1.8 +1.8 % VSENSE = 50 mV −2.8 +2.8 % VSENSE = 25 mV −5.7 +5.7 % VSENSE = 12.5 mV −1.5 +1.5 % VSENSE = 75 mV 1.4 −1.8 +1.8 % VSENSE = 50 mV −2.95 +2.95 % VSENSE = 25 mV −6.1 +6.1 % VSENSE = 12.5 mV −1.95 +1.95 % VSENSE = 75 mV −2.45 +2.45 % VSENSE = 50 mV −3.85 +3.85 % VSENSE = 25 mV −6.7 +6.7 % VSENSE = 12.5 mV 2 VSENSE for ADC Full Scale Voltage Sense Accuracy 105.84 mV 0°C to +70°C −0.85 +0.85 % VCC = 3.0 V to 5.5 V (low range) 0°C to +85°C −0.9 −0.85 +0.9 +0.85 % % VCC = 10.8 V to 16.5 V (high range) VCC = 3.0 V to 5.5 V (low range) −40°C to +85°C −0.9 −0.9 +0.9 +0.9 % % VCC = 10.8 V to 16.5 V (high range) VCC = 3.0 V to 5.5 V (low range) −1.15 +1.15 % VCC = 10.8 V to 16.5 V (high range) VCC for ADC Full Scale 3 Low Range (VRANGE = 1) High Range (VRANGE = 0) ADC Conversion Time 4 SENSE PIN Input Current, ISENSE SETV PIN Overcurrent Trip Threshold Overcurrent Trip Gain, VSETV/(VCC − VSENSE) Input Current, ISETVLEAK ALERTB PIN Output Low Voltage, VALERTOL Input Current, IALERT 6.65 26.52 150 −1 98 49.5 100 50 18 −1 0.05 1 −1 Rev. B | Page 3 of 16 V V μs +1 μA VSENSE = VCC 102 50.5 mV mV +1 μA VSETV = 1.8 V VSETV = 0.9 V VSETV = 0.9 V to 1.9 V VSETV = 0.9 V to 1.9 V 0.1 1.5 +1 V mA μA IALERT = −100 μA IALERT = −2 mA VALERT = VCC; ALERTB not asserted ADM1191 Parameter A0 PIN, A1 PIN Set Address to 00, VADRLOWV Set Address to 01, RADRLOWZ Min Typ Max Unit Conditions 0 80 120 0.8 160 V kΩ +0.3 μA 5.5 V μA Low state Resistor to ground state, load pin with specified resistance for 01 decode Open state, maximum load allowed on the A0 pin or A1 pin for 10 decode High state VADR = 0 V to 0.8 V 6 μA VADR = 2.0 V to 5.5 V 0.3 VBUS Set Address to 10, IADRHIGHZ −0.3 Set Address to 11, VADRHIGHV Input Current for 00 Decode, IADRLOW 2 −40 Input Current for 11 Decode, IADRHIGH I2C TIMING Low Level Input Voltage, VIL High Level Input Voltage, VIH Low Level Output Voltage on SDA, VOL Output Fall Time on SDA from VIHMIN to VILMAX Maximum Width of Spikes Suppressed by Input Filtering on SDA and SCL Pins Input Current, II, on SDA/SCL When Not Driving a Logic Low Output Input Capacitance on SDA/SCL SCL Clock Frequency, fSCL Low Period of the SCL Clock High Period of the SCL Clock Setup Time for Repeated Start Condition, tSU;STA SDA Output Data Hold Time, tHD;DAT Setup Time for a Stop Condition, tSU;STO Bus Free Time Between a Stop and a Start Condition, tBUF Capacitive Load for Each Bus Line −25 3 20 + 0.1 CBUS 50 0.4 250 250 V V V ns ns −10 +10 μA 0.7 VBUS 5 400 600 1300 600 100 600 1300 900 400 1 IOL = 3 mA CBUS = bus capacitance from SDA to GND pF kHz ns ns ns ns ns ns pF Monitoring accuracy is a measure of the error in a code that is read back for a particular voltage/current. This is a combination of amplifier error, reference error, ADC error, and error in ADC full-scale code conversion factor. 2 This is an absolute value to be used when converting ADC codes to current readings; any inaccuracy in this value is factored into absolute current accuracy values (see the specifications for the Current Sense Absolute Accuracy parameter). 3 These are absolute values to be used when converting ADC codes to voltage readings; any inaccuracy in these values is factored into voltage accuracy values (see the specifications for the Voltage Sense Accuracy parameter). 4 Time between the receipt of the command byte and the actual ADC result being placed in the register. Rev. B | Page 4 of 16 ADM1191 ABSOLUTE MAXIMUM RATINGS THERMAL CHARACTERISTICS Table 2. Parameter VCC Pin SENSE Pin CONV Pin SETV Pin ALERTB Pin SDA Pin, SCL Pin A0 Pin, A1 Pin Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec) Junction Temperature θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Rating 30 V 30 V −0.3 V to +6 V 30 V 30 V −0.3 V to +6 V −0.3 V to +6 V −65°C to +125°C −40°C to +85°C 300°C 150°C Table 3. Thermal Resistance Package Type 10-Lead MSOP ESD CAUTION 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. Rev. B | Page 5 of 16 θJA 137.5 Unit °C/W ADM1191 VCC 1 10 ALERTB SENSE 2 ADM1191 9 A1 CONV 3 TOP VIEW (Not to Scale) 8 A0 7 SDA 6 SCL GND 4 SETV 5 05804-003 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 3. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 Mnemonic VCC 2 SENSE 3 CONV 4 5 GND SETV 6 7 8 SCL SDA A0 9 A1 10 ALERTB Description Positive Supply Input Pin. The operating supply voltage range is from 3.15 V to 26 V. An undervoltage lockout (UVLO) circuit resets the ADM1191 when a low supply voltage is detected. Current Sense Input Pin. A sense resistor between the VCC pin and the SENSE pin generates a voltage across a sense resistor. This voltage is proportional to the load current. A current sense amplifier amplifies this voltage before it is digitized by the ADC. Convert Start Pin. A high level on this pin enables an ADC conversion. The state of an internal control register, which is set through the I2C interface, configures the part to convert current only, voltage only, or both channels when the convert pin is asserted. Chip Ground Pin. Input Pin. The voltage driven onto this pin is compared with the output of the internal current sense amplifier. The lower the voltage on the SETV, the lower the current level that causes the ALERTB output to assert. I2C Clock Pin. Open-drain input; requires an external resistive pull-up. I2C Data I/O Pin. Open-drain input/output; requires an external resistive pull-up. I2C Address Pin. This pin can be tied low, tied high, left floating, or tied low through a resistor. Sixteen I2C address options are available, depending on the external configuration of the A0 pin and the A1 pin. I2C Address Pin. This pin can be tied low, tied high, left floating, or tied low through a resistor. Sixteen I2C address options are available, depending on the external configuration of the A0 pin and the A1 pin. Alert Output Pin. Active low, open-drain configuration. This pin asserts low when an overcurrent condition is present. The level at which an overcurrent condition is detected depends on the voltage on the SETV pin. Rev. B | Page 6 of 16 ADM1191 TYPICAL PERFORMANCE CHARACTERISTICS 1000 2.0 900 HITS PER CODE (1000 READS) 1.8 1.6 ICC (mA) 1.4 1.2 1.0 0.8 0.6 800 700 600 500 400 300 200 0.4 100 0 0 4 8 12 16 20 24 28 VCC (V) 2046 05804-021 0 Figure 4. Supply Current vs. Supply Voltage 2047 2048 2049 2050 CODE 05804-060 0.2 Figure 7. ADC Noise with Current Channel, Midcode Input, and 1000 Reads 1000 2.0 900 HITS PER CODE (1000 READS) 1.8 1.6 ICC (mA) 1.4 1.2 1.0 0.8 0.6 800 700 600 500 400 300 200 0.4 100 0 –20 0 20 40 60 80 TEMPERATURE (°C) 01 DECODE 781 782 783 CODE 1000 10 DECODE 11 DECODE HITS PER CODE (1000 READS) 900 800 700 600 500 400 300 200 0 –30 –25 –20 –15 –10 –5 0 5 IA0/IA1 (µA) Figure 6. Address Pin Voltage vs. Address Pin Current for Four Addressing Options on Each Address Pin 10 3078 3079 3080 CODE 3081 3082 05804-062 100 05804-026 VA0/VA1 (V) 00 DECODE 780 Figure 8. ADC Noise with 14:1 Voltage Channel, 5 V Input, and 1000 Reads Figure 5. Supply Current vs. Temperature 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –35 779 05804-022 0 –40 05804-061 0.2 Figure 9. ADC Noise with 7:1 Voltage Channel, 5 V Input, and 1000 Reads Rev. B | Page 7 of 16 ADM1191 0.60 4 0.55 3 ALERTB OUTPUT LOW (V) 0.50 2 INL (LSB) 1 0 –1 –2 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 –3 500 1000 1500 2000 2500 3000 3500 4000 CODE 0 –40 05804-023 0 –20 0 20 40 60 05804-047 0.05 –4 80 TEMPERATURE (°C) Figure 10. INL for ADC Figure 13. ALERTB Output Low Voltage vs. Temperature @ 1 mA 1.0 4 3 ALERTB OUTPUT LOW (V) 0.8 DNL (LSB) 2 1 0 –1 –2 0.6 0.4 0.2 0 500 1000 1500 2000 2500 3000 3500 4000 CODE 0 05804-024 2 4 6 8 10 12 14 16 18 20 22 24 26 28 VCC (V) Figure 11. DNL for ADC Figure 14. ALERTB Output Low Voltage vs. Supply Voltage @ 1 mA 2.0 100 1.8 90 1.6 ALERTB OUTPUT LOW (V) 80 70 60 50 40 30 1.4 1.2 1.0 0.8 0.6 20 0.4 10 0.2 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 VSETV (V) 05804-046 VLIM (mV) 0 Figure 12. Overcurrent Limit Threshold vs. SETV Pin Voltage 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 ILOAD (mA) Figure 15. ALERTB Output Low Voltage vs. Load Current Rev. B | Page 8 of 16 05804-049 –4 05804-048 –3 ADM1191 VOLTAGE AND CURRENT READBACK The ADM1191 contains the components to allow voltage and current readback over an I2C bus. The voltage output of the current sense amplifier and the voltage on the VCC pin are fed into a 12-bit ADC via a multiplexer. The device can be instructed to convert voltage and/or current at any time during operation by issuing an I2C command or driving the CONV pin high. When all conversions are complete, the voltage and/or current values can be read back with 12-bit accuracy in two or three bytes. 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, and holding it low during the high period of this clock pulse. All other devices on the bus remain idle while the selected device waits for data to be read from it or written to it. If the R/W bit is 0, the master writes to the slave device. If the R/W bit is 1, the master reads from the slave device. SERIAL BUS INTERFACE Control of the ADM1191 is carried out via the serial system management bus (I2C). This interface is compatible with the I2C fast mode (400 kHz maximum). The ADM1191 is connected to this bus as a slave device, under the control of a master device. 2. IDENTIFYING THE ADM1191 ON THE I2C BUS The ADM1191 has a 7-bit serial bus slave address. When the device powers up, it does so with a default serial bus address. The three MSBs of the address are set to 011; the four LSBs are determined by the state of the A0 pin and the A1 pin. There are 16 configurations available on the A0 pin and A1 pin that correspond to 16 I2C addresses for the four LSBs (see Table 5). This scheme allows 16 ADM1191 devices to operate on a single I2C bus. If the operation is a write operation, the first data byte after the slave address is a command byte. This tells the slave device what to expect next. It can be an instruction, such as telling the slave device to expect a block write, or it can be a register address that tells the slave where subsequent data is to be written. GENERAL I2C TIMING Because data can flow in only one direction, as defined by the R/W bit, it is not possible to send a command to a slave device during a read operation. Before performing a read operation, it may be necessary to first execute a write operation to tell the slave what sort of read operation to expect and/or the address from which data is to be read. Figure 16 and Figure 17 show timing diagrams for general write and read operations using the I2C. The I2C specification defines conditions for different types of read and write operations, which are discussed in the Write and Read Operations section. The general I2C protocol operates as follows: 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 a data stream is to 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 slave address (MSB first) plus an R/W bit that determines the direction of the data transfer, that is, whether data is written to or read from the slave device (0 = write, 1 = read). Data is sent over the serial bus in sequences of nine clock pulses: eight bits of data followed by an acknowledge bit from the slave device. Data transitions on the data line must occur during the low period of the clock signal and remain stable during the high period because a low-tohigh transition when the clock is high can be interpreted as a stop signal. 3. When all data bytes are read or written, stop conditions are established. In write mode, the master pulls the data line high during the 10th clock pulse to assert a stop condition. In read mode, the master device releases the SDA line during the SCL low period before the ninth clock pulse, but the slave device does not pull it low. This is known as a no acknowledge. The master then takes the data line low during the SCL low period before the 10th clock pulse and then high during the 10th clock pulse to assert a stop condition. Table 5. Setting I2C Addresses via the A0 Pin and the A1 Pin Base Address 011 A1 Pin State Ground Ground Ground Ground Resistor to ground Resistor to ground Resistor to ground Resistor to ground Floating Floating A0 Pin State Ground Resistor to ground Floating High Ground Resistor to ground Floating High Ground Resistor to ground A1 Pin Logic State 00 00 00 00 01 01 01 01 10 10 Rev. B | Page 9 of 16 A0 Pin Logic State 00 01 10 11 00 01 10 11 00 01 Address in Binary1 0110000X 0110001X 0110010X 0110011X 0110100X 0110101X 0110110X 0110111X 0111000X 0111001X Address in Hex 0x60 0x62 0x64 0x66 0x68 0x6A 0x6C 0x6E 0x70 0x72 ADM1191 Base Address A0 Pin State Floating High Ground Resistor to ground Floating High A1 Pin Logic State 10 10 11 11 11 11 Address in Binary1 0111010X 0111011X 0111100X 0111101X 0111110X 0111111X A0 Pin Logic State 10 11 00 01 10 11 Address in Hex 0x74 0x76 0x78 0x7A 0x7C 0x7E X = don’t care. 9 1 9 1 SCL 0 SDA 1 1 A1A A0A A1B A0B D7 R/W D6 D5 ACKNOWLEDGE BY SLAVE START BY MASTER FRAME 1 SLAVE ADDRESS 1 D4 D2 D3 D0 D1 ACKNOWLEDGE BY SLAVE FRAME 2 COMMAND CODE 1 9 9 SCL (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 ACKNOWLEDGE BY SLAVE FRAME 3 DATA BYTE D3 D2 D1 D0 ACKNOWLEDGE BY STOP BY SLAVE MASTER FRAME N DATA BYTE 05804-004 SDA (CONTINUED) Figure 16. General I2C Write Timing Diagram 9 1 9 1 SCL 0 SDA 1 1 A1A A0A A1B A0B D7 R/W D6 D5 D4 ACKNOWLEDGE BY SLAVE START BY MASTER FRAME 1 SLAVE ADDRESS 1 D2 D3 D0 D1 ACKNOWLEDGE BY MASTER FRAME 2 DATA BYTE 1 9 9 SCL (CONTINUED) D7 D6 D5 D4 D3 FRAME 3 DATA BYTE D2 D1 D0 D7 D6 D5 ACKNOWLEDGE BY MASTER D4 D3 FRAME N DATA BYTE D2 D1 D0 NO ACKNOWLEDGE STOP BY MASTER Figure 17. General I2C Read Timing Diagram tLOW tR tHD;STA tF SCL tHD;STA tSU;STA tHIGH tHD;DAT tSU;DAT tSU;STO SDA tBUF P S S Figure 18. Serial Bus Timing Diagram Rev. B | Page 10 of 16 P 05804-005 SDA (CONTINUED) 05804-006 1 A1 Pin State Floating Floating High High High High ADM1191 WRITE AND READ OPERATIONS WRITE COMMAND BYTE In the write command byte operation, the master device sends a command byte to the slave device, as follows: 1. 2. Table 6. I2C Abbreviations Abbreviation S P R W A N 3. 4. Condition Start Stop Read Write Acknowledge No acknowledge 5. 6. The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the write bit (low). The addressed slave device asserts an acknowledge on SDA. The master sends the command byte. The command byte is identified by an MSB = 0. An MSB = 1 indicates an extended register write (see the Write Extended Command Byte section). The slave asserts an acknowledge on SDA. The master asserts a stop condition on SDA to end the transaction. QUICK COMMAND 1 The quick command operation allows the master to check if the slave is present on the bus, as follows: COMMAND SLAVE S ADDRESS W A A P BYTE 3. 4. The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the write bit (low). The addressed slave device asserts an acknowledge on SDA. The master asserts a stop condition on SDA to end the transaction. 1 2 3 4 5 6 Figure 20. Write Command Byte The seven LSBs of the command byte are used to configure and control the ADM1191. Table 7 provides details of the function of each bit. 3 4 SLAVE S ADDRESS W A P 05804-007 1. 2. 2 05804-008 The I2C specification defines several protocols for different types of read and write operations. The operations used in the ADM1191 are discussed in this section. Table 6 shows the abbreviations used in the command diagrams (see Figure 19 to Figure 24). Figure 19. Quick Command Table 7. Command Byte Operations Bit Default Name C0 0 V_CONT C1 0 V_ONCE C2 0 I_CONT C3 0 I_ONCE C4 0 VRANGE C5 C6 0 0 N/A STATUS_RD Function LSB, set to convert voltage continuously. If readback is attempted before the first conversion is complete, the ADM1191 asserts an acknowledge and returns all 0s in the returned data. Set to convert voltage once. Self-clears. I2C asserts a no acknowledge on attempted reads until the ADC conversion is complete. Set to convert current continuously. If readback is attempted before the first conversion is complete, the ADM1191 asserts an acknowledge and returns all 0s in the returned data. Set to convert current once. Self-clears. I2C asserts a no acknowledge on attempted reads until the ADC conversion is complete. Selects different internal attenuation resistor networks for voltage readback. A 0 in C4 selects a 14:1 voltage divider. A 1 in C4 selects a 7:2 voltage divider. With an ADC full scale of 1.902 V, the voltage at the VCC pin for an ADC full-scale result is 26.52 V for VRANGE = 0 and 6.65 V for VRANGE = 1. Unused. Status Read. When this bit is set, the data byte read back from the ADM1191 is the status byte. It contains the status of the device alerts. See Table 15 for full details of the status byte. Rev. B | Page 11 of 16 ADM1191 WRITE EXTENDED COMMAND BYTE 1. 2. 3. 4. 5. 6. The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the write bit (low). The addressed slave device asserts an acknowledge on SDA. The master sends the register address byte. The MSB of this byte is set to 1 to indicate an extended register write. The two LSBs indicate which of the three extended registers is to be written to (see Table 8). All other bits should be set to 0. The slave asserts an acknowledge on SDA. The master sends the extended command byte (refer to Table 9, Table 10, and Table 11). The slave asserts an acknowledge on SDA. The master asserts a stop condition on SDA to end the transaction. 1 2 3 4 5 6 7 8 EXTENDED REGISTER SLAVE S ADDRESS W A ADDRESS A COMMAND A P BYTE 05804-009 7. 8. In the write extended command byte operation, the master device writes to one of the three extended registers of the slave device, as follows: Figure 21. Write Extended Byte Table 9, Table 10, and Table 11 provide the details of each extended register. Table 8. Extended Register Addresses A6 0 0 0 A5 0 0 0 A4 0 0 0 A3 0 0 0 A2 0 0 0 A1 0 1 1 A0 1 0 1 Extended Register ALERT_EN ALERT_TH CONTROL Table 9. ALERT_EN Register Operations Bit 0 1 Default 0 0 Name EN_ADC_OC1 EN_ADC_OC4 2 1 EN_OC_ALERT 3 4 0 0 EN_OFF_ALERT CLEAR Function LSB, enabled if a single ADC conversion on the I channel exceeds the threshold set in the ALERT_TH register. Enabled if four consecutive ADC conversions on the I channel exceed the threshold set in the ALERT_TH register. Enables the OC_ALERT register. If an overcurrent condition is present, the OC_ALERT register captures and latches this condition. Set this bit high to activate the SWOFF bit (see Table 11). Clears the OFF_ALERT, OC_ALERT, and ADC_ALERT status bits in the status register. The value of these bits may immediately change if the source of the alert is not been cleared and the alert function is not disabled. The CLEAR bit self-clears to 0 after the STATUS register bits have been cleared. Table 10. ALERT_TH Register Operations Bit 7:0 Default FF Function The ALERT_TH register sets the current level at which an alert occurs. Defaults to ADC full scale. The ALERT_TH 8-bit value corresponds to the top eight bits of the current channel data. Table 11. CONTROL Register Operations Bit 0 Default 0 Name SWOFF Function LSB, forces the ALERTB pin to deassert. Can be active only if the EN_OFF_ALERT bit is high (see Table 9). Rev. B | Page 12 of 16 ADM1191 READ VOLTAGE AND/OR CURRENT DATA BYTES 9. The master asserts a no acknowledge on SDA. 10. The master asserts a stop condition on SDA, and the transaction ends. For cases where the master is reading voltage only or current only, two data bytes are read and Step 7 and Step 8 are not required. Voltage and Current Readback 1 The ADM1191 digitizes both voltage and current. Three bytes are read back in the format shown in Table 12. 2 3 B6 V10 B5 V9 B4 V8 B3 V7 B2 V6 B1 V5 B0 V4 I11 I10 I9 I8 I7 I6 I5 I4 V3 V2 V1 V0 I3 I2 I1 I0 Table 13. Voltage Only Readback Format 2 B7 V11 B6 V10 B5 V9 B4 V8 B3 V7 B2 V6 B1 V5 B0 V4 V3 V2 V1 V0 0 0 0 0 The ADM1191 digitizes current only. Two bytes are read back in the format shown in Table 14. 2 B7 I11 B6 I10 B5 I9 B4 I8 B3 I7 B2 I6 B1 I5 B0 I4 I3 I2 I1 I0 0 0 0 0 The following series of events occurs when the master receives three bytes (voltage and current data) from the slave device: 1. 2. 3. 4. 5. 6. 7. 8. 1 2 3 SLAVE R A S ADDRESS 4 5 6 7 8 DATA 1 A DATA 2 N P Converting ADC Codes to Voltage and Current Readings Equation 1 and Equation 2 can be used to convert ADC codes representing voltage and current from the ADM1191 12-bit ADC into actual voltage and current values. Voltage = (VFULLSCALE/4096) × Code (1) where: VFULLSCALE = 6.65 V (7:2 range) or 26.52 V (14:1 range). Code is the ADC voltage code read from the device (Bit V11 to Bit V0). Current = ((IFULLSCALE/4096) × Code)/Sense Resistor (2) Read Status Register Table 14. Current Only Readback Format Contents Current MSBs Current LSBs 9 10 where: IFULLSCALE = 105.84 mV. Code is the ADC current code read from the device (Bit I11 to Bit I0). Current Readback Byte 1 8 Figure 23. Two-Byte Read from ADM1191 The ADM1191 digitizes voltage only. Two bytes are read back in the format shown in Table 13. Contents Voltage MSBs Voltage LSBs 7 Figure 22. Three-Byte Read from ADM1191 Voltage Readback Byte 1 6 05804-011 B7 V11 5 The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the read bit (high). The addressed slave device asserts an acknowledge on SDA. The master receives the first data byte. The master asserts an acknowledge on SDA. The master receives the second data byte. The master asserts an acknowledge on SDA. The master receives the third data byte. A single register of status data can also be read from the ADM1191 as follows: 1. 2. 3. 4. 5. The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the read bit (high). The addressed slave device asserts an acknowledge on SDA. The master receives the status byte. The master asserts an acknowledge on SDA. 1 2 3 SLAVE S ADDRESS R A 4 5 STATUS A BYTE 05804-012 2 Contents Voltage MSBs Current MSBs LSBs 4 SLAVE S ADDRESS R A DATA 1 A DATA 2 A DATA 3 N P Table 12. Voltage and Current Readback Byte 1 3 05804-010 Depending on how the device is configured, ADM1191 can be set up to provide information in three ways after a conversion (or conversions): voltage and current readback, voltage only readback, and current only readback. See the Write Command Byte section for more details. Figure 24. Status Read from ADM1191 Table 15 shows the ADM1191 STATUS registers in detail. Note that Bit 1, Bit 3, and Bit 5 are cleared by writing to Bit 4 (the CLEAR bit) of the ALERT_EN register. Rev. B | Page 13 of 16 ADM1191 Table 15. Status Byte Operations Bit 0 1 2 Name ADC_OC ADC_ALERT OC 3 OC_ALERT 4 5 OFF_STATUS OFF_ALERT Function An ADC-based overcurrent comparison is detected on the last three conversions. An ADC-based overcurrent trip has occurred, causing the alert. Cleared by writing to Bit 4 of the ALERT_EN register. An overcurrent condition is present (that is, the output of the current sense amplifier is greater than the voltage on the SETV input). An overcurrent condition causes the ALERT block to latch a fault, and the ALERTB output asserts. Cleared by writing to Bit 4 of the ALERT_EN register. Set to 1 by writing to the SWOFF bit of the CONTROL register. An alert has been caused by the SWOFF bit. Cleared by writing to Bit 4 of the ALERT_EN register. Rev. B | Page 14 of 16 ADM1191 APPLICATIONS INFORMATION ALERTB OUTPUT The ALERTB output is an open-drain pin with 30 V tolerance. This output can be used as an overcurrent flag by connecting it to the general-purpose logic input of a controller. During normal operation, this output is pulled high (an external pull-up resistor should be used because this is an open-drain pin). When an overcurrent condition occurs, the ADM1191 pulls this output low. VCC SENSE ADM1191 A CURRENT SENSE AMPLIFIER RSENSE APPLIED VOLTAGE SETV ALERTB CONTROLLER P = VI SDA SCL CONV GND COMPARATOR INTERRUPT ADM1191 SETV ALERTB 05804-014 SENSE Figure 26. SETV Operation SDA SCL KELVIN SENSE RESISTOR CONNECTION CONV A1 A0 05804-013 VCC ALERT Figure 25. Using the ALERTB Output as an Interrupt SETV PIN The SETV pin allows the user to adjust the current level that trips the ALERTB output. The output of the current sense amplifier is compared with the voltage driven onto the SETV pin. If the current sense amplifier output is higher than the SETV voltage, the output of the comparator asserts. By driving a different voltage onto the SETV pin, the ADM1191 detects an overcurrent condition at a different current level, with a gain of 18. See Figure 12 for an illustration of this relationship. When using a low value sense resistor for high current measurement, the problem of parasitic series resistance can arise. The lead resistance can be a substantial fraction of the rated resistance, making the total resistance a function of lead length. This problem can be avoided by using a Kelvin sense connection. This type of connection separates the current path through the resistor and the voltage drop across the resistor. Figure 27 shows the correct way to connect the sense resistor between the VCC pin and the SENSE pin of the ADM1191. SENSE RESISTOR CURRENT FLOW FROM SUPPLY CURRENT FLOW TO LOAD KELVIN SENSE TRACES VCC SENSE ADM1191 Figure 27. Kelvin Sense Connections Rev. B | Page 15 of 16 05804-015 3.15V TO 26V ILOAD RSENSE ADM1191 OUTLINE DIMENSIONS 3.10 3.00 2.90 10 3.10 3.00 2.90 1 6 5.15 4.90 4.65 5 PIN 1 0.50 BSC 0.95 0.85 0.75 1.10 MAX 0.15 0.05 0.33 0.17 SEATING PLANE 0.23 0.08 0.80 0.60 0.40 8° 0° COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-187-BA Figure 28. 10-Lead Mini Small Outline Package [MSOP] (RM-10) Dimensions shown in millimeters ORDERING GUIDE Model ADM1191-2ARMZ-R7 1 EVAL-ADM1191EBZ1 1 Temperature Range −40°C to +85°C Package Description 10-Lead MSOP Evaluation Board Package Option RM-10 Branding M5L Z = RoHS Compliant Part. Purchase of licensed I2C components of Analog Devices, Inc., 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. ©2006–2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05804-0-2/08(B) Rev. B | Page 16 of 16