XR :1 Sensor Interface

Transcription

1 6: Sensor Interface General Description The XR9 is a unique sensor interface integrated circuit with an on-board 6: multiplexer, offset correction DC, instrumentation amplifier and voltage reference. The XR9 is designed to integrate multiple bridge sensors with a microcontroller (MCU) or field-programmable gate array (FPG). The integrated offset correction DC provides digital calibration of the variable and in many cases substantial offset voltage generated by the bridge sensors. The DC is controlled by an IC compatible wire serial interface. The serial interface also provides the user with easy controls to the XR9 s many functions such as input and gain selection. n integrated LDO provides a regulated voltage to power the input bridge sensors and is selectable, between V and.65v, via the serial interface for lower voltage compatibility. The LDO current can be sensed and a proportional voltage present at the output of the IC for monitoring the LDO current. The XR9 offers 8 fixed gain settings (from V/V to 76V/V), each with an error of only ±.5%, that are selectable via the IC interface. It also offers less than mv maximum input offset voltage, p maximum input bias current, and p maximum input offset current. The XR9 is designed to operate from.7v to 5V supplies and is specified over the industrial temperature range of -4 C to +85 C. It is offered in a space saving 6mm x 6mm QFN-4 package. It consumes less than 556μ maximum supply current and offers a sleep mode for added power savings. The low power, low input bias current and integrated features make the XR9 well suited for both industrial and consumer applications using bridge sensors. FETURES Integrated features for interfacing multiple bridge sensors with an MCU or FPG: 6: differential mux with IC interface Instrumentation amplifier LDO Offset correction DC with IC interface (±56mV offset correction range - RTI) Eight selectable voltage gains from V/V to 76V/V with only ±.5% gain error mv maximum input offset voltage p maximum input bias current 556μ maximum supply current.7v to 5V analog supply voltage range.8v to 5V digital supply voltage range -4 C to +85 C temperature range 6x6mm QFN-4 PPLICTIONS Bridge sensor interface Pressure & temperature sensors Strain gauge amplifier Industrial process controls Weigh scales Ordering Information - back page Typical pplication BRDG VCC Bridge 6 IN6+ LDO IN6- IN / PG OUT DC µc 6: MUX ±56mV offset trim Bridge IN+ IN- -bit DC IC Control XR9 PG SD SCL 6: Bridge Sensor Interface 4-5 Exar Corporation / 9 exar.com/xr9

2 bsolute Maximum Ratings Stresses beyond the limits listed below may cause permanent damage to the device. Exposure to any bsolute Maximum Rating condition for extended periods may affect device reliability and lifetime. nalog Supply Voltage (V CC)... V to 5.5V Digital Supply Voltage (V DD )... V to 5.5V Digital Input/Output (V DDIO )... V to 5.5V V IN... to V CC Differential Input Voltage (current limit of m)... V CC Operating Conditions nalog Supply Voltage Range....7V to 5.5V Digital Supply Voltage Range...7V to 5.5V Operating Temperature Range...-4 C to 85 C Junction Temperature...5 C Storage Temperature Range C to 5 C Lead Temperature (Soldering, s)...6 C Package Thermal Resistance θ J (QFN-4)... C/W Package thermal resistance (θ J ), JEDEC standard, multi-layer test boards, still air. ESD Protection QFN-4 (HBM)... 4V HBM - ESD Rating Human Body Model. 4-5 Exar Corporation / 9 exar.com/xr9

3 Electrical Characteristics at +.V T = 5 C, V CC =.V, V DD =.8V, R L = kω to.5v; G = 76; unless otherwise noted. Symbol Parameter Conditions Min Typ Max Units DC Performance V IO Input Offset Voltage Input referred - ±. mv d VIO Input Offset Voltage verage Drift μv/ C I B Input Bias Current - 5 p I OS Input Offset Current - p PSRR Power Supply Rejection Ratio V CC =.7V to 5V 6 9 db Gain Gain =. V/V Gain =. V/V Gain = 4 4. V/V Gain = 8 8. V/V Nominal; refer to Gain Register Table (pg. 4) Gain = 5 5. V/V Gain = 99.9 V/V Gain = V/V Gain = V/V GIN ERR Gain Error % Gain Error vs Temperature ± ppm/ C I SVCC V CC Supply Current No load to output; no load to LDO 45 5 μ I SVCCD Disable V CC Supply Current No load to output; no load to LDO μ I SVDD V DD Supply Current No load to output; no load to LDO; IC running 6 μ I STOTL Total Supply Current No load to output; no load to LDO μ I SDTOTL Input Characteristics Total Disable Supply Current No load to output; no load to LDO; LDO DIS 45 μ No load to output; no load to LDO; LDO EN 7 85 μ Input Impedance. Ω pf CMIR Common Mode Input Range.5. to.6.5 V CMRR Common Mode Rejection Ratio Input referred. V cm =.5 to.v db Output Characteristics V OUT Output Voltage Swing R L = kω to.5v..4 to.9. V V OO Output Offset Offset DC ; Gain = V Offset DC LDO Offset DC Range RTI (Referred to Input) ±56 mv Offset Monotonicity 8 Bits Output Voltage.5k load, selectable (LDO bit Low) -6% +6% V.5k load, selectable (LDO bit Hi) -6%.65 +6% V Dropout Voltage V CC =.8V, LDO =.65V, I LOD = m 5 mv Output Current 5 m PSRR Dynamic Performance BW Output referred, V CC = V-5V, LDO =.65V 45 6 db Output referred, V CC =.V-5V, LDO = V 45 6 db Output Current Sense Transimpedance (slope) Output voltage relative to.5v / LDO current G =.8.. V/m Output Current Sense Range (clip) Gain = 8.8 m -db Bandwidth Gain = khz Gain = khz SR Slew Rate V OUT = V pp ; Gain = V/μs 4-5 Exar Corporation / 9 exar.com/xr9

4 Symbol Parameter Conditions Min Typ Max Units f = Hz 75 nv/ Hz e ni Input Voltage Noise - RTI f = Hz 46 nv/ Hz f = khz 5 nv/ Hz i n Input Current Noise f = Hz.6 f/ Hz e npp Peak-to-Peak Noise f =. to Hz μv pp XTLK Crosstalk Channel-to-channel, f = khz 9 db T S Set-up Time (% settling) nalog ready after serial register finished write.5 μs T WKE Wake up Time (% settling) Wake from CK of Sleep_Out command 9.6 μs Digital Characteristics (CMOS) Symbol Parameter Conditions Min Typ Max Units V IH Logic Input Hi.7 x V DD V DD V V IL Logic Input Lo. x V DD V I IH Input Leakage Hi V I = V S μ I IL Input Leakage Lo V I = - μ CLK F Clock Rate.4 MHz I C Bus Timing T = -4 to +85 C, V DD =.8-5V; unless otherwise noted. Symbol Parameter Standard Mode IC-BUS Fast Mode IC-BUS Min Max Min Max f SCL Operating frequency 4 khz T BUF Bus free time between STOP and STRT 4.7. μs T HD;ST STRT condition hold time 4..6 μs T SU;ST STRT condition setup time μs T HD;DT Data hold time μs T VD;CK Data valid acknowledge.6.6 μs T VD;DT SCL LOW to data out valid.6.6 ns T SU;DT Data setup time 5 5 ns T LOW Clock LOW period 4.7. μs T HIGH Clock HIGH period 4..6 μs T F Clock/data fall time ns T R Clock/data rise time ns T SP Pulse width of spikes tolerance.5.5 μs Units 4-5 Exar Corporation 4 / 9 exar.com/xr9

5 IC-BUS Timing Diagram Figure : Timing Diagram 4-5 Exar Corporation 5 / 9 exar.com/xr9

6 Pin Configuration IN+ IN5- IN- 9 IN5+ IN+ 8 IN4- IN- IN+ 4 5 XR9 QFN-4 7 IN4+ 6 IN- IN- 6 5 IN+ IN IN- IN4-8 IN+ IN5+ 9 IN- IN5- IN+ IN6+ IN7+ IN8+ IN9+ IN+ IN6- IN7- IN8- IN9- IN VDD 9 SD 8 SCL 7 DGND 6 VCC 5 OUT 4 GND BRDG IN6- IN6+ Pin ssignments Pin No. Pin Name Description IN+ Positive Input IN- Negative Input IN+ Positive Input 4 IN- Negative Input 5 IN+ Positive Input 6 IN- Negative Input 7 IN4+ Positive Input 4 8 IN4- Negative Input 4 9 IN5+ Positive Input 5 IN5- Negative Input 5 IN6+ Positive Input 6 IN6- Negative Input 6 IN7+ Positive Input 7 4 IN7- Negative Input 7 5 IN8+ Positive Input 8 6 IN8- Negative Input 8 7 IN9+ Positive Input 9 8 IN9- Negative Input 9 9 IN+ Positive Input IN- Negative Input Pin No. Pin Name Description IN+ Positive Input IN- Negative Input IN+ Positive Input 4 IN- Negative Input 5 IN+ Positive Input 6 IN- Negative Input 7 IN4+ Positive Input 4 8 IN4- Negative Input 4 9 IN5+ Positive Input 5 IN5- Negative Input 5 IN6+ Positive Input 6 IN6- Negative Input 6 BRDG BRDG Power Connection ( LDO output ) 4 GND nalog Ground 5 OUT Output 6 VCC nalog Supply 7 DGND Digital Ground 8 SCL Serial Clock Input 9 SD Serial Data Input/Output 4 VDD Digital Supply 4-5 Exar Corporation 6 / 9 exar.com/xr9

7 Register Information Reg No. Hex Dec Name Function R/ W/ C Digital Part Control Register Byte of Parameter Parameter x NOP No operation C N/ Reset Default Code Power-up Condition Remark Does not execute a function. NOP is used to test successful I C communication x SW_RESET Software reset C N/ Resets all registers to default values Read ID x DEVICE_ID Read Device ID R x VERSION_ID Sleep in/out x4 4 x5 5 Basic Config SLEEP_OUT_ REG SLEEP_IN_ REG Read HW & SW version numbers Normal operating mode, system active R [5:]: report 9 in BCD [5:]: reserved [:8]: Hardware version # [7:]: Software version # x9 N/ C N/ ctive Sleep Mode C N/ ctive x6 6 Gain Gain select R/W [:]: Gain select x Gain = x7 7 LDO LDO Settings R/W x8 8 LDO Current Sense Select Channel Switch (Input Mux Select) []:LDO V,.65V []:LDO disable x LDO = V LDO Current Sense C N/ Off x 6 Select_Input_ Select Channel C Instructs the XR9 to report its device ID 9 in binary form ( ) Initial H/W version number is ; Initial S/W version number is. Puts the XR9 into active mode. (wake up) Puts the analog portion of the XR9 into sleep mode. During sleep mode, the only I C command that can be received/processed is the SLEEP_OUT command (x4). ll other register addresses will be ignored. Eight gain settings are selectable (from V/V to 76V/V), refer to the Gain Register Table for more information. Bit controls the LDO voltage (: V; :.65V). Bit (Sleep Mode only). Bit controls whether the LDO shuts down or stays on during Sleep Mode. (: Enable; : Disable). When the XR9 is active, the LDO is always on. When on, the LDO current is sensed and a proportional voltage is present at the output of the XR9. Current Sense Mode remains active until an input select command is received by the XR9. Select +IN, -IN; Channel x 7 Select_Input_ Select Channel C Select +IN, -IN; Channel x 8 Select_Input_ Select Channel C Select +IN, -IN; Channel x 9 Select_Input_4 Select Channel 4 C Select +IN4, -IN4; Channel 4 x4 Select_Input_5 Select Channel 5 C Select +IN5, -IN5; Channel 5 x5 Select_Input_6 Select Channel 6 C Select +IN6, -IN6; Channel 6 x6 Select_Input_7 Select Channel 7 C Select +IN7, -IN7; Channel 7 x7 Select_Input_8 Select Channel 8 C Channel Select +IN8, -IN8; Channel 8 N/ x8 4 Select_Input_9 Select Channel 9 C is selected Select +IN9, -IN9; Channel 9 x9 5 Select_Input_ Select Channel C Select +IN, -IN; Channel x 6 Select_Input_ Select Channel C Select +IN, -IN; Channel xb 7 Select_Input_ Select Channel C Select +IN, -IN; Channel xc 8 Select_Input_ Select Channel C Select +IN, -IN; Channel xd 9 Select_Input_4 Select Channel 4 C Select +IN4, -IN4; Channel 4 xe Select_Input_5 Select Channel 5 C Select +IN5, -IN5; Channel 5 xf Select_Input_6 Select Channel 6 C Select +IN6, -IN6; Channel 6 Note: Register Numbers not listed above have no function. 4-5 Exar Corporation 7 / 9 exar.com/xr9

8 Digital Part Control Register Reg No. Hex Dec Name Function R/ W/ C Byte of Parameter Parameter Default Code Power-up Condition Remark Offset DC Config x DC applied to Channel x DC applied to Channel x 4 DC applied to Channel x 5 DC4 applied to Channel 4 x4 6 DC5 applied to Channel 5 x5 7 DC6 applied to Channel 6 x6 8 DC7 x7 9 DC8 x8 4 DC9 applied to Channel 7 applied to Channel 8 applied to Channel 9 []: DC Sign [9:]: DC Range x mv offset Bit controls the sign of the DC offset voltage. Bits 9 thru control the value of the DC offset voltage. x9 4 DC applied to Channel []: DC Sign = positive; = negative x 4 DC applied to Channel xb 4 DC applied to Channel xc 44 DC applied to Channel xd 45 DC4 applied to Channel 4 xe 46 DC5 applied to Channel 5 xf 47 DC6 applied to Channel 6 Table : Register List Hex D D9 D8 D7 D6 D5 D4 D D D D Offset % of FS Input Voltage RTI xff 5 +56mV x x7ff -5-56mV x4 DC Sign -bit DC Range Table : DC Registers Hex D D D Gain x x x 4 x 8 x4 5 x5 x6 6 x7 76 Table : Gain Register 4-5 Exar Corporation 8 / 9 exar.com/xr9

9 Typical Performance Characteristics T = 5 C, V CC =.V, V DD =.8V, R L = kω to.5v; G = 76; unless otherwise noted. Small Signal Pulse Response at G = Large Signal Pulse Response at G = G =, Vout =.5Vpp G =, Vout =.5Vpp Time (µs) Time (µs) Small Signal Pulse Response at G = Large Signal Pulse Response at G = G =, Vout =.5Vpp G =, Vout =.5Vpp Time (µs) Time (µs) Frequency Response at G = Frequency Response at G = G = G = Normalized Gain (db) - -6 V OUT =.5V pp V OUT = V pp V OUT =.5V pp Normalized Gain (db) - -6 V OUT =.5V pp V OUT = V pp V OUT =.5V pp Frequency (khz) -. Frequency (khz) 4-5 Exar Corporation 9 / 9 exar.com/xr9

10 Typical Performance Characteristics T = 5 C, V CC =.V, V DD =.8V, R L = kω to.5v; G = 76; unless otherwise noted. LDO Current vs. Output Voltage LDO Output Current.5 4 G = Current Sense Mode ctive.5 V CC = 5V.5 VLDO (V).5.5 V CC =.V ILDO (m) 4 5 ILDO (m) Output Offset Voltage vs. Output Current Output Offset vs. Input Common Mode Voltage G =.5.5 G = G = 76 G = Output Current (m) Input Common Mode Voltage (V) Input Voltage Noise vs. Frequency.Hz to Hz RTI Voltage Noise.5 9 G = 76 Input Voltage Noise (nv/ Hz) Frequency (KHz) RTI Noise (µv) Time (sec) 4-5 Exar Corporation / 9 exar.com/xr9

11 Typical Performance Characteristics T = 5 C, V CC =.V, V DD =.8V, R L = kω to.5v; G = 76; unless otherwise noted. Sleep to Wake Time (DUT Output).5 G = Stop Time = % Settling.5 DUT OUTPUT SD.5 Start Time = 5% cknowledge Time (µs) Set-up Time - from G = to G = (DUT Output) 4.5 SD Stop Time = % Settling.5 DUT OUTPUT.5 Start Time = 5% cknowledge Time (µs) LDO Enable to Disable Time 4.5 LDO Disable to Enable Time SD LDO Output Stop Time = % Settling LDO OUTPUT Stop Time = % Settling SD Start Time = 5% cknowledge Time (µs) Start Time = 5% cknowledge Time (µs) 4-5 Exar Corporation / 9 exar.com/xr9

12 pplication Information Functional Block Diagram VCC LDO Output.5V Reference LDO Enable LDO Select ( V,.65V ) Input +/- Gnd Input +/- Input +/- PG Input 4 +/- 6: Differential Mux : Differential Mux Output Input 4 +/- Input 5 +/- Input 6 +/- VDD SD SCL Input [:5] Current Sense Mode DC [:9], Sign Offset - Offset + bit Offset DC IC Serial Digital Interface Gain Select LDO Enable LDO Select Power Down nalog DGnd Figure : Functional Block Diagram The XR9 sensor interface includes a 6: differential multiplexor (mux), a programmable gain instrumentation amplifier, a -bit offset correction DC and an LDO. n I C interface controls the many functions and features of the XR9. The XR9 is designed to integrate multiple bridge sensors with an DC/MCU or FPG. Each bridge sensor connected to the XR9 has its own inherent offset that if not calibrated out can decrease sensitivity and overall performance of the sensor system. The on-board DC introduces an offset into the instrumentation amplifier to calibrate the offset voltage generated by the sensors. n independent offset can be set for each of the 6 channels. Only the offset voltage of the active channel is applied to the PG. The programmable gain instrumentation amplifier offers 8 selectable gains from V/V to 76V/V to amplify the signal such that it falls within the input range of the DC. n integrated LDO provides a regulated voltage to power the input bridge sensors and is selectable, between V and.65v. The LDO can be set to turn off when the XR9 is in Sleep Mode to save power. The XR9 also provides the ability to monitor the LDO current. When the XR9 is in Current Sense Mode, an internal : mux allows a voltage proportional to the LDO current to be present at the output. Once all channels have been calibrated, the LDO current can be used to indirectly monitor any voltage or resistive changes seen by the inputs. The XR9 also includes an internal.5v reference that is used by the internal LDO circuitry and used to set the reference voltage for the programmable gain instrumentation amplifier. During sleep mode, the analog components of the XR9 are powered down for added power savings. The XR9 offers many functions, each controlled by the IC compatible serial interface: Input Selection Gain Selection Offset Correction LDO Enable / Select Current Sense Mode Sleep Mode (nalog Power Down) Refer to the appropriate section below for additional information about each function. 4-5 Exar Corporation / 9 exar.com/xr9

13 I C Bus Interface The I C-bus interface consists of two lines: serial data (SD) and serial clock (SCL). The XR9 works as a slave and supports both standard mode transfer rates ( kbps) and fast mode transfer rates (4 kbps) as defined in the I C- Bus specification. The I C-bus interface follows all standard I C protocols. Some information is provided below, for additional information, refer to the I C-bus specifications. Figures 4 and 5 illustrate a write and a read cycle. For complete details, see the IC-bus specifications. S SLVE DDRESS W White Block = host to XR9 Red Block = XR9 to host REGISTER DDRESS ndt P Figure 4: Master Writes to Slave (XR9) Figure : I C Start and Stop Conditions The basic I C access cycle for the XR9 consists of: start condition slave address cycle Zero, one, or two data cycles - depending on the XR9 register accessed stop condition Start Condition - The master initiates data transfer by generating a start condition. The start condition is when a high-to-low transition occurs on the SD line while SCL is high, as shown in Figure. Slave ddress Cycle fter the start condition, the first byte sent by the master is the 7-bit address and the read/ write direction bit R/W on the SD line. If the address matches the XR9 s internal fixed address, the XR9 will respond with an acknowledge by pulling the SD line low for one clock cycle while SCL is high. Data Cycle fter the master detects this acknowledge, the next byte transmitted by the master is the sub-address. This 8-bit sub-address contains the address of the register to access. The XR9 Register List is shown in Table. Depending on the register accessed, there will be up to two additional data bytes transmitted by the master. Refer to the Byte of Parameter column in the Register Table. The XR9 will respond to each write with an acknowledge. S SLVE DDRESS W White Block = host to XR9 Red Block = XR9 to host REGISTER DDRESS S SLVE LST R ndt DDRESS DT N P Figure 5: Master Reads from Slave (XR9) I C Bus ddressing The XR9 uses a 7-bit address space. For the standard XR9, the default address is x67 ( ). IC ddress x67 ( x) Orderable Part# XR9IL4TR-F Table 4: XR9 I C ddress Map read or write transaction is determined by bit- of the slave address, (shown as an x in Table above). If bit- is, then it is a write transaction. If bit- is, then it is a read transaction. n IC sub-address is sent by the IC master following the slave address. The sub-address contains the XR9 register address being accessed. Table illustrates the available XR9 register addresses. fter the last read or write transaction, the IC-bus master will set the SCL signal back to its idle state (HIGH). Stop Condition To signal the end of the data transfer, the master generates a stop condition by pulling the SD line from low to high while the SCL line is high, as shown in Figure. 4-5 Exar Corporation / 9 exar.com/xr9

14 Inputs and Input Selection The XR9 includes 6 differential inputs and a 6: differential mux that is controlled by an I C compatible wire serial interface. The XR9 is designed to accept 6 differential inputs. If fewer than 6 differential inputs are required, tie the unused inputs to GND. If single ended inputs are required, tie the unused inputs to.5v. The input common mode range of the XR9 is typically.6v to.4v when running from a.v supply. The XR9 offers a very wide gain range. In most cases, the output voltage swing will be the limiting factor. When the XR9 is powered-up, the default input selected is Channel. Inputs are selected via I C using one of 6 register addresses x thru xf. Refer to the Register List in Table. Example: The example below illustrates how to select Channel 5. Step Master sends start condition S Gain Selection The XR9 offers 8 selectable fixed gains ranging from V/V to 76V/V. When the XR9 is powered-up, the default gain is V/V. The gain is selected via I C using the register address x6 followed by another byte of data to select the gain. Refer to the Register List in Table and the Gain Register list in Table. Example: The example below illustrates how to select a gain of 5V/V. To start communication with the XR9, repeat steps - as shown in the Inputs and Input Selection section on page. Step Master sends address of register to access Step 5 9 XR9 sends acknowledge Gain Select register address = x6 Step Master sends XR9 address with write bit Step 9 XR9 sends acknowledge 6 7 W 7-bit XR9 ddress = x67 Step Master sends address of register to access Step 5 9 XR9 sends acknowledge Step 6 Master sends stop condition White Block = host to XR9 Red Block = XR9 to host Grey Block = Notes Select_Input 5 register address = x4 P Since the Gain Select register was accessed, the XR9 is expecting another byte of data from the master to complete the command. Refer to the Byte of Parameter column in the Register List (Table ). D thru D are used to select the gain. Refer to the Gain Register list in Table, 5V/V is D =, D =, and D =. This translates to a hex code of x4, since a full byte of data (8-bits) will be sent. Step Master sends gain register data to select G=5 Step 7 9 XR9 sends acknowledge Step 8 Master sends stop condition White Block = host to XR9 Red Block = XR9 to host Grey Block = Notes P Gain of 5V/V = x4 4-5 Exar Corporation 4 / 9 exar.com/xr9

15 Offset Correction The XR9 has a -bit offset correction DC that can be used to provide digital calibration on each of the 6 inputs. Only the offset voltage of the active channel is applied to the PG. The DC offset of each channel is controlled by the IC compatible interface. t any time, the master can read or write to any of the DC offset registers. The DC offset for each channel is set via IC using the register addresses x thru xf followed by another two bytes of data to set the polarity and value of the offset voltage. Refer to the Register List in Table. ±56mV offset correction range is available. The full range of the DC offset is only available at a gain of. t higher gains, the output voltage range of the XR9 will be exceeded if the full range of the DC offset is used. The internal -bit DC allows,4 different offset voltage settings between mv and 56mV. The polarity of the offset correction is set with an additional bit. The unit offset is determined by the following: Unit offset = Total Offset = 56mV = DC outputlevels 4 547nV Step 5 9 XR9 sends acknowledge Since a DC Offset register was accessed, the XR9 is expecting another two bytes of data from the master to complete the command. Refer to the Byte of Parameter column in the Register List (Table ). D thru D9 are used to set the offset voltage and D is used to set the sign of the offset voltage, = positive and = negative. Refer to the DC Offset register list in Table. To determine what DC output level corresponds to 75mV, use the following equation: DC Output Level = Desired Offset = 75mV = Unit Offset 547 V 7 n decimal value of 7 corresponds to 75mV. Therefore: x89 (hex) or (binary) applies a +75mV offset x489 (hex) or (binary) applies a -75mV offset From Table : x (hex) or (binary) applies a mv offset xff (hex) or (binary) applies a +56mV offset x7ff (hex) or (binary) applies a -56mV offset Step Master sends st byte of DC offset register data to select an offset of +75mV Sign MSBs of -bit DC output level that corresponds to 7 (x89) Each DC output level provides an additional 547µV of offset. To determine what DC output level corresponds to a specific desired offset, use the following equation: See example below for additional information. Example: The example below illustrates how to set the DC offset for channel 7 to a value of 75mV. To start communication with the XR9, repeat steps - as shown in the Inputs and Input Selection section on page. Step Master sends address of register to access DC7 register address = x6 Step 7 9 XR9 sends acknowledge Step Master sends nd byte of DC offset register data to select an offset of +75mV Step 9 9 XR9 sends acknowledge Step Master sends stop condition White Block = host to XR9 Red Block = XR9 to host Grey Block = Notes 8 LSBs of -bit DC output level that corresponds to 7 (x89) P 4-5 Exar Corporation 5 / 9 exar.com/xr9

16 LDO Enable / Select (Power to External Bridge Sensors) The XR9 includes an on-board LDO that provides a regulated voltage that can be used to power external input bridge sensors. Two voltage options are available, V and.65v. The LDO voltage is selected via the IC compatible two-wire serial interface. When the XR9 is powered-up, the default LDO voltage is V. When the XR9 is active (not in sleep mode), the LDO is always on. If the LDO voltage is not used, the LDO output can be left floating. The LDO can either stay on or shut down while the XR9 is in Sleep Mode. Set LDO to shut down while XR9 is in Sleep Mode to save power Set LDO to stay on while XR9 is in Sleep Mode to improve wake-up time The LDO voltage and disable setting are selected via IC using the register address x7 followed by another byte of data to select the voltage and disable setting. Refer to the Register List in Table and the example below for more information. Example: The example below illustrates how to select an LDO voltage of.65v and keep the LDO enabled during Sleep Mode. To start communication with the XR9, repeat steps - as shown in the Inputs and Input Selection section on page. Step Master sends address of register to access Step 5 9 XR9 sends acknowledge LDO Settings register address = x7 Since the LDO Settings register was accessed, the XR9 is expecting another byte of data from the master to complete the command. Refer to the Byte of Parameter column in the Register List (Table ). D and D are used to select the LDO voltage and enable/disable the LDO during Sleep Mode. Bit (D) controls the LDO voltage (: V; :.65V). Bit (D) is only applicable in Sleep Mode. Bit controls whether the LDO shuts down or stays on during sleep mode (: Enable; : Disable). When the XR9 is active, the LDO is always on. Step Master sends code to select LDO voltage of.65v and Enable LDO during Sleep Mode Step 7 9 XR9 sends acknowledge Step 8 Master sends stop condition White Block = host to XR9 Red Block = XR9 to host Grey Block = Notes P = Enable =.65V Current Sense Mode (Monitoring the LDO Current) Current Sense Mode is activated via IC using the register address x8. When activated, the LDO current is sensed and a proportional voltage is present at the output of the XR9 (ILDO = VOUT/RL). Current Sense Mode stays active until the XR9 receives any input select command (x thru xf). Current sense mode can be used to monitor the change over time of the bridge impedance. Sleep Mode (nalog Power Down) Sleep Mode is activated via I C using the register address x5. When activated, the XR9 will enter Sleep Mode. During Sleep Mode, the analog portion of the XR9 is disabled. ll register settings are retained during Sleep Mode. During Sleep Mode, the nominal supply current will drop below 7µ (with LDO on) and below 45µ (with LDO off). During Sleep Mode, the master can read the value in any register that saves a value during sleep mode. The only I C commands that can be received or processed is the SLEEP_OUT (wake up) command (x4) or the LDO on/off and voltage command (x7). ll other register addresses will be ignored. Register address x4 is used to return to normal operation (exit Sleep Mode). By default, the XR9 is active. 4-5 Exar Corporation 6 / 9 exar.com/xr9

17 Typical pplication 6: Bridge Sensor Interface The XR9 was designed to interface multiple bridge sensors with a microcontroller or FPG as illustrated in Figure 6. The bridge output signal is differential (Vo+ and Vo-). Ideally, the unloaded bridge output is zero (Vo+ and Voare identical). However, in-exact resistive values result in a difference between Vo+ and Vo-. This bridge offset voltage can be substantial and vary between sensors. The XR9 provides the ability to calibrate the bridge offset on each of the 6 bridge sensors using the on-board DC. BRDG VCC Bridge 6 IN6+ LDO IN6- IN / PG OUT DC µc 6: MUX ±56mV offset trim Bridge IN+ IN- -bit DC XR9 PG IC Control SD SCL Figure 6: 6: Bridge Sensor Interface Layout Considerations General layout and supply bypassing play major roles in high frequency performance. Follow the steps below as a basis for high frequency layout: Include 6.8µF and.µf ceramic capacitors for power supply decoupling Place the 6.8µF capacitor within.75 inches of the power pin Place the.µf capacitor within. inches of the power pin Connection to the exposed pad is not required. Exposed pad can be connected to ground (GND). Minimize all trace lengths to reduce series inductances 4-5 Exar Corporation 7 / 9 exar.com/xr9

18 Mechanical Dimensions QFN-4 Package FOR REFERENCE ONLY ECN: 5-5 /6/ 4-5 Exar Corporation 8 / 9 exar.com/xr9

19 Ordering Information Part Number Package Green Operating Temperature Range Packaging XR9IL4-F QFN-4 Yes -4 C to +85 C Tray XR9IL4TR-F QFN-4 Yes -4 C to +85 C Tape & Reel XR9IL4EVB Evaluation Board N/ N/ N/ For Further ssistance: CustomerSupport@exar.com or HPTechSupport@exar.com Exar Technical Documentation: Exar Corporation Headquarters and Sales Offices 4876 Kato Road Tel.: + (5) Fremont, C US Fax: + (5) NOTICE EXR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXR Corporation is prohibited. 4-5 Exar Corporation 9 / 9 exar.com/xr9