Datasheet ZSSC3240 (Renesas) - 37

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ZSSC3240 Symbol Parameter Typical Value Unit Comments
β Current gain of external-loop TLOOP 100 Numeric bipolar transistor, TLOOP Transfer bandwidth of internal BWL 20 kHz current loop op amp. With a ratiometric supply and resistances that are too low, the overall current consumption External sensor element’s (I R Sensor + IIC) at VDD could exceed the 4mA low- SENSOR,MIN 1.6 kΩ minimum resistance limit for typical current loops (see Table 3 for ISensor specifications, and see Table 4 for IIC specifications) Loop-response current for Effective current modulation when ZSSC3240 is ILoop,high 14…18 mA logical-1; OWI over current-loop OWI slave modulating the slave-to-master Loop-response current for response via the loop current (controlled by ILoop,low 4…6 mA logical-0; OWI over current-loop AOUT/OWI1) Strong recommendation: Use the Zener diode between FB and VDD to protect the VDD line from positive over- voltage conditions and protect the FB input from negative over-voltages. The 100nF capacitor performs a low- pass-filter function for short / fast changes in the total current consumption for the sensor element plus the ZSSC3240 (ISENS + IIC), such that current consumption changes do not lead to short-term fluctuations of AOUT and the loop current. An equivalent effect of slight loop current fluctuations might be observable if a sensor-connection check is sometimes executed between the normal sensor measurements. Here, the connected sensor element, e.g., a resistive bridge, will be unsupplied briefly in order to determine the electrical connection properties; whereas an overall load change (sensor measurements → sensor-connection check → sensor-measurement) at VDD and hence in the current loop will be present. Therefore, diagnostic features should be carefully enabled and selected for current loop applications that have strong requirements for output signal quality under any circumstances.
ISENSOR+ IIC < 4mA !
VDD (VDD~5V) JFET Loop+ 7 to 48V LDO Cont rol / Regulat ion LDOct rl detect 13-16 bit Iloop A 100n
D
IDAC +
A
Tloop V AO UT loop -
ISENSOR+ IIC
VSS R1 Rsens ILoop Loop- FB 4..20mA
Figure 20. Current Loop Configuration 6.5.4. Output Interrupt Signaling
The EOC pin can be programmed to operate either as a simple “measurement busy” and end-of-conversion transducer or as a configurable interrupt transducer, which is configured using the INT_setup[1:0] bits in NVM register 02HEX, bits[8:7]. Further, one or two 24-bit quantized thresholds can be programmed via TRSH1 and TRSH2 (Interrupt Level Setup registers 18HEX, 19HEX and 1AHEX in NVM; see Table 34). Depending on the INT_setup selection, the EOC pin provides a logic 1 or logic 0 (also dependent on the respective interface setup; Apr.15.20 Page 37 Document Outline 1. Pin Assignments 2. Pin Descriptions 3. Absolute Maximum Ratings 4. Recommended Operating Conditions 5. Electrical Characteristics 6. Device Description 6.1 Signal Flow 6.2 Analog (Sensor) Front-End 6.2.1. Programmable-Gain Amplifier (PGA) 6.2.2. Analog-to-Digital Converter (ADC) 6.2.3. Internal Temperature Sensor 6.2.4. Supported Supplies for Sensor Elements and Additional, External Temperature Sensing 6.3 On-Chip Diagnostics 6.4 Digital Interfaces 6.4.1. SPI 6.4.2. I2C 6.4.3. One-Wire-Interface, OWI 6.5 Measurement and Output Options 6.5.1. Single Measurements, Digital Raw Results, and SSC Results 6.5.2. Cyclic, Continuous, Repeated Measurements – Measurement Scheduler 6.5.3. Analog Outputs: Digital-to-Analog Converter (DAC) 6.5.4. Output Interrupt Signaling 6.6 System Setup and Control 6.6.1. Digital Commands 6.6.2. Nonvolatile Memory (NVM) 6.6.3. Digital Sensor-Signal-Conditioning Mathematics 6.7 External, Extra LDO (LDOctrl) for Applications for > 5.5V 7. Calibration 8. Package Outline Drawings 9. Marking Diagram 10. Ordering Information 11. Glossary 12. Revision History