Datasheet LTC2378-20 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | 20-Bit, 1Msps, Low Power SAR ADC with 0.5ppm INL |
| Pages / Page | 28 / 9 — TiMing DiagraM. Conversion Timing Using the Serial Interface. … |
| File Format / Size | PDF / 1.0 Mb |
| Document Language | English |
TiMing DiagraM. Conversion Timing Using the Serial Interface. applicaTions inForMaTion. OVERVIEW. CONVERTER OPERATION
Model Line for this Datasheet
- LTC2378CDE-20#PBF LTC2378CDE-20#PBF LTC2378CDE-20#TRPBF LTC2378CDE-20#TRPBF LTC2378CMS-20#PBF LTC2378CMS-20#PBF LTC2378CMS-20#TRPBF LTC2378CMS-20#TRPBF LTC2378IDE-20#PBF LTC2378IDE-20#PBF LTC2378IDE-20#TRPBF LTC2378IDE-20#TRPBF LTC2378IMS-20#PBF LTC2378IMS-20#PBF LTC2378IMS-20#TRPBF LTC2378IMS-20#TRPBF
Text Version of Document
LTC2378-20
TiMing DiagraM Conversion Timing Using the Serial Interface
CHAIN, RDL/SDI = 0 CNV POWER-DOWN AND ACQUIRE BUSY CONVERT SCK D19 D18 D17 D16 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 SDO 237820 TD01
applicaTions inForMaTion OVERVIEW CONVERTER OPERATION
The LTC2378-20 is a low noise, low power, high speed The LTC2378-20 operates in two phases. During the ac- 20-bit successive approximation register (SAR) ADC. quisition phase, the charge redistribution capacitor D/A Operating from a single 2.5V supply, the LTC2378-20 converter (CDAC) is connected to the IN+ and IN– pins supports a large and flexible ±VREF fully differential input to sample the differential analog input voltage. A rising range with VREF ranging from 2.5V to 5.1V, making it ideal edge on the CNV pin initiates a conversion. During the for high performance applications which require a wide conversion phase, the 20-bit CDAC is sequenced through a dynamic range. The LTC2378-20 achieves ±2ppm INL successive approximation algorithm, effectively comparing maximum, no missing codes at 20 bits and 104dB SNR. the sampled input with binary-weighted fractions of the Fast 1Msps throughput with no cycle latency makes the reference voltage (e.g. VREF/2, VREF/4 … VREF/1048576) LTC2378-20 ideally suited for a wide variety of high speed using the differential comparator. At the end of conversion, applications. An internal oscillator sets the conversion time, the CDAC output approximates the sampled analog input. easing external timing considerations. The LTC2378-20 The ADC control logic then prepares the 20-bit digital dissipates only 21mW at 1Msps, while an auto power-down output code for serial transfer. feature is provided to further reduce power dissipation during inactive periods.
TRANSFER FUNCTION
The LTC2378-20 features a unique digital gain compres- The LTC2378-20 digitizes the full-scale voltage of 2 × REF sion (DGC) function, which eliminates the driver amplifier’s into 220 levels, resulting in an LSB size of 9.5µV with negative supply while preserving the full resolution of the REF = 5V. Note that 1 LSB at 20 bits is approximately ADC. When enabled, the ADC performs a digital scaling 1ppm. The ideal transfer function is shown in Figure 2. function that maps zero-scale code from 0V to 0.1 • VREF The output data is in 2’s complement format. and full-scale code from VREF to 0.9 • VREF. For a typical reference voltage of 5V, the full-scale input range is now
ANALOG INPUT
0.5V to 4.5V, which provides adequate headroom for powering the driving amplifier from a single 5.5V supply. The analog inputs of the LTC2378-20 are fully differential in order to maximize the signal swing that can be digitized. The analog inputs can be modeled by the equivalent circuit 237820fb For more information www.linear.com/LTC2378-20 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Converter Characteristics Dynamic Accuracy Reference Input Digital Inputs and Digital Outputs Power Requirements ADC Timing Characteristics Typical Performance Characteristics Pin Functions Functional Block Diagram Timing Diagram Applications Information Board Layout Package Description Revision History Typical Application Related Parts
TiMing DiagraM Conversion Timing Using the Serial Interface
CHAIN, RDL/SDI = 0 CNV POWER-DOWN AND ACQUIRE BUSY CONVERT SCK D19 D18 D17 D16 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 SDO 237820 TD01
applicaTions inForMaTion OVERVIEW CONVERTER OPERATION
The LTC2378-20 is a low noise, low power, high speed The LTC2378-20 operates in two phases. During the ac- 20-bit successive approximation register (SAR) ADC. quisition phase, the charge redistribution capacitor D/A Operating from a single 2.5V supply, the LTC2378-20 converter (CDAC) is connected to the IN+ and IN– pins supports a large and flexible ±VREF fully differential input to sample the differential analog input voltage. A rising range with VREF ranging from 2.5V to 5.1V, making it ideal edge on the CNV pin initiates a conversion. During the for high performance applications which require a wide conversion phase, the 20-bit CDAC is sequenced through a dynamic range. The LTC2378-20 achieves ±2ppm INL successive approximation algorithm, effectively comparing maximum, no missing codes at 20 bits and 104dB SNR. the sampled input with binary-weighted fractions of the Fast 1Msps throughput with no cycle latency makes the reference voltage (e.g. VREF/2, VREF/4 … VREF/1048576) LTC2378-20 ideally suited for a wide variety of high speed using the differential comparator. At the end of conversion, applications. An internal oscillator sets the conversion time, the CDAC output approximates the sampled analog input. easing external timing considerations. The LTC2378-20 The ADC control logic then prepares the 20-bit digital dissipates only 21mW at 1Msps, while an auto power-down output code for serial transfer. feature is provided to further reduce power dissipation during inactive periods.
TRANSFER FUNCTION
The LTC2378-20 features a unique digital gain compres- The LTC2378-20 digitizes the full-scale voltage of 2 × REF sion (DGC) function, which eliminates the driver amplifier’s into 220 levels, resulting in an LSB size of 9.5µV with negative supply while preserving the full resolution of the REF = 5V. Note that 1 LSB at 20 bits is approximately ADC. When enabled, the ADC performs a digital scaling 1ppm. The ideal transfer function is shown in Figure 2. function that maps zero-scale code from 0V to 0.1 • VREF The output data is in 2’s complement format. and full-scale code from VREF to 0.9 • VREF. For a typical reference voltage of 5V, the full-scale input range is now
ANALOG INPUT
0.5V to 4.5V, which provides adequate headroom for powering the driving amplifier from a single 5.5V supply. The analog inputs of the LTC2378-20 are fully differential in order to maximize the signal swing that can be digitized. The analog inputs can be modeled by the equivalent circuit 237820fb For more information www.linear.com/LTC2378-20 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Converter Characteristics Dynamic Accuracy Reference Input Digital Inputs and Digital Outputs Power Requirements ADC Timing Characteristics Typical Performance Characteristics Pin Functions Functional Block Diagram Timing Diagram Applications Information Board Layout Package Description Revision History Typical Application Related Parts
