Datasheet LTC2313-14 (Analog Devices) - 10

LTC2313-14
applicaTions inForMaTion Overview Serial Data Output (SDO)
The LTC2313-14 is a low noise, high speed, 14-bit succes- The SDO output is always forced into the high impedance sive approximation register (SAR) ADC. The LTC2313-14 state while CONV is high. The falling edge of CONV enables operates from a single 3V or 5V supply and provides a low SDO and also places the sample and hold into sample drift (20ppm/°C maximum), internal reference and refer- mode. The A/D conversion result is shifted out on the SDO ence buffer. The internal reference buffer is automatically pin as a serial data stream with the MSB first. The MSB configured with a 2.048V span in low supply range (2.7V is output on SDO on the falling edge of CONV. Delay t3 to 3.6V) and with a 4.096V span in the high supply range is the data valid access time for the MSB. The following (4.75V to 5.25V). The LTC2313-14 samples at a 2.5Msps 13 bits of conversion data are shifted out on SDO on the rate and supports a 90MHz serial data read clock. The falling edge of SCK. Delay t4 is the data valid access time LTC2313-14 achieves excellent dynamic performance for output data shifted out on the falling edge of SCK. (77dB SINAD, 85dB THD) while dissipating only 25mW There is no cycle latency. Subsequent falling SCK edges from a 5V supply at the 2.5Msps conversion rate. The applied after the LSB is output will output zeros indefinitely LTC2313-14 outputs the conversion data with no cycle on the SDO pin. latency onto the SDO pin. The SDO pin output logic lev- The output swing on the SDO pin is controlled by the els are supplied by the dedicated OVDD supply pin which OV has a wide supply range (1.71V to 5.25V) allowing the DD pin voltage and supports a wide operating range from 1.71V to 5.25V independent of the V LTC2313-14 to communicate with 1.8V, 2.5V, 3V or 5V DD pin voltage. systems. The LTC2313-14 automatically switches to nap
Power Considerations
mode following the conversion process to save power. The device also provides a sleep power-down mode through The LTC2313-14 provides two sets of power supply pins: serial interface control to reduce power dissipation during the analog power supply (VDD) and the digital input/output long inactive periods. interface power supply (OVDD). The flexible OVDD supply allows the LTC2313-14 to communicate with any digital
Serial Interface
logic operating between 1.8V and 5V, including 2.5V and 3.3V systems. The LTC2313-14 communicates with microcontrollers, DSPs and other external circuitry via a 3-wire interface.
Entering Nap/Sleep Mode
A rising CONV edge starts the conversion process which is timed via an internal oscillator. Following the conver- Pulsing CONV two times and holding SCK static places the sion process the device automatically switches to nap LTC2313-14 into nap mode. Pulsing CONV four times and mode to save power as shown in Figure 7. This feature holding SCK static places the LTC2313-14 into sleep mode. saves considerable power for the LTC2313-14 operating In sleep mode, all bias circuitry is shut down, including the at lower sampling rates. As shown in Figures 5 and 6, it internal bandgap and reference buffer, and only leakage is recommended to hold SCK static low or high during currents remain (0.2µA typical). Because the reference t buffer is externally bypassed with a large capacitor (2.2µF), CONV. CONV must be held high for the entire minimum conversion time (t the LTC2313-14 requires a significant wait time (1.1ms) to CONV). A falling CONV edge enables SDO and outputs the MSB. Subsequent SCK falling edges clock recharge this capacitance before an accurate conversion out the remaining data as shown in Figures 5 and 6. Data can be made. In contrast, nap mode does not power down is serially output MSB first through LSB last, followed the internal bandgap or reference buffer allowing for a fast by trailing zeros if further SCK falling edges are applied. wake-up and accurate conversion within one conversion clock cycle. Supply current during nap mode is nominally 2mA. 231314fb 10 For more information www.linear.com/LTC2313-14 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Converter Characteristics Dynamic Accuracy Reference Input/Output Digital Inputs and Digital Outputs Power Requirements ADC Timing Characteristics Typical Performance Characteristics Pin Functions Block Diagram Timing Diagrams Applications Information Package Description Related Parts