LTC2369-18 PIN FUNCTIONSCHAIN (Pin 1): Chain Mode Selector Pin. When low, the BUSY (Pin 11): BUSY Indicator. Goes high at the start of LTC2369-18 operates in normal mode and the RDL/SDI a new conversion and returns low when the conversion input pin functions to enable or disable SDO. When high, has finished. Logic levels are determined by OVDD. the LTC2369-18 operates in chain mode and the RDL/SDI RDL/SDI (Pin 12): When CHAIN is low, the part is in nor- pin functions as SDI, the daisy-chain serial data input. mal mode and the pin is treated as a bus enabling input. Logic levels are determined by OVDD. When CHAIN is high, the part is in chain mode and the VDD (Pin 2): 2.5V Power Supply. The range of VDD is pin is treated as a serial data input pin where data from 2.375V to 2.625V. Bypass VDD to GND with a 10μF ceramic another ADC in the daisy chain is input. Logic levels are capacitor. determined by OVDD. GND (Pins 3, 6, 10 and 16): Ground. SCK (Pin 13): Serial Data Clock Input. When SDO is enabled, the conversion result or daisy-chain data from another IN+ (Pin 4): Analog Input. IN+ operates differential with ADC is shifted out on the rising edges of this clock MSB respect to IN– with an IN+-IN– range of 0V to VREF. first. Logic levels are determined by OVDD. IN– (Pin 5): Analog Ground Sense. IN– has an input range SDO (Pin 14): Serial Data Output. The conversion result of ±100mV with respect to GND and must be tied to the or daisy-chain data is output on this pin on each rising ground plane or a remote ground sense. edge of SCK MSB first. The output data is in straight binary REF (Pins 7, 8): Reference Inputs. The range of REF is 2.5V format. Logic levels are determined by OVDD. to 5.1V. This pin is referred to the GND pin and should be OV decoupled closely to the pin with a 47μF ceramic capacitor DD (Pin 15): I/O Interface Digital Power. The range of OV (X5R, 0805 size). DD is 1.71V to 5.25V. This supply is nominally set to the same supply as the host interface (1.8V, 2.5V, 3.3V, CNV (Pin 9): Convert Input. A rising edge on this input or 5V). Bypass OVDD to GND with a 0.1μF capacitor. powers up the part and initiates a new conversion. Logic GND (Exposed Pad Pin 17, DFN Package Only): Ground. levels are determined by OVDD. Exposed pad must be soldered directly to the ground plane. 236918fa 8