Datasheet LTC2500-32 (Analog Devices) - 34

LTC2500-32
APPLICATIONS INFORMATION
C[11] and C[10] are used during the programming of
Programming the Configuration
the LTC2500-32 and do not control the configuration of A transaction window opens at power-up, at the falling edge the digital filter or ADC. Bits C[3:0] select the filter type. of DRL, at the falling edge of a RDLA pulse, or when the Bits C[7:4] select the down-sampling factor (DF). C[8] filter configuration is reset using a SYNC pulse. A trans- enables/disables digital gain expansion (DGE) and C[9] action window opening allows the filter configuration of enables/disables digital gain compression (DGC). Table 3 the LTC2500-32 to be programmed. Once the transaction summarizes the configuration options. window opens, the state machine controlling the program-
Table 3. Configuration Option Summary
ming of the configuration is in a reset state, waiting for a
BITS VALUE SETTING
control word to be shifted in at SDI on the first 12 SCKA C[3:0] = FILTER TYPE 0001 SINC1 clock pulses. The transaction window closes at the start 0010 SINC2 of the next conversion when DRL transitions from low 0011 SINC3 to high as shown in Figure 32, or at the end of the 12th 0100 SINC4 0101 SSINC SCKA pulse since the transition window opened. Serial 0110 FLAT PASSBAND input data at SDI should be avoided when BUSY is high. 0111 AVERAGING OTHER CODES INVALID CODE
Input Control Word
C[7:4] = DF 0010 4 0011 8 The input control word is used to determine whether or 0100 16 0101 32 not the configuration is programmed. In many cases, the 0110 64 user will simply need to configure the converter once for 0111 128 1000 256 their specific application after power-up and then drive 1001 512 the SDI pin to GND. This will force the control word bits 1010 1024 to all zeros and the LTC2500-32 will operate with the 1011 2048 1100 4096 programmed configuration. 1101 8192 1110 16384 The control word is a 12-bit word as described in the OTHER CODES INVALID CODE LTC2500-32 control word section. A valid input control C[8] = DGE 0 DGE OFF word is one where C[11:10] = 10 and the remaining lower 1 DGE ON C[9] = DGC 0 DGC OFF 1 DGC ON MCLK DRL 250032 F32 TRANSACTION WINDOW
Figure 32. Sequencer Programming Transaction Window
250032fb 34 For more information www.linear.com/LTC2500-32 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Converter Characteristics for Filtered Output (SDOA) Dynamic Accuracy for Filtered Output (SDOA) Converter Characteristics for No latency Output (SDOB) Dynamic Accuracy for No Latency Output (SDOB) Reference Input Digital Inputs and Digital Outputs Power Requirements ADC Timing Characteristics Typical Performance Characteristics Pin Functions Functional Block Diagram Timing Diagram Applications Information Overview Converter Operation Transfer Function Analog Input Input Drive Circuits ADC Reference Dynamic Performance Power Considerations Timing and Control Decimation Filters Digital Filter Types Digital Interface Preset Filter Modes Filtered Output Data No Latency Output Data Board Layout Package Description Revision History Typical Application Related Parts