CS5531/32/33/34-AS 16-bit and 24-bit ADCs with Ultra-low-noise PGIA Features General Description The CS5531/32/33/34 are highly integrated Analog- Chopper-stabilized PGIA (Programmable to-Digital Converters (ADCs) which use charge-balance Gain Instrumentation Amplifier, 1x to 64x) techniques to achieve 16-bit (CS5531/33) and 24-bit 12 nV/Hz 0.1 Hz (No 1/f noise) at 64x (CS5532/34) performance. The ADCs are optimized for 1200 pA Input Current with Gains >1 measuring low-level unipolar or bipolar signals in weigh scale, process control, scientific, and medical Delta-sigma Analog-to-digital Converter applications. Linearity Error: 0.0007% FS Noise Free Resolution: Up to 23 bits To accommodate these applications, the ADCs come as either two-channel (CS5531/32) or four-channel Two- or Four-channel Differential MUX (CS5533/34) devices and include a very low noise chop- per-stabilized instrumentation amplifier (6 nV/Hz 0.1 Scalable Input Span via Calibration Hz) with selectable gains of 1, 2, 4, 8, 16, 32, and 5 mV to differential 2.5V 64. These ADCs also include a fourth order modu- lator followed by a digital filter which provides twenty Scalable V Input: Up to Analog Supply REF selectable output word rates of 6.25, 7.5, 12.5, 15, 25, 30, 50, 60, 100, 120, 200, 240, 400, 480, 800, 960, 1600, Simple Three-wire Serial Interface 1920, 3200, and 3840 Sps (MCLK = 4.9152 MHz). SPI and Microwire Compatible Schmitt Trigger on Serial Clock (SCLK) To ease communication between the ADCs and a micro- controller, the converters include a simple three-wire se- R/W Calibration Registers Per Channel rial interface which is SPI and Microwire compatible with a Schmitt-trigger input on the serial clock (SCLK). Selectable Word Rates: 6.25 to 3,840 Sps High dynamic range, programmable output rates, and Selectable 50 or 60 Hz Rejection flexible power supply options makes these ADCs ideal solutions for weigh scale and process control Power Supply Configurations applications. VA+ = +5 V VA- = 0 V VD+ = +3 V to +5 V VA+ = +2.5 V VA- = -2.5 V VD+ = +3 V to +5 V ORDERING INFORMATION VA+ = +3 V VA- = -3 V VD+ = +3 V See page 47 VA+ C1 C2 VREF+ VREF- VD+ CS AIN1+ DIFFERENTIAL PGIA PROGRAMMABLE TH 4 ORDER 1,2,4,8,16 SDI AIN1- SINC FIR FILTER SERIAL 32,64 MODULATOR INTERFACE SDO AIN2+ MUX SCLK AIN2- (CS5533/34 AIN3+ SHOWN) AIN3- CLOCK CALIBRATION GENERATOR AIN4+ LATCH SRAM/CONTROL LOGIC AIN4- VA- A0/GUARD A1 OSC1 OSC2 DGND OCT 08 Copyright Cirrus Logic, Inc. 2008 CS5531/32/33/34-AS TABLE OF CONTENTS 1. CHARACTERISTICS AND SPECIFICATIONS ..........................................................4 ANALOG CHARACTERISTICS..........................................................................4 TYPICAL RMS NOISE (NV), CS5531/32/33/34 .................................................7 TYPICAL NOISE-FREE RESOLUTION(BITS), CS5532/34...............................7 5 V DIGITAL CHARACTERISTICS ....................................................................8 3 V DIGITAL CHARACTERISTICS ....................................................................8 DYNAMIC CHARACTERISTICS ........................................................................9 ABSOLUTE MAXIMUM RATINGS .....................................................................9 SWITCHING CHARACTERISTICS ..................................................................10 2. GENERAL DESCRIPTION .......................................................................................12 2.1. Analog Input ....................................................................................................12 2.1.1. Analog Input Span .................................................................................... 13 2.1.2. Multiplexed Settling Limitations ............................................................13 2.1.3. Voltage Noise Density Performance .....................................................13 2.1.4. No Offset DAC ......................................................................................14 2.2. Overview of ADC Register Structure and Operating Modes ............................14 2.2.1. System Initialization ..............................................................................15 2.2.2. Serial Port Interface ..............................................................................22 2.2.3. Reading/Writing On-Chip Registers ......................................................23 2.3. Configuration Register .....................................................................................23 2.3.1. Power Consumption .............................................................................23 2.3.2. System Reset Sequence ......................................................................23 2.3.3. Input Short ............................................................................................24 2.3.4. Guard Signal .........................................................................................24 2.3.5. Voltage Reference Select .....................................................................24 2.3.6. Output Latch Pins .................................................................................24 2.3.7. Offset and Gain Select ..........................................................................25 2.3.8. Filter Rate Select ..................................................................................25 2.4. Setting up the CSRs for a Measurement .........................................................27 2.5. Calibration ........................................................................................................30 2.5.1. Calibration Registers ............................................................................30 2.5.2. Performing Calibrations ........................................................................31 2.5.3. Self-calibration ......................................................................................31 2.5.4. System Calibration ................................................................................32 2.5.5. Calibration Tips .....................................................................................32 2.5.6. Limitations in Calibration Range ...........................................................33 2.6. Performing Conversions ..................................................................................33 2.6.1. Single Conversion Mode .......................................................................33 2.6.2. Continuous Conversion Mode ..............................................................34 2.6.3. Examples of Using CSRs to Perform Conversions and Calibrations ....35 2.7. Using Multiple ADCs Synchronously ...............................................................36 2.8. Conversion Output Coding ..............................................................................36 2.9. Digital Filter ......................................................................................................38 2.10. Clock Generator ...............................................................................................39 2.11. Power Supply Arrangements ...........................................................................39 2.12. Getting Started ................................................................................................43 2.13. PCB Layout .....................................................................................................43 3. PIN DESCRIPTIONS ...............................................................................................44 4. SPECIFICATION DEFINITIONS ...............................................................................46 5. ORDERING INFORMATION .....................................................................................47 6. ENVIRONMENTAL, MANUFACTURING, & HANDLING INFORMATION ..............47 7. PACKAGE DRAWINGS ...........................................................................................48 2 DS289F5