CS5460A Single Phase, Bi-directional Power/Energy IC Features Description Energy Data Linearity: 0.1% of Reading The CS5460A is a highly integrated power mea- surement solution which combines two over 1000:1 Dynamic Range. Analog-to-digital Converters (ADCs), high-speed On-Chip Functions: (Real) Energy, I V, power calculation functions, and a serial interface I and V , Energy-to-Pulse RMS RMS on a single chip. It is designed to accurately mea- Conversion sure and calculate: Real (True) Energy, Smart Auto-boot Mode from Serial Instantaneous Power, I , and V for single RMS RMS EEPROM Enables Use without MCU. phase 2- or 3-wire power metering applications. AC or DC System Calibration The CS5460A interfaces to a low-cost shunt resis- Mechanical Counter/Stepper Motor Driver tor or transformer to measure current, and to a resistive divider or potential transformer to mea- Meets Accuracy Spec for IEC 687/1036, JIS sure voltage. The CS5460A features a Typical Power Consumption <12 mW bi-directional serial interface for communication Interface Optimized for Shunt Sensor with a microcontroller and a pulse output engine for V vs. I Phase Compensation which the average pulse frequency is proportional Ground-Referenced Signals with Single to the real power. The CS5460A has on-chip func- Supply tionality to facilitate AC or DC system-level calibration. On-chip 2.5 V Reference (MAX 60 ppm/C drift) The Auto-boot feature allows the CS5460A to Simple Three-wire Digital Serial Interface function stand-alone and to initialize itself on sys- Watch Dog Timer tem power-up. In Auto-boot Mode, the CS5460A reads the calibration data and start-up instructions Power Supply Monitor from an external EEPROM. In this mode, the Power Supply Configurations CS5460A can operate without a microcontroller, in VA+ = +5 V VA- = 0 V VD+ = +3.3 V to +5 V order to lower the total bill-of-materials cost. VA+ RESET VD+ High Pass Watch Dog IIN+ PGA Filter Timer x10,x50 IIN- th 4 Order Digital MODE Filter Modulator Power CS Calculation SDI Engine Control / (Energy Serial SDO I*V Interface VIN+ SCLK I,V ) RMS RMS x10 nd VIN- 2 Order Digital INT Filter Energy-to- EDIR Modulator Pulse High Pass EOUT VREFIN x1 Converter Filter System Clock Calibration Voltage Power /K VREFOUT Clock Generator SRAM Reference Monitor VA- PFMON XIN XOUT CPUCLK DGND Cirrus Logic, Inc. Copyright Cirrus Logic, Inc. 2011 APR 11 (All Rights Reserved) CS5460A TABLE OF CONTENTS 1. CHARACTERISTICS & SPECIFICATIONS ............................................................................. 5 ANALOG CHARACTERISTICS................................................................................................ 5 VREFOUT REFERENCE OUTPUT VOLTAGE........................................................................ 7 5V DIGITAL CHARACTERISTICS............................................................................................ 7 3.3 V DIGITAL CHARACTERISTICS........................................................................................ 8 ABSOLUTE MAXIMUM RATINGS ........................................................................................... 8 SWITCHING CHARACTERISTICS .......................................................................................... 9 2. OVERVIEW ............................................................................................................................. 12 2.1 Theory of Operation ......................................................................................................... 12 2.1.1 DS Modulators ................................................................................................... 12 2.1.2 High-rate Digital Low-pass Filters ....................................................................... 12 2.1.3 Digital Compensation Filters ............................................................................... 12 2.1.4 Digital High-pass Filters ......................................................................................12 2.1.5 Overall Filter Response ....................................................................................... 13 2.1.6 Gain and DC Offset Adjustment .......................................................................... 13 2.1.7 Real Energy and RMS Computations ................................................................. 13 2.2 Performing Measurements ............................................................................................... 13 2.2.1 CS5460A Linearity Performance ......................................................................... 15 2.2.2 Single Computation Cycle (C=0) ......................................................................... 15 2.2.3 Continuous Computation Cycles (C=1) ............................................................... 16 2.3 Basic Application Circuit Configurations .......................................................................... 16 3. FUNCTIONAL DESCRIPTION ............................................................................................... 21 3.1 Pulse-Rate Output ........................................................................................................... 21 3.2 Pulse Output for Normal Format, Stepper Motor Format and Mechanical Counter Format 22 3.2.1 Normal Format .................................................................................................... 22 3.2.2 Mechanical Counter Format ................................................................................ 23 3.2.3 Stepper Motor Format ......................................................................................... 23 3.3 Auto-boot Mode Using EEPROM ..................................................................................... 24 3.3.1 Auto-boot Configuration ...................................................................................... 24 3.3.2 Auto-boot Data for EEPROM .............................................................................. 25 3.3.3 Application Note AN225 ...................................................................................... 26 3.4 Interrupt and Watchdog Timer ......................................................................................... 26 3.4.1 Interrupt ............................................................................................................... 26 3.4.1.1 Clearing the Status Register ............................................................... 26 3.4.1.2 Typical use of the INT pin ................................................................... 26 3.4.1.3 INT Active State .................................................................................. 26 3.4.1.4 Exceptions ........................................................................................... 26 3.4.2 Watch Dog Timer ................................................................................................ 26 3.5 Oscillator Characteristics .................................................................................................27 3.6 Analog Inputs ................................................................................................................... 27 3.7 Voltage Reference ........................................................................................................... 27 3.8 Calibration ........................................................................................................................ 27 3.8.1 Overview of Calibration Process ......................................................................... 27 3.8.2 The Calibration Registers .................................................................................... 28 3.8.3 Calibration Sequence .......................................................................................... 28 3.8.4 Calibration Signal Input Level ............................................................................. 29 3.8.5 Calibration Signal Frequency .............................................................................. 29 3.8.6 Input Configurations for Calibrations ................................................................... 29 3.8.7 Description of Calibration Algorithms .................................................................. 30 3.8.7.1 AC Offset Calibration Sequence ......................................................... 30 3.8.7.2 DC Offset Calibration Sequence ......................................................... 31 3.8.7.3 AC Gain Calibration Sequence ........................................................... 31 2 DS487F5