Document
Preliminary Technical Data
FEATURES
12 bit SAR ADC 8 single-ended inputs Channel sequencer functionality Analog Input Range 0 to 2.5V 12-bit temperature-to-digital converter Temperature sensor accuracy of ±2°C typical Temperature range: −40°C to +125°C Specified for VDD of 2.8 V to 3.6V Logic Voltage VDRIVE = 1.65V to 3.6V Power-down current : <10 µA Internal 2.5V Reference I2C-compatible serial interface supports standard & fast modes 20-lead LFCSP
8-Channel, I2C, 12-Bit SAR ADC with Temperature Sensor AD7291
Functional Block Diagram
Figure 1.
GENERAL DESCRIPTION
The AD7291 is a 12-bit, high speed, low power, 8-channel, successive approximation ADC with an internal temperature sensor. The part operates from a single 3.3V power supply and features an I2C®-compatible interface. The track-and-hold amplifier which can handle input frequencies of up to 70MHz, and a multiplexer allows samples from eight channels. Each AD7291 provides a 2-wire serial interface compatible with www.DataSheet4U.com I2C interfaces. The AD7291 offers a programmable sequencer, which enables the selection of a pre-programmable sequence of channels for conversion. The device has an on-chip 2.5 V reference that can be disabled to allow the use of an external reference. The AD7291 includes a high accuracy band-gap temperature sensor, which is monitored and digitized by the12-bit ADC to give a resolution of 0.25°C. The AD7291 uses advanced design techniques to achieve very low power dissipation at high throughput rates. The part also offers flexible power/throughput rate management options and is offered in a 20 lead LFCSP package
PRODUCT HIGHLIGHTS
1. Ideally suited to monitoring system variables in a variety of systems including telecommunications, process and industrial control I2C-compatible serial interface. Standard and fast modes. Eight Single-Ended Inputs with a Channel Sequencer. A consecutive sequence of channels can be selected on which the ADC cycles and converts. Integrated temperature sensor with 0.25°C resolution.
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Table 1. AD7298 and Related Products
Device AD7298 AD7291 Resolution 12-Bit 12-Bit Interface SPI I2 C Features 8 Channel ADC & Temp Sensor 8 Channel ADC & Temp Sensor
Rev. PrC
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AD7291 SPECIFICATIONS
AD7291 SPECIFICATIONS
Preliminary Technical Data
VDD = 2.8V to 3.6V; VDRIVE = 1.65 V to 3.6 V; fSCLK = 400KHz, fast SCLK mode; VREF = 2.5 V internal/external; TA = −40°C to +125°C, unless otherwise noted. Table 2.
Parameter DYNAMIC PERFORMANCE Signal-to-Noise Ratio (SNR) 1 Signal-to-Noise (+ Distortion) Ratio (SINAD)1 Total Harmonic Distortion (THD)1 Spurious-Free Dynamic Range (SFDR)1 Intermodulation Distortion (IMD)1 Second-Order Terms Third-Order Terms Channel-to-Channel Isolation1 Full Power Bandwidth2 DC ACCURACY Resolution Integral Nonlinearity (INL)1 Differential Nonlinearity (DNL)1 Offset Error Offset Error Matching Offset Temperature Drift Gain Error Gain Error Matching Gain Temperature Drift ANALOG INPUT Input Voltage Ranges www.DataSheet4U.com DC Leakage Current Input Capacitance2 Input Impedance2 REFERENCE INPUT/OUTPUT Reference Output Voltage3 Long-Term Stability Output Voltage Hysteresis1 Reference Input Voltage Range4 DC Leakage Current Input Capacitance VREF Output Impedance Reference Temperature Coefficient VREF Noise2 Min 70 70 Typ 71 71 −84 −85 −88 −88 −100 TBD TBD 12 ±0.5 ±0.5 ±1 ±0.5 4 ±1 ±0.5 0.5 0 ±0.01 32 TBD 2.4875 2.5 150 50 2.0 ±0.01 TBD TBD 6 60 2.5 ±1 2.512 5 ±1 ±0.99 ±6 ±1 ±2 ±1 Max Unit dB dB dB dB fA = 5.4 kHz, fB = 4.6 kHz dB dB dB MHz MHz Bits LSB LSB LSB LSB ppm/°C LSB LSB ppm/°C V µA pF kΩ V ppm ppm V µA pF Ω ppm/°C µV rms ±0.5% maximum @ 25°C For 1000 hours Test Conditions/Comments fIN = 10 kHz sine wave
78 80
@ 3 dB @ 0.1 dB
Guaranteed no missed codes to 12 bits
VREF ±1
During Acquisition Outside Acquisition
External reference applied to Pin VREF
25
Bandwidth = TBD kHz
Rev. PrC | Page 2 of 21
Preliminary Technical Data
Parameter LOGIC INPUTS (SDA, SCL) Input High Voltage, VINH Input Low Voltage, VINL Input Current, IIN Input Capacitance, CIN2 Input Hysteresis, VHYST LOGIC OUTPUTS (OPEN DRAIN) Output Low Voltage, VOL Floating State Leakage Current Floating State Output Capacitance2 Output Coding TEMPERATURE SENSOR—INTERNAL Operating Range Accuracy Resolution CONVERSION RATE Conversion Time Autocycle Update Rate Through.