AD7991 Datasheet

• 12-bit ADCs with fast conversion time: 1 μs typical
• 4 analog input channels/3 analog input channels with reference input
• Specified for V_DD of 2.7 V to 5.5 V
• Sequencer operation
• Temperature range: −40°C to +125°C
• I²C-compatible serial interface supports standard, fast, and high speed modes
• 2 versions allow 2 I²C addresses
• Low power consumption
  • Shutdown mode: 1 μA maximum
• 8-lead SOT-23 package
• Qualified for automotive applications

• System monitoring
• Battery-powered systems
• Data acquisition
• Medical instruments

The AD7991 are 12-bit, low power, successive approximation ADCs with an I²C^®-compatible interface. Each part operates from a single 2.7 V to 5.5 V power supply and features a 1 μs conversion time. The track-and-hold amplifier allows each part to handle input frequencies of up to 14 MHz, and a multiplexer allows taking samples from four channels.

Each AD7991 provides a 2-wire serial interface compatible with I²C interfaces. The AD7991 come in two versions and each version has an individual I²C address. This allows two of the same devices to be connected to the same I²C bus. Both versions support standard, fast, and high speed I²C interface modes.

The AD7991 normally remain in a shutdown state, powering up only for conversions. The conversion process is controlled by a command mode, during which each I²C read operation initiates a conversion and returns the result over the I²C bus.

When four channels are used as analog inputs, the reference for the part is taken from V_DD; this allows the widest dynamic input range to the ADC. Therefore, the analog input range to the ADC is 0 V to V_DD;. An external reference, applied through the V_IN3/V_REF input, can also be used with this part.