DESCRIPCIÓN GENERAL

The AD7888 is a high speed, low power, 12-bit ADC that operates from a single 2.7 V to 5.25V power supply. The AD7888 is capable of a 125 kSPS throughput rate. The input track-andhold acquires a signal in 500 ns and features a single-ended sampling scheme. The AD7888 contains eight single-ended analog inputs, AIN1 through AIN8. The analog input on each of these channels is from 0 to VREF. The part is capable of converting full power signals up to 2.5 MHz.
The AD7888 features an on-chip 2.5 V reference that can be used as the reference source for the A/D converter. The REF IN/REF OUT pin allows the user access to this reference. Alternatively, this pin can be overdriven to provide an external reference voltage for the AD7888. The voltage range for this external reference is from 1.2 V to VDD.
CMOS construction ensures low power dissipation of typically 2 mW for normal operation and 3 µW in power-down mode.The part is available in a 16-lead narrow body small outline (SOIC) and a 16-lead thin shrink small outline (TSSOP) package.

 

CARACTERÍSTICAS

Specified for VDD of 2.7 V to 5.25 V
Flexible Power/Throughput Rate Management
Shutdown Mode: 1 A Max
Eight Single-Ended Inputs
Serial Interface: SPI™/QSPI™/MICROWIRE™/DSP Compatible
16-Lead Narrow SOIC and TSSOP Packages

 

APLICACIONES

Battery-Powered Systems (Personal Digital Assistants, Medical Instruments, Mobile Communications)
Instrumentation and Control Systems
High-Speed Modems

 

PRODUCTOS DESTACADOS

1. Smallest 12-bit 8-channel ADC; 16-lead TSSOP is the same area as an 8-lead SOIC and less than half the height.
2. Lowest Power 12-bit 8-channel ADC.
3. Flexible power management options including automatic power-down after conversion.
4. Analog input range from 0 V to VREF (VDD).
5. Versatile serial I/O port (SPI/QSPI/MICROWIRE/DSP Compatible).

 

TERMINOLOGÍA

Integral Nonlinearity

This is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale, a point 1/2 LSB below the first code transition, and full scale, a point 1/2 LSB above the last code transition.

Channel-to-Channel Isolation

Channel-to-channel isolation is a measure of the level of crosstalk between channels. It is measured by applying a full-scale 25 kHz sine wave signal to all nonselected input channels and determining how much that signal is attenuated in the selected channel.
The figure given is the worst case across all four or eight channels for the AD7888.

PSR (Power Supply Rejection)

Variations in power supply will affect the full-scale transition, but not the converter’s linearity. Power supply rejection is the maximum change in the full-scale transition point due to a change in power-supply voltage from the nominal value.

CIRCUIT INFORMATION

The AD7888 is a fast, low power, 12-bit, single supply, 8-channel A/D converter. The part can be operated from 3 V (2.7 V to 3.6 V) supply or from 5 V (4.75 V to 5.25 V) supply. When operated from either a 5 V supply or a 3 V supply, the AD7888 is capable of throughput rates of 125 kSPS when provided with a 2 MHz clock.
The AD7888 provides the user with an 8-channel multiplexer, on-chip track/hold, A/D converter, reference and serial interface housed in a tiny 16-lead TSSOP package, which offers the user considerable space saving advantages over alternative solutions. The serial clock input accesses data from the part and also provides the clock source for the successive-approximation A/D converter. The analog input range is 0 to VREF (where the externally-applied VREF can be between 1.2 V and VDD). The 8-channel multiplexer is controlled by the part’s Control Register. This Control Register also allows the user to power-off the internal reference and to determine the Modes of Operation.