AD7470:  10-Bit, 2.7 V to 5.25 V, 1.75 MSPS Low Power ADC

The AD7470/AD7472 are 10-bit/12-bit high speed, low power, successive-approximation ADCs. The parts operate from a single 2.7 V to 5.25 V power supply and feature throughput rates up to 1.5 MSPS for the 12-bit AD7472 and up to 1.75 MSPS for the 10-bit AD7470. The parts contain a low-noise, wide bandwidth track/hold amplifier which can handle input frequencies in excess of 20 MHz.

The conversion process and data acquisition are controlled using standard control inputs, allowing easy interfacing to microprocessors or DSPs. The input signal is sampled on the falling edge of CONVST, and conversion is also initiated at this point. BUSY goes high at the start of conversion and goes low 531.66 ns after falling edge of CONVST (AD7472 with a clock frequency of 26 MHz) to indicate that the conversion is complete. There are no pipeline delays associated with the parts. The conversion result is accessed via standard CS and RD signals over a high speed parallel interface.

The AD7470/AD7472 use advanced design techniques to achieve very low power dissipation at high throughput rates. With 3 V supplies and 1.5 MSPS throughput rates, the AD7470 typically consumes, on average, just 1.1 mA. With 5 V supplies and 1.75 MSPS, the average current consumption is typically 1.6 mA. The part also offers flexible power/throughput rate management. Operating the AD7470 with 3 V supplies and 500 kSPS throughput reduces the current consumption to 713 μA. At 5 V supplies and 500 kSPS, the part consumes 944 μA.

It is also possible to operate the parts in an auto sleep mode, where the part wakes up to do a conversion and automatically enters sleep mode at the end of conversion. This method allows very low power dissipation numbers at lower throughput rates. In this mode, the AD7472 can be operated with 3 V supplies at 100 kSPS, and consume an average current of just 124 μA. At 5 V supplies and 100 kSPS, the average current consumption is 171 μA.

The analog input range for the part is 0 V to REF IN. The 2.5 V reference is applied externally to the REF IN pin. The conversion rate is determined by the externally-applied clock.

Product Highlights

1. High Throughput with Low Power Consumption. The AD7470 offers 1.75 MSPS throughput and the AD7472 offers 1.5 MSPS throughput rates with 4 mW power consumption.
2. Flexible Power/Throughput Rate Management. The conversion rate is determined by an externally-applied clock allowing the power to be reduced as the conversion rate is reduced. The part also features an auto sleep mode to maximize power efficiency at lower throughput rates.
3. No Pipeline Delay. The part features a standard successive approximation ADC with accurate control of the sampling instant via a CONVST input and once off conversion control.