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ADS7883_08 Datasheet, PDF (11/17 Pages) Texas Instruments – 12-BIT, 3-MSPS, MICROPOWER, MINIATURE SAR ANALOG-TO-DIGITAL CONVERTER
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ADS7883
www.ti.com ....................................................................................................................................................................................................... SLAS594 – JULY 2008
APPLICATION INFORMATION
VDD
50 W
IN
20 W
GND
50 W
20 pF
7 pF
Figure 24. Typical Equivalent Sampling Circuit
Driving the VIN and VDD Pins
The VIN input to the ADS7883 should be driven with a low impedance source. In most cases additional buffers
are not required. In cases where the source impedance exceeds 200 Ω, using a buffer would help achieve the
rated performance of the converter. The THS4031 is a good choice for the driver amplifier buffer.
The reference voltage for the ADS7883 A/D converter is derived from the supply voltage internally. The device
offers limited low-pass filtering functionality on-chip. The supply to these converters should be driven with a low
impedance source and should be decoupled to the ground. A 1-µF storage capacitor and a 10-nF decoupling
capacitor should be placed close to the device. Wide, low impedance traces should be used to connect the
capacitor to the pins of the device. The ADS7883 draws very little current from the supply lines. The supply line
can be driven by either:
• Directly from the system supply.
• A reference output from a low drift and low drop out reference voltage generator like the REF5030 or
REF5050. The ADS7883 can operate with a wide range of supply voltages. The actual choice of the
reference voltage generator depends upon the system. Figure 26 shows one possible application circuit.
• A low-pass filtered version of the system supply followed by a buffer like the zero-drift OPA735 can also be
used in cases where the system power supply is noisy. Care should be taken to ensure that the voltage at the
VDD input does not exceed 7 V (especially during power up) to avoid damage to the converter. This can be
done easily using single supply CMOS amplifiers like the OPA735. Figure 27 shows one possible application
circuit.
VDD
1 mF 10 nF
VDD
VIN
GND
CS
SDO
SCLK
Figure 25. Supply/Reference Decoupling Capacitors
5V/7V
1mF
REF5030/REF5050
IN
OUT
GND
3V/5V
1 mF 10 nF
VDD
VIN
GND
CS
SDO
SCLK
Figure 26. Using the REF5030/REF5050 Reference
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): ADS7883
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