ADS-230 Datel, Inc., ADS-230 Datasheet - Page 8

• Manufacturer Part Number: ADS-230
• Description: Sampling A/D Converters
• Manufacturer: Datel, Inc.

ADS-230/ADS-231
Power Supply
The ADS-230 and ADS-231 are designed to operate off a
There are two analog pins AV
There are two analog ground pins (AGND), three digital
single +5V supply. To guarantee proper operation of the
converters, only one power supply should be used. If
separate analog and digital supplies are used, then the
converter must be powered up with the analog supply. The
absolute maximum ratings states that all inputs must be
between GND –300mV and VS +300mV. When the
converter power supply is turned off the maximum input
becomes ±300mV, which in turn requires that the devices
connected to the converter have power removed before
power to the converter is removed.
DV
digital sections of the circuit. Both AV
bypassed to ground with 0.1µF ceramic capacitors. At least
one of the AV
tantalum capacitor. The DV
a 0.1µF ceramic capacitor in parallel with a 10µF tantalum
capacitor. All bypass capacitor should be located as close
to the converter as possible.
ground pins for the control inputs (DGNDC), and one digital
ground pin for the data output lines (DGNDD). Separating
the analog section from the digital sections reduces digital
S
. This allows for separate bypassing of the analog and
S
pins should be bypassed with a 10µF
S
input should be bypassed with
S
and one digital supply pin
S
pins should be
8
S/H Input
These large current spikes will couple back to the analog
The clock source driving the S/H input must be free of jitter.
interference in the analog circuitry thereby improving the
dynamic performance of the converter. When driving a high
capacitance digital data bus buffering the output data lines
maybe necessary to minimize the DV
spikes generated each conversion to charge the data bus
capacitance.
circuitry increasing the converter noise level. Separating
the digital outputs from the digital inputs reduces the
possibility of ground bounce from the data lines causing
jitter on the S/H input. The digital ground planes should be
tied together at the digital ground pins. The analog ground
plane should be tied to the DGNDD ground plane at the
ground return strap for the power supply.
For best performance, a crystal oscillator is recommended.
For the ADS-230 and ADS-231, a 1.0 and 1.5Mhz square
wave will provide a good signal for the respective S/H
inputs. In both cases, as long as the duty cycle is near
50%, the S/H pulse widths fall under the maximum allowed.
When operating the ADS-230 below 910kHz or the ADS-
231 below 1.25MHz, the S/H pulse widths must be less
than half the respective sample periods.
®
S
and DGND current
®