MB40178 datasheet(18/21 Pages) FUJITSU

18 / 21 page

MB40168/MB40178

s NOTES ON PCB LAYOUT

Power Supply Lines

The device’s power supply lines (VCCA, VCCD, AGND and DGND) should be laid out as analog lines and should

be separated in so far as possible from other digital lines in order to reduce noise. Also the track widths of these

lines should be as wide as possible to reduce parasitic impedance.

Coupling Capacitors

The device’s power supply lines VCCA and VCCD and the reference voltage pins VRIN, VREF, VRB, and VRT should

be decoupled to analog ground by means of approx. 1

µF capacitors which should be placed as close as possible

to these pins.

Digital Output Load

The load at the digital outputs should be kept as low as possible to prevent noise in the power supply lines

caused by digital output switching. If, due to long wiring, the load becomes large then a buffer with small input

capacitance should be inserted to reduce load capacitance.

s OTHER NOTES ON OPERATION

When using the D/A converter with its VRIN pin connected to the VREF pin, the A/D converter’s VRB pin must also

be connected to the VREF because otherwise the internal reference voltage generation circuitry cannot output 3 V.

When using the D/A converter with 8 bit resolution the DD9 (LSB) pin should be grounded.

MB40178 Datasheet(PDF) 18 Page - fujitsu semiconductor