UPD9903 Datasheet, PDF (7/28 Pages) NEC – UPD9903 ANALOG SUBSCRIBER LINE LSI DIGITAL CODEC

µPD9903
2. USE CAUTIONS
(1) Combined characteristics of the µPC9903 and µPD7073
• The µPD9903 is designed to be used in combination with the µPC7073. Therefore, the first half of the electrical
specifications described below are ratings for the µPD9903 as a discrete unit while the second half are
combined ratings with the µPC7073.
• Subscriber circuit constants that are determined by factors such as termination impedance are configured to
enable setting by external order parameters. Consequently, input of an order that is not suitable for the target
impedance may result in failure to obtain the required characteristics.
(2) Absolute maximum ratings
Application of voltage or current in excess of the absolute maximum ratings may result in damage. Be
especially cautious about surges, etc.
(3) Load of by-pass capacitor
Because the µPC7073 and µPD9903 use several internal high-frequency operational amplifiers, high power
supply impedance can cause instability in these internal operational amplifiers (such as oscillation). To
suppress such instability and eliminate power supply noise, connect by-pass capacitors (CACOM = approximate
0.1 µF) having superior high frequency characteristics as close as possible to the µPC7073’s power supply
pins (VBB and VCC) and the µPD9903’s power supply pins (AVDD and DVDD).
(4) Addition of ACOM pin connection capacitor
The voltage of the ACOM pin between the µPC7073 and µPD9903 is the reference voltage of the signal
source between the µPC9903 and µPC7073. Superposing of noise on this pin may have adverse effects
on transmission characteristics. Therefore, make the wires between the ACOM pins of the two LSIs as short
as possible, and connect capacitors (CACOM = approximate 0.1 µF) having superior high frequency
characteristics as close as possible to the pins.
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