UPC7073 查看數據表（PDF） - NEC => Renesas Technology
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UPC7073 Datasheet PDF : 20 Pages
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µPC7073
2. USE CAUTIONS
(1) Combined characteristics of µPC7073 and µPD9903
• The µPC7073 is designed to be used in combination with the µPD9903. Therefore, first half of the electrical
characteristics described below are ratings for the µPC7073 as a discrete unit while the second half are
combined ratings that include the µPD9903.
• 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 (such as oscillation) in these internal operational amplifiers. To
suppress such instability and eliminate power supply noise, connect by-pass capacitors (CACOM = approx.
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 signal source reference voltage
for the µPC7073. Superposition of noise on this pin may have adverse effects on transmission character-
istics. Therefore, make the wires between the ACOM pin and the two LSIs as short as possible, and connect
capacitors (CACOM = approx. 0.1 µF) having superior high frequency characteristics as close as possible to
the pins.
(5) Overcurrent prevention measures
Due to its structure, power to the µPC7073 must first be supplied to a low-voltage potential (VBB).
Accordingly, if power is supplied first to a power supply pin other than VBB, an overcurrent will flow within
the µPC7073 (an overcurrent will not flow if power is input to all power supply pins).
Therefore, if feeding to a power supply pin other than VBB first, connect an external diode and limiting resistor
(rated at several Ω) in the directions described below.
• Reverse-bias direction between VBB pin and VCC pin.
• Reverse-bias direction between VBB pin and GND.
• Reverse-bias direction between VCC pin and GND.
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