HC5520 データシートの表示（PDF） - Harris Semiconductor
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HC5520 Datasheet PDF : 20 Pages
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HC5520
∆VTR
ZL ∆IL
+
EG
-
A = 400
TIP
RTPS
∆ITS
RRGS
∆IRS
A = 400
RING
HC5520
∆IKZO
∆IRS ∆ITS
A2
-
+
∆IRX
2x∆IRX
∆IKZO
∆IRS ∆ITS
A1 ∆IKZO
+
-
R4W
RX
RN
ZKZO
+
VTX
-
+
VRX
-
FIGURE 2. SIMPLIFIED AC TRANSMISSION CIRCUIT
600Ω
TIP
RING
RTPS
100kΩ
RPT
50Ω
RPR
50Ω
RRGS
100kΩ
TIPSEN
RX
TIP
HC5520
RING TX4W
RINGSEN TX
RX
100kΩ
R4W
100kΩ
CVRX
0.47µF
0.47µF
CVTX
0.47µF
VRX
50kΩ
62pF
50kΩ
100kΩ
VTX
100kΩ
-
+
VOICE INPUT
AMPLIFIER
FIGURE 3. TRANSHYBRID BALANCE CIRCUIT WITH HIGH AND LOW FREQUENCY COMPENSATION
KZO Pin - The 2-wire impedance that is synthesized by the
HC5520 is a direct function of the network connected to this
pin (see equations). Parasitic capacitance and inductance
from the PC board layout and the external components is
magnified by the same K factor that is utilized to synthesize
the 2-wire impedance. Excessive parasitics can cause inser-
tion loss and return loss degradation, especially at higher
voice band frequencies. Good PC board layout techniques
and proper component selection can minimize these effects
to a negligible level.
RN Pin - This pin connects an external resistor to the input
of an internal buffer. The value of this resistor is user speci-
fied based upon the impedance desired at the 2-wire inter-
face (see equations). The value chosen must not have a
value greater than 7kΩ or the input voltage range of the
buffer may be exceeded during transients.
RDC Pin - An external resistor connected to VCC is required
at this pin to provide an accurate reference for the DC cur-
rents which feed the subscriber loop. PC board traces
should be made to have low resistance and should connect
directly to VCC.
CDC Pin - This pin provides a connection to the DC refer-
ence nodes that control the DC loop feed current. These
internal blocks are referenced to VEE and it is important that
the capacitor be referenced to VEE or else the PSRR perfor-
mance will be degraded.
CP Pin - Capacitor CP connects to this pin to create a low-
pass filter for the half-battery internal reference point. It is
important that this capacitor be referenced to BGND/AGND
to minimize the effect of noise injected into the subscriber
loop from the battery supply.
RPSG, RPST, RPSR, RPSB Pins - These pins are connected
to critical nodes inside the HC5519R3931 feedback control
loops. Parasitic capacitance should be minimized in order to
prevent oscillations.
RD, TB, TA Pins - The pins connect to the driver coils of the
Ring and Test relays and activate the relays by pulling down
the coil voltage to ground. The driver outputs are internally
clamped to VCC by diodes to prevent the inductive voltage
transient during relay turn-off from damaging the driver.
Relays attached to any voltage other than VCC will not func-
tion properly.
8
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