Le7942B
Data Sheet
Table 2. User-Programmable Components
ZRX is connected from VRX to the RSN. ZT is defined above,
and G42L is the desired receive gain.
ZL
500ZT
------------ -------------------------------------------------
ZRX
=
•
G42L ZT + 250(ZL + 2RF)
RDC1, RDC2, and CDC form the network connected to the
RDC pin. RDC1 and RDC2 are approximately equal. ILOOP is
the desired loop current in the constant-current region.
625
RDC1 + RDC2 = -------------
ILOOP
RDC1 + RDC2
-------------------------------
RDC1 RDC2
CDC = 1.5 ms •
RD and CD form a network connected from RD to either
ground or –5 V, and IT is the threshold current between on
hook and off hook.
365
RD = -------- If RD is connected to ground.
IT
1825
RD = ----------- If RD is connected to -5V.
IT
0.5 ms
CD = ----------------
RD
C
CAS is the regulator filter capacitor, and fc is the desired filter
1
CCAS = -----------------------------
cut-off frequency.
3.4 • 105πfc
Note:
*RFUSE = 20 – 50 Ω, user selectable.
12
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
