XRT5894 Datasheet, PDF (12/19 Pages) Exar Corporation – Four-Channel E1 Line Interface (3.3V or 5.0V)

XRT5894
that ensures compliance to ETSI 300 166 return loss
requirement.
TTL compatible dual rail transmit data signals are
supplied to TXPOS and TXNEG inputs. The transmitter
differential outputs TTIP and TRING are connected to the
output transformer primary through series 9.1W resistors.
All the four transmitters can be operated in two distinct
modes of operation referred to as “clocked” or “clockless”
modes. The operational mode is selected automatically
based on the signal provided to TXCLK input. If a clock is
present at this pin, the transmitter detects its presence
and operates in the clocked mode. In this mode, the
transmit input should be supplied with full-width NRZ
pulses. If a clock is not present at the TXCLK input (pin is
left open), the part operates in the clockless mode. In this
mode, RZ data should be supplied to the device. Each
transmit channel of XRT5894 has a duty cycle correction
circuitry. This enables the device to produce output
bipolar pulses fully compliant with G.703 despite having
TXCLK signal with 30% to 70% duty cycle.
V = 100%
20%
10%
10%
20%
269 ns
(244 + 25)
194 ns
(244 -- 50)
Nominal pulse
50%
244 ns
219 ns
(244 -- 25)
10%
0%
10%
20%
10%
10%
488 ns
(244 + 244)
Note: V corresponds to the nominal peak value
Figure 4. CCITT G.703 Pulse Template
Rev. 1.10
12