xrt5897 Exar Corporation, xrt5897 Datasheet - Page 14

• Manufacturer Part Number: xrt5897
• Description: Xrt5897 -seven-channel E1 Line Interface
• Manufacturer: Exar Corporation

Transmitters
This device contains four identical ITU G.703 compliant
transmitters. The output stage of each transmitter is a
differential voltage driver. External resistors need to be
connected to the primary of output transformer. This is
necessary to maintain an accurate source impedance
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
XRT5897
Rev. 1.11
V = 100%
50%
0%
Note: V corresponds to the nominal peak value
10%
10%
10%
10%
Figure 4. CCITT G.703 Pulse Template
20%
20%
14
20%
(244 + 25)
(244 -- 50)
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 XRT5897 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.
(244 + 244)
(244 -- 25)
194 ns
269 ns
244 ns
219 ns
488 ns
10%
10%
Nominal pulse