DS26521LN+ Maxim Integrated Products, DS26521LN+ Datasheet - Page 73

• Manufacturer Part Number: DS26521LN+
• Description: IC TXRX T1/E1/J1 64-LQFP
• Manufacturer: Maxim Integrated Products
• Type: Line Interface Units (LIUs)r

Specifications of DS26521LN+

• Number Of Drivers/receivers: 1/1
• Protocol: T1/E1/J1
• Voltage - Supply: 3.135 V ~ 3.465 V
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.11.3 Receiver
The DS26521 contains identical receivers. Both receivers are designed to be fully software-selectable for E1, T1,
and J1 without the need to change any external resistors. The device couples to the receive E1 or T1 twisted pair
(or coaxial cable in 75Ω E1 applications) via a 1:1 or 2:1 transformer. See
Receive termination and sensitivity are user configurable. Receive termination is configurable for 75Ω, 100Ω,
110Ω, or 120Ω termination by setting the appropriate RIMPM[1:0] bits (LRISMR). When using the internal
termination feature, the resistors labeled Rr in
the resistors need to be 37.5Ω, 50Ω, or 60Ω each depending on the line impedance. Receive sensitivity is
configurable by setting the appropriate RSMS[1:0] bits (LRISMR).
The DS26521 uses a digital clock recovery system. The resultant E1, T1, or J1 clock derived from MCLK is
multiplied by 16 via an internal PLL and fed to the clock recovery system. The clock recovery system uses the
clock from the PLL circuit to form a 16 times oversampler, which is used to recover the clock and data. This
oversampling technique offers outstanding performance to meet jitter tolerance specifications shown in
Figure
Normally, the clock that is output at the RCLK pin is the recovered clock from the E1 AMI/HDB3 or T1 AMI/B8ZS
waveform presented at the RTIP and RRING inputs. If the jitter attenuator (LTRCR) is placed in the receive path
(as is the case in most applications), the jitter attenuator restores the RCLK to an approximate 50% duty cycle. If
the jitter attenuator is either placed in the transmit path or is disabled, the RCLK output can exhibit slightly shorter
high cycles of the clock. This is due to the highly oversampled digital clock recovery circuitry. See
more details. When no signal is present at RTIP and RRING, a receive carrier loss (RCL) condition occurs and the
RCLK is derived from the JACLK source.
8.11.3.1
The DS26521 reports the signal strength at RTIP and RRING in approximately 2.5dB increments via RSL3:RSL0
located in the LIU Receive Signal Level register (LRSL). This feature is helpful when trouble shooting line
performance problems.
8.11.3.2
The DS26521 can receive a 2.048MHz square-wave synchronization clock as specified in Section 10 of ITU-T
G.703. To use this mode, set the receive G.703 clock-enable bit RG703 (LRISMR.7) found in the LIU Receive
Impedance and Sensitivity Monitor register (LRISMR).
8.11.3.3
The receive equalizer is equipped with a monitor mode function that is used to overcome the signal attenuation
caused by the resistive bridge used in monitoring applications. This function allows for a resistive gain of up to
32dB, along with cable attenuation of 12dB to 30dB as shown in the LIU Receive Impedance and Sensitivity
Monitor register (LRISMR).
8-21.
Receive Level Indicator
Receive G.703 Section 10 Synchronization Signal
Receiver Monitor Mode
Figure 8-17
73 of 258
should be 60Ω each. If external termination is required,
DS26521 Single T1/E1/J1 Transceiver
Table 8-32
for transformer details.
Table 12-3
for