DS26503L Maxim Integrated Products, DS26503L Datasheet - Page 78

• Manufacturer Part Number: DS26503L
• Description: Timers & Support Products E1-T1-J1 BITS Elemen t T1-E1-J1 BITS Elem
• Manufacturer: Maxim Integrated Products
• Type: Clock Recoveryr

Specifications of DS26503L

• Supply Voltage (max): 3.46 V
• Supply Voltage (min): 3.13 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Supply Current: 85 mA
• Package / Case: LQFP-64

DS26503 T1/E1/J1 BITS Element
13.1 LIU Operation
The LIU interfaces the T1, E1, and 6312kHz signals to the various types of network media through
coupling transformers. The LIU transmit and receive functions are independent. For example, the receiver
can be in T1 mode while the transmitter is in E1 mode. The 6312kHz transmission is an exception to the
other modes. For transmission, 6312kHz is only available as a 0 to 3.3V signal on the TCLKO pin. It is
not output to the TTIP and TRING pins for coupling to twisted pair. Because the G.703 specifications of
the transmit pulse shape for Japanese 6312kHz are unclear, the user can externally filter this signal to
generate a sine wave type of signal. However, on the receive side, 6312kHz can be input through the
receive transformer to the RTIP and RRING pins.
13.2 LIU Receiver
The analog AMI/HDB3 E1 waveform or AMI/B8ZS T1 waveform is transformer-coupled into the RTIP
and RRING pins of the DS26503. The user has the option to use internal termination, software selectable
for 75/100/110/120Ω application, or external termination. The LIU recovers clock and data from the
analog signal and passes it through the jitter attenuation mux. (Note: The jitter attenuator is only available
in T1 or E1 mode.) The DS26503 contains an active filter that reconstructs the analog-received signal for
the nonlinear losses that occur in long-haul T1 and E1 transmission. The receiver is configurable for
various T1 and E1 monitor applications. The device has a usable receive sensitivity of 0dB to –43dB for
E1 and 0dB to –36dB for T1, which allows the device to operate on 0.63mm (22AWG) cables up to
2.5km (E1) and 6000ft (T1) in length.
The DS26503’s LIU is designed to be fully software selectable for E1 and T1 without the need to change
any external resistors for the receive-side. The receiver will allow the user to configure the DS26503 for
75Ω, 100Ω, 110Ω, or 120Ω receive termination by setting the RT0(LIC4.0), RT1(LIC4.1), and
RT2(LIC4.2). When using the internal termination feature, the resistors labeled R in
Figure 13-4
should
be 60Ω each. If external termination is used, RT0, RT1, and RT2 should be set to zero and the resistors
labeled R in
Figure 13-4
will need to be 37.5Ω, 50Ω, 55Ω, or 60Ω each, depending on the required
termination.
There are two ranges of receive sensitivity for T1 and E1, which is selectable by the user. The EGL bit of
LIC1 (LIC1.4) selects the full or limited sensitivity.
Normally, the clock that is output at the RCLK pin is the recovered clock from the waveform presented at
the RTIP and RRING inputs. If the jitter attenuator 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 over-sampled digital clock recovery circuitry. See the
Receive AC Timing Characteristics section for more details. When no signal is present at RTIP and
RRING, a receive loss of signal (RLOS) condition will occur and the signal at RCLK will be derived
from the scaled signal present on the MCLK pin.
13.2.1 Receive Level Indicator
The DS26503 will report the signal strength at RTIP and RRING in 2.5dB increments via RL3-RL0
located in the Information Register 1 (INFO1). This feature is helpful when trouble shooting line
performance problems.
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