DS21552L+ Maxim Integrated Products, DS21552L+ Datasheet - Page 90

• Manufacturer Part Number: DS21552L+
• Description: IC TXRX T1 1-CHIP 5V 100-LQFP
• Manufacturer: Maxim Integrated Products

Specifications of DS21552L+

• Function: Single-Chip Transceiver
• Interface: E1, HDLC, J1, T1
• Number Of Circuits: 1
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 75mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 100-LQFP
• Includes: DSX-1 and CSU Line Build-Out Generator, HDLC Controller, In-Band Loop Code Generator and Detector
• Product: Framer
• Number Of Transceivers: 1
• Data Rate: 64 Kbps
• Supply Voltage (max): 3.465 V
• Supply Voltage (min): 3.135 V
• Supply Current (max): 75 mA (Typ)
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Ic Interface Type: Parallel, Serial
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: 0°C To +70°C
• Digital Ic Case Style: LQFP
• No. Of Pins: 100
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

DS21352/DS21552
16.4 PROTECTED INTERFACES
In certain applications, such as connecting to the PSTN, it is required that the network interface be
protected from and resistant to certain electrical conditions. These conditions are divided into two
categories, surge and power line cross. A typical cause of surge is lightening strike. Power line cross
refers to accidental contact with high voltage power wiring. For protection against surges, additional
components and PCB layout considerations are required to reroute and dissipate this energy. In a surge
event, the network interface must not be damaged and continue to work after the event. In the event of a
power line contact, components such as fuses or PTCs that can “open” the circuit are required to prevent
the possibility of a fire caused by overheating the transformer. The circuit examples in this data sheet are
for “Secondary Over Voltage Protection” schemes for the line terminating equipment. Primary protection
is typically provided by the network service provide and is external to the equipment.
Figure 16-6 shows an example circuit for the 5 volt device and Figure 16-7 is an example for the 3.3
device. In both examples, fuses are used to provide protection against power line cross. 470 ohm input
resistors on the receive pair, a transient suppresser and a diode bridge on the transmit pair provide surge
protection. Resistors R1 – R4 provide surge protection for the fuse. Careful selection of the transformer
will allow the use of a fuse that requires no additional surge protection such as the circuit shown in Figure
16-7. The circuit shown in Figure 16-7 is required for 3.3 volt operation since additional resistance in the
transmit pair cannot be tolerated. For more information on line interface design, consult the T1 Line
Interface Design Criteria (note 353) and Secondary Over Voltage Protection (note 324) application notes.
These notes are available from Dallas Semiconductor’s web site.
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