MC145572APB Freescale Semiconductor, MC145572APB Datasheet - Page 14

• Manufacturer Part Number: MC145572APB
• Description: IC ISDN INTERFACE TXCVER 44-LQFP
• Manufacturer: Freescale Semiconductor
• Type: Transceiverr

Specifications of MC145572APB

• Protocol: RS232
• Voltage - Supply: 5V
• Mounting Type: Surface Mount
• Package / Case: 44-LQFP
• Number Of Line Interfaces: 1
• Control Interface: HDLC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Number Of Drivers/receivers: -
• Lead Free Status / Rohs Status: Not Compliant

required for the MC145572 oscillator. All other frequency pulling circuitry is internal to the MC145572.
is required to provide protection, while not adversely affecting the S/T-interface when power is removed
from the device. This diode structure also protects the circuit against electrostatic discharges (ESD) and
latch-up.
The S/T-Interface Transceiver implementation on this board can be used in either NT or TE mode. Pin 4,
D-Channel data in the next IDL D time slot. In the NT mode, pin 6 performs the FIX and TFSC functions.
FIX tells the S/T-Interface Transceiver to use Fixed or Adaptive timing recovery. TFSC is asserted when
manual.
With the left side of the board operating as an NT1, the MC145574 S/T-Interface Transceiver is in the NT
mode, operating as an IDL Slave, and is receiving its Clock and Sync signals from the MC145572
2.1.2
In the LT mode, the internal phase locked loop (PLL) of the MC145572 generates a 20.48 MHz clock which
is phase locked to an 8 kHz reference clock applied at the FREQREF pin. This assures that the transmitted
2B1Q signal is synchronized to the 8 kHz frequency reference. A single pullable crystal, Y1, is all that is
It is also possible to provide an external 8 kHz frequency reference rather than using the 8 kHz frequency
reference generated on-board from the 5 ppm oscillator, Y5. This is accomplished using the RF
switch of S2-1 and connecting the external reference to EXTREF of J9. RF
frequency reference and RF
for S2-1 and S2-7 in Section 2.7.2.
2.1.3
The NT-conÞgured MC145572 U10, requires only a single pullable crystal, Y2, for its oscillator. All other
frequency pulling circuitry is internal to the MC145572.
2.2
The S/T-Interface resides on the NT1 portion of the MC145572EVK and is implemented using the
MC145574 S/T-Interface Transceiver (U17). The 600 mil 28-pin Plastic SOIC MC145574 conforms to both
CCITT I.430 and ANSI T1.605 speciÞcations. External line interface circuitry for switching between NT
and TE operating modes is incorporated.
Two 8-pin RJ-45 telephone jacks are used at the S/T-Interface, one conÞgured for the NT mode (J24) of
operation and one conÞgured for the TE mode (J23) of operation. The Tx pair, pins 4 and 5 on the NT jack
and pins 3 and 6 on the TE jack, are driven by the TxP and TxN pins which act as a current limited differential
voltage source. The drive resistance (R40, R42) is necessary to conform to the ANSI T1.605 pulse mask
speciÞcation. A dual 2.5:1 turns ratio transformer (T4A:B) is used to couple the Tx and Rx pairs to the
4-wire interface. A high frequency 4-wire common mode choke transformer (T3 for TE and T5 for NT)
provides an effective means of compliance with EMI suppression.
The protection diodes (D29A:G, D30A:G MMAD1108) provide secondary protection to the MC145574,
even when it is powered down, without loading the S/T-Interface bus. CCITT I.430, ETSI ETS 300012, and
ANSI T1.605 specify that the S/T-interface voltage cannot exceed 1.6 times the nominal voltage of 750 mV
(= 1.2 V). Since the MC145574 is designed to operate with 2.5:1 turns ratio transformers, the diode structure
TE/NT(L), of the MC145574 determines whether the chip is in NT or TE mode of operation. When
conÞgured as a TE, pins 9 and 8 are used as DREQUEST and DGRANT, respectively. The DREQUEST
pin is used by an external controller such as the MC145488 DDLC or the MC68302 IMP to request access
to the D-Channel. When the S/T-Interface Transceiver gains access to the D-Channel time slot on the
S/T-Interface bus, it asserts DGRANT high, informing the external controller that it can transmit its
frame synchronization has been achieved at the S/T-Interface bus. For a more complete discussion on
D-Channel operation, please refer to Section 11 of the MC145574/75 S/T-Interface Transceiver data
S/T-INTERFACE
Crystal Oscillator (LT Mode)
Crystal Oscillator (NT Mode)
Freescale Semiconductor, Inc.
on
For More Information On This Product,
selects the on-board 8 kHz frequency reference. See also the explanation
Go to: www.freescale.com
off
selects the off-board 8 kHz
MC145572EVK
off
-RF
15
on