Datasheet

73M1866B/73M1966B Data Sheet DS_1x66B_001
32 Rev. 1.6
4.4 Isolation Barrier Pulse Transformer
The isolation element used by the 73M1x66B is a standard digital pulse transformer. Several vendors
supply compatible transformers with up to 6000 V ratings. Since the transformer is the only component
crossing the isolation barrier other than EMI capacitors that may be required, it solely determines the
isolation between the PSTN and the FXO’s digital interface. This method of isolation is significantly
superior to other isolation techniques with major advantages in high common mode voltage operation,
lower radiated noise (EMI) and improved operation in noisy environments. Table 29 lists some pulse
transformers compatible with the 73M1x66B. The table also includes low-voltage transformers that offer
low-cost alternatives if such voltages are sufficient.
Table 29: Compatible Pulse Transformer Sources
Company Number
Sumida ESMIT 4180
ESMIT 4181
Wurth Electronics Midcom Inc. 750110001
UMEC TG-UTB01543S
Datatronics PT79280
AAsupreme P950003
Table 30 lists some of the typical pulse transformer specifications used by the 73M1x66B. Contact the
manufacturer directly for product information.
Table 30: Pulse Transformer Electrical Characteristics
Parameter Test Condition Min Nom Max Tolerance Unit
Inductance 100 kHz, 10 mVAC, 1-2, Ls. 54 60 200 – μH
Interwinding
Capacitance
– – – 6 – pF
Turn Ratio – – 1:1 – ±2 % N/A
DC Resistance Primary – – 0.25 – Ω
Secondary – – 0.25 – Ω
Dielectric Breakdown
Voltage
1 sec 2000 3750 – – Vrms
ET Constant – – 1.2 – – Vμs
Surge Test 1.2 x 50 μs 2800 6000 – V
Operating Temperature – -40 – 85 –
°C