73M1866B-IM/F Maxim Integrated Products, 73M1866B-IM/F Datasheet - Page 4

• Manufacturer Part Number: 73M1866B-IM/F
• Description: MICRODAA SGL PCM HIGHWAY 42-QFN
• Manufacturer: Maxim Integrated Products
• Series: MicroDAA™r

Specifications of 73M1866B-IM/F

• Includes: PCM Highway
• Function: Data Access Arrangement (DAA)
• Interface: PCM, Serial, SPI
• Number Of Circuits: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 42-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Power (watts): -

73M1866B/73M1966B Schematic and Layout Guidelines
•
Connections to Tip and Ring
A current limiting device (F1 as shown in Figure 4) is a highly recommended protection component to limit turn-on
transient voltage and current for GR-1089-CORE 2500 V and FCC part 68 1500 V impulse tests (this device is
bypassed for some power cross tests). Some, but not all, thyristor devices (E1 as shown in Figure 4) must have
an additional minimum series resistance to survive the more stringent certification tests. The higher on resistance
of Plastic Positive Temperature Coefficient (PPTC) fuse devices (F1) can serve this purpose and improve product
reliability compared to other current-limiting components because they automatically reset after a fault condition is
removed. The cost of PPTC devices is comparable to single event slow-blow fuses designed for telecom
applications. It is possible to avoid fuses altogether if the product is in a fire enclosure and is supplied with a 26
AWG or larger RJ-11 telephone cable. But if this route is chosen, the reliability, potential fire and damage to the
other circuits in the enclosure should also be considered.
The ratings for the protection devices depend on a country’s requirements for safety testing as well as the ringing
voltage and DC source voltage. For the U.S., the requirements are more stringent that for most other countries.
The UL over voltage tests require passing 600 V, 60 A tests, so the PPTC fuse must have a 600 V rating. For
most other countries’ applications this only needs to be 250 V. The U.S. tests require testing with a CO battery
voltage of 56 V and 150 Vrms ringing, so the peak voltage is 268.8 V. This means the thyristor must not trigger
on these ringing voltages, so minimum voltage the voltage protection can trigger at must be at least that voltage,
meaning a 270 V or 275 V thyristor must be used since that is the next larger standard minimum breakdown
voltage that is made. In countries where the DC loop and ring voltages are lower than this, a lower voltage
thyristor can be used instead.
Ring Detect and Caller ID Path
The components in the input circuit to the Ring Detect and Caller ID (RGN and RGP) pins of the line-side device
are used to provide attenuation to this function. The attenuation required means the RGN/RGP inputs will have a
high impedance and are sensitive to noise pick-up. The high impedance-side traces to the components must be
kept short. Resistors used in the ring detection circuit (R66 and R68 in Figure 4) must be a minimum of 0805 size
to meet the voltage rating requirements of the line-side connections to the network. Similarly the capacitors (e.g.
C1 and C3) require a voltage rating of at least 200 V to withstand the ringing and battery voltages. Any capacitors
that bridge Tip and Ring need to be rated at least 275 VAC. Locate these resistors and capacitors as close as
possible to the 73M1916 Line-Side Device (or the Line-Side of the 73M1866B) to reduce noise pick-up and
achieve the best possible performance.
As previously stated, keep all analog signal traces separate from high-speed digital circuitry and traces. The
barrier interface has relatively large, high-current signals when the 73M1916 Line-Side Device is in an operational
mode. Signal traces to the RGN and RGP pins need to be kept physically separated from the barrier.
Pulse Transformer Considerations
Table 1 provides a list of pulse transformers that have been tested and proven to work with the 73M1x66B device.
4
Company
Sumida
Wurth Electronics
Midcom Inc.
UMEC
Datatronics
To minimize unwanted series inductance, do not use PCB vias between the 1000 pF bypass capacitors and
device pins.
Number
ESMIT 4180
ESMIT 4181
750110001
TG-UTB01543S
PT79280
Table 1: Validated Transformers for Use with the 73M1x66B
Rated Isolation
6 kV peak
(Dielectric 3750 Vrms min)
6 kV peak
(Dielectric 3750 Vrms min)
6 kV peak
(Dielectric 3750 Vrms min)
6 kV peak
(Dielectric 3750 Vrms min)
Typ. Inductance Typ. Interwinding
120 µH min
60 µH min
150 µH min
150 µH min
60 µH min
Capacitance
5 pF max.
Not specified
Not specified
2.5-5 pF
AN_1x66B_003
Rev. 3.5