73M1903-IVT/F Maxim Integrated Products, 73M1903-IVT/F Datasheet - Page 41

• Manufacturer Part Number: 73M1903-IVT/F
• Description: IC MODEM AFE V.22BIS 20-TSSOP
• Manufacturer: Maxim Integrated Products

Specifications of 73M1903-IVT/F

• Number Of Channels: 2
• Voltage - Supply, Analog: 3 V ~ 3.6 V
• Voltage - Supply, Digital: 3 V ~ 3.6 V
• Package / Case: 20-TSSOP (0.173", 4.40mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -
• Number Of Bits: -

DS_1903_032
where
Use 1% resistors for R1, R2, and R3.
To select the value for C1, make the zero at around 10 Hz.
The blocking cap Cblock should also have the same frequency response, but due to the low impedance,
its value will be much higher, usually requiring a polarized cap. A blocking cap may also be needed on
the modem side of the transformer if the DC offset current of the transmit pins will exceed the current
rating for a dry transformer circuit.
If you are using a Wet transformer design, as in the following figure:
The only difference is that the blocking capacitor, Cblock, it is removed. All other equations still hold true.
Trans-Hybrid Loss (THL)
Trans-Hybrid Loss is by definition the loss of transmit signal from Tip/Ring to the receive inputs on the
modem IC. This definition is only valid when driving a specific phone line impedance. In reality, phone
line impedances are never perfect, so this definition isn’t of much help. Instead, as an alternate definition
that helps in analysis for this modem design, THL is the loss from the transmit pins to the receive pins.
Rev. 2.1
R3
Rwtot RW
R2 100 K
C1
C1 0.15 uF
Cblock
Cblock 27 uF
2 π . 100
.
1
2 π . 100
1
.
Rwtot
K C1
2 π . 600
100 K
.
1
1200
.
R3
K 10
1
Rohswitch
.
10
.
600
10
2 Rbead
.
73M1903 Data Sheet
41