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MAX13171E Datasheet, PDF (30/38 Pages) Maxim Integrated Products – Multiprotocol, Pin-Selectable Data Interface Chipset | |||
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Multiprotocol, Pin-Selectable
Data Interface Chipset
V.28 (RS-232) Interface
The V.28 interface is an unbalanced single-ended inter-
face (Figure 18). The V.28 driver generates a minimum
of ±5V across the 3k⦠load impedance between Aâ and
Câ. The V.28 receiver has a single-ended input.
The MAX13171E/MAX13173E V.28 mode receivers have
a threshold between +0.8V and +2.0V. To aid in reject-
ing system noise, the MAX13171E/MAX13173E V.28
receivers have a typical hysteresis of 250mV. Switch S3
in Figures 24a and 24b is closed in V.28 mode to enable
the 5k⦠V.28 termination at the receiver inputs.
V.35 Interface
Figure 25 shows a fully-balanced, differential standard
V.35 interface. The generator and the load must both
present a 100⦠±10⦠differential impedance and a
150⦠±15⦠common-mode impedance as shown by
the resistive T-networks in Figure 26. The V.35 driver
generates a current output (±11mA, typ) that develops
an output voltage of ±550mV across the generator and
load termination networks. The V.35 receiver is sensi-
tive to ±200mV differential signals at receiver inputs Aâ
and Bâ. The V.35 receiver rejects common-mode sig-
nals developed across the cable (referenced from C to
Câ) of up to ±4V, allowing for error-free reception in
noisy environments.
In Figure 26, the MAX13175E is used to implement the
resistive T-network that is needed to properly terminate
the V.35 driver and receiver. Internal to the
MAX13175E, S1 and S2 are closed to connect the T-
network resistors to the circuit. The V.28 termination
resistor (internal to the MAX13171E) is disabled by
opening S3 to avoid interference with the T-network
impedance.
The V.35 specification allows for ±4V of ground differ-
ence between the V.35 generator and V.35 load. The
MAX13174E maintains correct termination impedance
over this condition.
Aâ² A
R5
55kâ¦
R8
5kâ¦
R6
11kâ¦
S3
Bâ² B
+-
1.4V
R7
11kâ¦
R4
55kâ¦
S1
Câ²
S2
GND
MAX13171E
MAX13173E
RECEIVER
Figure 24a. V.28 Termination and Internal Resistance Network
for Receiver 1, 2, and 3
Aâ² A
R5
55kâ¦
R8
5kâ¦
R6
11kâ¦
S3
MAX13173E
RECEIVER
Câ²
GND
Figure 24b. V.28 Internal Resistance Network for Receiver 4
and 5
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