MAX4670 Datasheet, PDF (8/20 Pages) Maxim Integrated Products – Integrated T1/E1/J1 Short-Haul and Long-Haul Protection Switch

Integrated T1/E1/J1 Short-Haul and
Long-Haul Protection Switch
Pin Description (continued)
PIN
NAME
FUNCTION
22
NC4
Normally Closed Terminal 4. Transmitter 1 differential terminal. Connect NC4 to LIU receiver.
23
NO3
Normally Open Terminal 3. Transmitter 1 differential protection terminal. Connect NO3 to the
protection bus.
24
NC3
Normally Closed Terminal 3. Transmitter 1 differential terminal. Connect NC3 to LIU receiver.
25
NO2
Normally Open Terminal 2. Receiver 2 differential protection terminal. Connect NO2 to the
protection bus.
26
NC2
Normally Closed Terminal 2. Receiver 1 differential terminal. Connect NC2 to LIU receiver.
27
NO1
Normally Open Terminal 1. Receiver 1 differential protection terminal. Connect NO1 to the
protection bus.
28
NC1
Normally Closed Terminal 1. Receiver 1 differential terminal. Connect NC1 to LIU receiver.
29
COM1
Common Terminal 1. Receiver 1 positive differential terminal. Connect COM1 to the receive
interface transformer.
30
COM2
Common Terminal 2. Receiver 1 negative differential terminal. Connect COM2 to the receive
interface transformer.
31
INA
Receiver 1 Logic Control. Drive INA low to connect receiver 1 to the LIU. INA logic is ignored
when SWITCH asserts low.
EP
EP
Exposed Paddle. Connect EP to GND or leave unconnected.
Detailed Description
The MAX4670 is a quad-DPDT/octal-SPDT analog switch
optimized for T1/E1/J1 line-card redundancy protection
applications. This analog switch is configurable as two
differential transmitter and receiver pairs utilized in
T1/E1/J1 redundancy architecture.
The MAX4670 has four low 0.7Ω on-resistance switches
with 60pF and 40pF on- and off-capacitances, respec-
tively, for interfacing to the LIU transmitter inputs. The
MAX4670 also includes four 5Ω on-resistance switches
with low 24pF and 12pF on- and off-capacitances,
respectively, for interfacing to the LIU receiver inputs.
The MAX4670 replaces two diode arrays or two tran-
sient voltage suppressors and four dual-SPDT relays,
significantly reducing board space and simplifying PC
board routing. The MAX4670 pinouts are targeted for
T1/E1/J1 applications, resulting in a simplified layout
when interfacing with standard line transformers and
LIUs. Figure 1 is the functional diagram.
Logic Inputs (IN_, SWITCH)
The MAX4670 four logic inputs (IN_) control the switches
in pairs and contain a global logic input (SWITCH) that
connects all COMs to their respective NO_ inputs.
SWITCH overrides all IN_ inputs when asserted low, thus
connecting all NO_ to COM_ outputs (transmitter/receiver
pairs to the protection bus). When SWITCH asserts high,
IN_ controls the switch pairs. See Table 1.
Surge Protection
The MAX4670 includes chip-side, surge-protection capa-
bility for short-haul intrabuilding applications. The low-
capacitance diodes suppress surge residuals from the
primary, line-side protection devices. It is assumed that
adequate primary protection is included on the line die of
the transformer, as represented in Figures 7–10. Table 2
lists the applicable surge protection setups for E1
interfaces. The MAX4670 surge test was performed per
IEC 61000-4-5 Class 2 specifications and passed at ±1kV
with only an in-line transformer and primary surge sup-
pressor. The transformer was a Halo TG83-1505NX trans-
former and the surge suppressor was a Teccor P0640SC.
Applications Information
Redundancy Architecture
Figures 7 through 10 illustrate the MAX4670 used in two
different redundancy architectures. There is one back-
up card for up to N line cards in the system (in this
example, N = 3). In the event one of the line cards fails
(memory failure, power supply went down, etc.), a sys-
tem supervisory card issues a command to the switch-
es to reroute the traffic to and from the problem line
card to the backup line card.
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