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 0.7

Ω 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 5

Ω 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.

Integrated T1/E1/J1 Short-Haul and

Long-Haul Protection Switch

8

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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.

Pin Description (continued)