Detailed Description

A common technique used to couple OFDM signals to

the AC powerline is through a signal transformer. A line

driver is needed to provide adequate levels of current and

voltage to drive the varying loads that exist on today’s

powerlines.

The MAX44211 line driver is efficient low-distortion power

amplifiers that drive high current to the low-impedance

loads common in powerline communication (PLC) appli-

cations. The output stage is designed to linearly drive up

to 1.5A peak current and a differential voltage of up to

meet the demanding requirements of today’s standards.

The MAX44211 also features two open-drain diagnostic

outputs, STATUS1 and STATUS0. These act as flags to

indicate the status of the part. Another significant feature

of the MAX44211 is its thermal monitoring and shutdown

capability. This allows the device to alert the host micro-

controller of high temperature situations and then to

automatically shut down to prevent damage should the

temperature rise further.

Output Enable

Enable the MAX44211 output by pulling TXEN high. The

amplifier outputs are fully enabled 2.4µs (typ) after TXEN

is pulled high. If a signal is applied to the IN+ and IN-

inputs during the startup time, it may be distorted and the

linearity specifications may not be met.

Bias MODE Selection

The MAX44211 linearity can be improved at the expense

of quiescent current. To meet CENELEC linearity require-

ments and save power, the MODE input is left uncon-

nected. To improve linearity and meet ARIB or FCC

requirements, the MODE input is pulled high.

Gain Selection and Output Connection

Set the MAX44211 overall gain using the G1 and G0

inputs (Table 1). The outputs, OUT+ and OUT- are inter-

swing. Therefore, the output should be A.C. coupled to

the coupling transformer to avoid DC currents flowing

in the transformer. In addition, the secondary side of the

transformer should also be AC-coupled to avoid shorting

the line input.

Protection and Diagnostics

The MAX44211 has two diagnostic status outputs:

STATUS0 and STATUS1. These are open drain outputs

that indicate the status of the device as shown in Table 2.

Both of the MAX44211 outputs are current limited. Set the

output current limit according to the following equation.

LIM

SET

60

I

R1

=

+

Operating Circuit).

Note that the tolerance for the current limit is ±30% so

care must be taken to ensure that the limit is set high

enough to avoid clipping at peak loads. In addition, if the

current limit is set too high, the device may enter thermal

shutdown mode.

PIN

NAME

FUNCTION

16

STATUS1

Open-Drain Active-Low Status Output1. See Table 2 for details.

17

STATUS0

Open-Drain Active-Low Status Output0. See Table 2 for details.

18

DGND

Digital Ground

19

IN+

Positive Signal Input

20

IN-

Negative Signal Input

—

EP

Exposed Pad. Internally connected to AGND. Connect the EP to a copper plane to enhance

thermal dissipation.

Table 1. Voltage Gain Selection

G1

G0

GAIN (V/V)

0

0

6

0

1

12

1

0

15

1

1

18

MAX44211

High-Current Differential Line Driver

for Powerline Communications

www.maximintegrated.com

Maxim Integrated │ 10

Pin Description (continued)