AS5501 / AS5502 Multimode Powerline Modem
Data Sheet
With the bias-current outputs M1M and P1M the transistors T5 and
T6 get switched on and the driver stage is activated. The TxOut1,2 output-currents are in the
range of 3mA with complementary AC-components. For stability-reasons it is needed to
place a capacitor of 150pF from node VX to VSS.
The circuit with T1-T4 is a unity gain buffer structure. The transformer with attached
capacitor Cr gives a resonator for the used frequency-band.
With the shown test-circuit, the harmonic distortion has to be within the following limits with
a power-line load of (5ohms+50uH) // 50ohms:
ratio to the fundamental
2nd Harm.
3rd Harm.
higher Harm.
min. 70dB
min. 75dB
min. 80dB
100k
Rx
M1M
100
BC557
24V
24V
T5
BC557
24V
12
C2
6u8
BD139
T3
24V
RB
300
2k7
BC557
0V
24V
Cr
R1
13.3k
R2 18
10k
0.47u
LINE
1u
2.5:1
TXOUT1
TXOUT2
3k
C1
150p
VX
BD140
T1
Rx
100k
100k
Rx
Vout
0V
RB
2k7
BD139
T2
T4
BD140
12
C3
330p
R3
3k
0V
P1M
TXFB
RXIN
300
T6
BC547
0V
Cr has to be adjusted to proper Fcenter.
(RB, R1, R2, R3, C3 has to be adjusted
for 12V VBUF version.)
In receive-mode, when the bias-currents are turned off, the base of the two output-transistors
are forced by resistors of 100k (Rx) to 0V and Vbuf respectively to guarantee high impedance
of the buffer. The current of the pins TxOut1,2 is 0 (VX is floating). Since the receiver-AGC
is reacting on signal levels at the RXBPF-filter output, high outband noise-components could
give clipping in the first stages of the receiver path. To avoid this, aa attenuation of 16dB
with R2, R3, C3 is realized.
(Monochromatic Noise Measurement: Outband-noise with 0dBV @ line w. 80% AM (1kHz)
=> 12.8Vpp after transformer;
=> 2.0Vpp at pin RXIN; )
The resistors R1, R2, R3 are calculated to have a DC-voltages of Vbuf/2 at node Vout and
2.5V at node RXIN. An external diode for protection against high positive voltages is needed
at Vout (Pin TXFB).
Rev A, May 2000
Page 12/25
AMSCO [ AUSTRIAMICROSYSTEMS AG ]
