AN4444 datasheet(62/68 Pages) STMICROELECTRONICS

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FAQ and troubleshooting

AN4444

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DocID025925 Rev 2

Problem: the ST7590 reference design board does not transmit.

What to check:

Check the bias voltage on the PA_OUT test point (TP2) with the oscilloscope

probe referred to VSS power ground. A DC voltage of VCC/2 must be measured.

Set the ST7590 in transmission via the PRIME GUI. A modulated signal should be

detected by the oscilloscope probe, with amplitude equal to the TX_OUT

programmed level multiplied by the PA gain (see Section 8.1.1: Line driver on

page 26). In this case, no problem is there about the transmitter section of the

ST7590.

Problem: the ST7590 reference design board transmits only for a short while; the

transmission is interrupted.

What to check:

Verify the external temperature of the ST7590 device.

Check if there is a short-circuit (i.e.: capacitive) impedance on the mains at the

carrier frequency. It could lead to the device overheating and PA thermal

shutdown.

Problem: the ST7590 reference design board does not receive.

What to check:

Check if the transmitted signal reaches the ST7590 device by measuring the RX_IN

line voltage (TP6) with the oscilloscope probe referred to VSSA signal ground.

Problem: During a communication test, the PRIME GUI shows high “Bit Error Rate”

(BER).

Note:

(This point refers to a half-duplex communication involving two ST7590 reference design

boards communicating with each other).

What to check:

Check that both reference design boards have the same PRIME GUI settings.

Verify the SNR of the communication. If the signal is too low or the noise is too

high with respect to each other, the communication performance will be poor. Try

to:

1. Check the SNR estimation of the receiving ST7590 device.

2. Measure the signal level S and the noise level N on the RX_IN line of the

receiving board.

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