20

¡ Semiconductor

ML7021

NOTES ON USE

1. Set echo return loss (ERL) to be attenuated. If the echo return loss is set to be

amplified, the echo can not be eliminated.

Refer to the characteristic diagram for ERL vs. echo attenuation quantity.

2. Set the level of the analog input so that the PCM CODEC does not overflow.

3. The recommended input level is –10 to –20 dBm0. Refer to the characteristic

diagram for the RIN input level vs. echo attenuation quantity.

4. Applying the tone signal to this echo canceler for long duration may decrease echo

attenuation.

When used with the HD pin "L" (howling detector ON), this echo canceler may

operate faultily if, while a signal is input to the RIN pin, a tone signal with a higher

level than the signal being input to RIN is input to the SIN pin.

A signal should therefore be input either to the RIN pin or to the SIN pin. If,

however, the tone signal is input to the SIN pin while a signal is input to the RIN

pin, the ADP, HD, or HCL pin must be set to "H".

5. For changes in the echo path (retransmit, circuit switching during transmission,

and so on), convergence may be difficult.

Perform a reset, to make it converge.

If the state of the echo path changes after a reset, convergence may again be

difficult.

In cases such as a change in the echo path, perform a reset each time.

6. When turning the power ON, set the PWDWN pin to "1" and input the basic clock

simultaneously with power ON.

If powering down immediately after power ON, be sure fast input 10 or more

clocks of the basic clock.

7. After powering ON, be sure to reset.

8. After the power down mode is released (when the PWDWN pin is changed from

"L" to "H"), be sure to reset the device.

9. If this canceler is used to cancel acoustic echoes, an echo attenuation may be less

than 30 dB.