UC864-E Hardware User Guide
1vv0300766a Rev.1 - 31/01/08
10.4.2 Output lines (speaker)
During designing, remember that while no difference could be if the amplifiers drive an external amplifier, there are slightly different electrical performances when the load is driven directly from the internal audio amplifiers, due to differential output voltage.
| Line coupling |
|
|
| DC |
|
| Line type |
|
|
| Differential |
|
| Output load resistance |
|
|
| 32 Ω |
|
| Max. Load capacitance |
|
|
| 500pF(max) |
|
| Differential output impedance |
|
|
| 1 Ω (max) @ 1.02KHz |
|
| Signal bandwidth |
|
|
| 150 - 4000 Hz @ |
|
| Differential output voltage @ 0dBm0 |
|
| 1.06 Vrms (typical) |
| |
| Number of volume steps |
|
|
| 10 |
|
| Volume level step |
|
|
|
| |
| Table 3. | “Ear_MT” Buffers |
| |||
|
|
|
|
| ||
Line coupling |
| DC |
| |||
Line type |
|
| Differential |
| ||
Output load resistance |
|
| 32 Ω |
| ||
Max. load capacitance |
|
| 500pF(max) |
| ||
Differential output resistance |
|
| 1 Ω (max) @ 1.02KHz |
| ||
Signal bandwidth |
|
| 150 - 4000 Hz @ |
| ||
Differential output voltage @ 0dBm0 |
| 833mVrms (typical) |
| |||
Number of volume steps |
|
| 10 (SW) |
| ||
Volume level step |
|
|
| |||
| Table 4. | “Ear_HF” Buffers |
| |||
We suggest to drive the load differentially from both receive drivers, thus the output swing is doubled and the need for the output coupling capacitor is eliminated. However for particular OEM application needs also a Single Ended circuitry can be implemented, but reducing by four the output power.
The OEM circuitry shall be designed to reduce the common mode noise typically generated on the ground plane and to get the maximum power output from the device (low traces resistance).
Audio amplifiers could be design in two configurations: balanced (or differential) and unbalanced (or
The differential output power amplifier configuration is also called BTL
In the following a discussion about the use of the two input and output amplifier configurations will be dealt with.
Also calculation and circuit examples will be exhaustively performed.
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved | page 40 of 51 |